# Print reading question



## jbonfoey (Jul 8, 2020)

On the attached picture does the line referencing the countersink mean to make the top (largest part) of the countersink hole .225 in diameter? I made it .225 deep using an 82-degree countersink and it’s huge for a 4-40 FH screw.  Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole? 

Using an iPad and can’t find some of the characters on the print.  Thanks for help with dumb question. 

Math challenged.
Jack


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## Barnbikes (Jul 8, 2020)

It is telling you to drill a .116" hole. Then take your 82 degree countersink and make the top of the hole .225 diameter.

Way I teach guys at work is take hole size subtracted from countersink size. Divide that number by 2. Take your caliper and mark that distance on both sides of the hole and countersink to that mark. 
.225" - .116" = 109
.109"/2 = .0545"


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## jbonfoey (Jul 8, 2020)

Thanks Barnbikes, that seems quite straight forward.


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## SmithDoor (Jul 8, 2020)

I fit the counter sink to fit the screw.
The only time I worry about want the drawing say if I doing work for some else.

Dave



jbonfoey said:


> On the attached picture does the line referencing the countersink mean to make the top (largest part) of the countersink hole .225 in diameter? I made it .225 deep using an 82-degree countersink and it’s huge for a 4-40 FH screw.  Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole?
> 
> Using an iPad and can’t find some of the characters on the print.  Thanks for help with dumb question.
> 
> ...


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## jbonfoey (Jul 9, 2020)

Thanks SmithDoor, makes sense. I guess maybe in the back of my mind I was hoping I hadn’t ruined the piece I was countersinking....but to no avail.


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## SmithDoor (Jul 9, 2020)

A complete drawing will even have the finish for each operation.
Some times it give statement unless otherwise the finish is to be ######.
I do not outside the drafting class I seen a complete drawing for machining.

My self most life all my work was in shop. 
The only time I had worry about drawing details is sending out work.
I did work for few years work shops and drawing that came in the door was a real mess.
Statement like fit ball bearing with no other details. 

Dave



jbonfoey said:


> Thanks SmithDoor, makes sense. I guess maybe in the back of my mind I was hoping I hadn’t ruined the piece I was countersinking....but to no avail.


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## jbonfoey (Jul 9, 2020)

Well, thank you again SmithDoor. I’m learning as I go, and I’ve learned about the countersinking process today. Seems I often learn by mistakes anymore, but since this is my hobby mostly it’s time I waste.
Take care,
Jack


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## Richard Hed (Jul 10, 2020)

jbonfoey said:


> Well, thank you again SmithDoor. I’m learning as I go, and I’ve learned about the countersinking process today. Seems I often learn by mistakes anymore, but since this is my hobby mostly it’s time I waste.
> Take care,
> Jack


You might also remember thant counter-sinkings purpose is USUALLY to have the screw below the surface and that is all that is needed__usually.  Occasssionally there is some other purpose but on models, this is probably the purpose to just get the screw below the surface.


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## jbonfoey (Jul 11, 2020)

Yes, good reminder Richard, thanks. These happen to be quite obvious, so I’ve remade the part.


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## Rugbyears (Jul 11, 2020)

jbonfoey said:


> Well, thank you again SmithDoor. I’m learning as I go, and I’ve learned about the countersinking process today. Seems I often learn by mistakes anymore, but since this is my hobby mostly it’s time I waste.
> Take care,
> Jack


I appreciate it can be quite frustrating, but remain positive as mistakes are a useful way of learning. If you make a mistake, you seldom make the same one. If it is a hobby, enjoy yourself, life is to short to fret over a silly mistake. Remind yourself the next time you’ve made a mistake that you’ve just learn something new.  I am a complete newbie, and am prone to making mistakes, but what a wonderful opportunity to be able to learn and engage with all you knowledgeable and skilled people


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## easymike29 (Jul 12, 2020)

jbonfoey said:


> Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole?


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## BillC (Jul 12, 2020)

Trigonometry - all (most all) hand held calculators have trig functions. Tangent of 41 degrees = .869286. From there basic math. Then touch off the countersink on a suitable shim and plunge the hole for the countersink size needed. Handy for multiple holes for consistency.
Your drawing shows the depth as .0627" which will not result in a .225" dia. countersink.
Rough sketch:


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## BillC (Jul 12, 2020)

Your drawing shows the depth as .0627" which will not result in a .225" dia. countersink.


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## kinggt4 (Jul 12, 2020)

Easymike29 and Billc are both correct.  Easymike is not showing the full depth of the tountersink travel as Bill is.


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## easymike29 (Jul 16, 2020)

BillC said:


> Trigonometry - all (most all) hand held calculators have trig functions. Tangent of 41 degrees = .869286. From there basic math. Then touch off the countersink on a suitable shim and plunge the hole for the countersink size needed. Handy for multiple holes for consistency.
> Your drawing shows the depth as .0627" which will not result in a .225" dia. countersink.
> Rough sketch:



I believe you need to rethink your logic on the total travel. I could be wrong.
Eugene


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## BillC (Jul 16, 2020)

I wasn't really giving precise data but the means of acquiring it. My math is probably all wrong just as the wish to help out on this forum. I need counseling too... I've made out OK for 72 years without smart ass comments from here so my help of any sort will be curtailed completely. I'm away from this forum - no reply needed any longer.


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## Bentwings (Jul 17, 2020)

BillC said:


> I wasn't really giving precise data but the means of acquiring it. My math is probably all wrong just as the wish to help out on this forum. I need counseling too... I've made out OK for 72 years without smart ass comments from here so my help of any sort will be curtailed completely. I'm away from this forum - no reply needed any longer.





BillC said:


> I wasn't really giving precise data but the means of acquiring it. My math is probably all wrong just as the wish to help out on this forum. I need counseling too... I've made out OK for 72 years without smart ass comments from here so my help of any sort will be curtailed completely. I'm away from this forum - no reply needed any longer.


I don’t want to enter an argument. I haves black book that has another every calculation needed for machine work it compliments machinery’s manual. I simply look up what is needed. Some times posing the question to look in the index is harder than doing the work, it’s been in my machine toolbox for 20 years or more once I got to cad it was more of constructing the simple model then adding what ever dim. I needed my current cad can go to 14 decimal places if necessary. But I don’t do that except to impress the nay sayersLOL


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## jbonfoey (Aug 3, 2020)

Thanks you all for your input everyone, I’ve printed out the diagrams and hopefully learn something.


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## SmithDoor (Aug 3, 2020)

Drill dia is 0.116
Counter sink dia 0.225 @ 82°

Dave



jbonfoey said:


> On the attached picture does the line referencing the countersink mean to make the top (largest part) of the countersink hole .225 in diameter? I made it .225 deep using an 82-degree countersink and it’s huge for a 4-40 FH screw.  Is there a quick (and easy) way to know how deep to drill with a 82-degree countersink to get a .225 diameter hole?
> 
> Using an iPad and can’t find some of the characters on the print.  Thanks for help with dumb question.
> 
> ...


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## easymike29 (Aug 4, 2020)

jbonfoey said:


> Thanks you all for your input everyone, I’ve printed out the diagrams and hopefully learn something.



If you copied BillC's sketch you should know that the use of  (a = b x Tan B) is not correct in this instance.
Eugene


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## Cogsy (Aug 5, 2020)

BillC said:


> Trigonometry - all (most all) hand held calculators have trig functions. Tangent of 41 degrees = .869286. From there basic math. Then touch off the countersink on a suitable shim and plunge the hole for the countersink size needed. Handy for multiple holes for consistency.
> Your drawing shows the depth as .0627" which will not result in a .225" dia. countersink.



As has been said, the math here is slightly mixed up. Using Bill's sketch, we do indeed want to find the dimension of 'a' and as it stands we know angle 'B'  (41 degrees being 1/2 82 degrees) and side 'b' at 0.1125". Bill is also correct that we need to use tan(B), which is ~0.869. However, remember from SOH CAH TOA that tan is Opposite/Adjacent sides.

So therefore tan(B) = b/a 
if we multiply both sides by 'a' we get 'a * tan(B) = b'
then divide both sides by tan(B) and we get  'a = b/tan(B)'
which means 'a = 0.1125/0.869  =>  a = 0.129'.

So touch off your cutter on the surface then plunge 0.129" and you should have the feature your drawing calls for.


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## willray (Aug 6, 2020)

Cogsy said:


> As has been said, the math here is slightly mixed up. Using Bill's sketch, we do indeed want to find the dimension of 'a' and as it stands we know angle 'B'  (41 degrees being 1/2 82 degrees) and side 'b' at 0.1125". Bill is also correct that we need to use tan(B), which is ~0.869. However, remember from SOH CAH TOA that tan is Opposite/Adjacent sides.
> ...



This is mildly an aside, but - you gentlemen do realize that the reason there's an argument going on here, is because that .0627 dimension should never have been provided on a drawing?

There was a recent argument either here, or on PracticalMachinst (can't remember which) where a large portion of the respondents were adamant about how drawings ought not to be properly dimensioned (only those dimensions provided that are necessary to derive all the rest), but rather that every possible redundant dimension should be provided as well. The myriad of problems that are caused by over-dimensioning a print, carried no weight in that discussion.

Well, this argument is one of those problems.

The .0627 dimension is correct - for the depth of the truncated-cone portion of the countersink.

Since the 0.225 dimension, and the 82 degree countersink are the defining features, and all the rest of the dimensions can be calculated from them, none of the rest of the dimensions should have been provided.  That the 0.0627 dimension was provided - an absolutely useless dimension[*] to the machinist - served no purpose other than to confuse the issue.

[*] Useless, except for the fact that one could calculate the full depth from it, without needing trig:  By similar triangles, the 0.0627 length is the "height" of triangle A, where the "base" of triangle A is 0.225/2.0 minus 0.116/2.0 ( 0.1125 - 0.058 = 0.0545).  Triangle B is a similar triangle where its height "d" is your total plunge depth, and its base is 0.1125.  Similar triangles are just ratio problems, so d = 0.1125/0.0545 * 0.0627 = 0.1294







Still, if that (0.0627) dimension is provided, the countersink angle is redundant, and it would seem to be the more critical dimension.  I'm mostly providing this illustration so the "math challenged" can see there's an answer that they can probably reason their way to, even if trig seems challenging.


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## easymike29 (Aug 6, 2020)

willray said:


> This is mildly an aside, but - you gentlemen do realize that the reason there's an argument going on here, is because that .0627 dimension should never have been provided on a drawing?
> 
> 
> View attachment 118424



The .0627 dimension was never on the drawing. It was provided by me in answer to the OP's request for a down and dirty method of fulfilling the requirements of the c'sink specs. I stand by my procedure. Drill the hole to size. Replace the drill with the c'sink. Lower the c'sink untill it just touches the thru hole. Plunge .0627. I purposely did not supply any trig. That is another matter.

Eugene


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## Richard Hed (Aug 6, 2020)

willray said:


> This is mildly an aside, but - you gentlemen do realize that the reason there's an argument going on here, is because that .0627 dimension should never have been provided on a drawing?
> 
> There was a recent argument either here, or on PracticalMachinst (can't remember which) where a large portion of the respondents were adamant about how drawings ought not to be properly dimensioned (only those dimensions provided that are necessary to derive all the rest), but rather that every possible redundant dimension should be provided as well. The myriad of problems that are caused by over-dimensioning a print, carried no weight in that discussion.
> 
> ...


Yes, I would have done it completely different too:  I would use the Pythagorean Theorem then finish with what you have done.  BTW, the trigonomic identity Sin (x) 2 + Cos(x) 2 = 1, (those twos stand for "squared"), is the same as the Pythagorean Theorem just in a different form.  Both work equally well, but somethimes you have an angle and other times you have two lengths of the legs of the triangle.


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## willray (Aug 6, 2020)

easymike29 said:


> The .0627 dimension was never on the drawing. It was provided by me in answer to the OP's request for a down and dirty method of fulfilling the requirements of the c'sink specs. I stand by my procedure. Drill the hole to size. Replace the drill with the c'sink. Lower the c'sink untill it just touches the thru hole. Plunge .0627. I purposely did not supply any trig. That is another matter.
> 
> Eugene



Ok, I'll soften my "completely useless" assessment. I hadn't thought of touching off on the diameter of the hole with a centered countersink, and then plunging the additional 0.0627.  That certainly gets you where you need to be as well.

If I were dimensioning a drawing imagining that the machinist might take that approach, I would have provided the 82 degree countersink, and the 0.0627 additional plunge depth, rather than the .225 diameter.


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## Richard Hed (Aug 6, 2020)

willray said:


> Ok, I'll soften my "completely useless" assessment. I hadn't thought of touching off on the diameter of the hole with a centered countersink, and then plunging the additional 0.0627.  That certainly gets you where you need to be as well.
> 
> If I were dimensioning a drawing imagining that the machinist might take that approach, I would have provided the 82 degree countersink, and the 0.0627 additional plunge depth, rather than the .225 diameter.


I still maintain that the only purpose this whole countersink serves is to put the screw head below the surface of the plate (or what ever).  So what does it matter if you go 10thou over?  10 thou isn't even the thickness of a finger nail.  If you want perfection on such a thing, then set your drill stop.  Occassionally, the screw will be in a place one does indeed wish for it to look nice, and that is where it will be seen prominentlhy on a polished finish or whatever.  THen, one might wish for it to be exact.


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## deeferdog (Aug 6, 2020)

For me, put as many dimensions as possible. Plans should be a set of instructions, not a maths exam. Cheers, Peter


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## Richard Hed (Aug 6, 2020)

deeferdog said:


> For me, put as many dimensions as possible. Plans should be a set of instructions, not a maths exam. Cheers, Peter


I absolutely agree with that.  Put in all the important, necessary dimensions but don't over do it.  I have the Ray/Corliss original dwgs.  By today's standards they are absolutely KRAP.  Over dimensioned up to 4, even 5 times.  It made the prints nearly unreadable.  This was all hand drawn and could have been so much more readable had he only dimmed each dim once.  The dims from one part would overlap the next part and one didn't know what the dim was dimming.  Even so, I GREATLY admire the drawings as a work of art.

BTW, I took some photos of the RAY drawings and could not get the lines to darken enough.  Recently I managed to darken them.  If this forum will accept them, I will put one up and you can examine it.---well krap, I have to find them first.


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## Richard Hed (Aug 6, 2020)

OK, if you blow them up a lot, you can read them.  Altho' they tend to be rather blurry.  Someday, I might be able to afford a camera.

there are 8 more if anyone is intersted.


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## easymike29 (Aug 6, 2020)

Cogsy said:


> ...........So touch off your cutter on the surface then plunge 0.129" and you should have the feature your drawing calls for.



Yes and no. For this to be true the c'sink would need to have a dead sharp point. If it had even a .005" radius the mouth diameter would be oversize by .0045. Trivial maybe but needs to be taken into consideration if working within tolerances. It's not a good idea to try to second guess the engineer or designer.

Eugene


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## lennardhme (Aug 7, 2020)

Eugene said...    It's not a good idea to try to second guess the engineer or designer. 
I believe it is;  or how can things be improved?
I don't think I've ever built an engine exactly to specs....depends on materials, my mood at the time & a host of other things.....unless of course you are building for someone else [a job]
This is model engine club & I think most of the best models have some innovation & individuality. [IMO of course] 
Have fun,
cheers,
Lennard.


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## Peter Twissell (Aug 7, 2020)

easymike29 said:


> Yes and no. For this to be true the c'sink would need to have a dead sharp point. If it had even a .005" radius the mouth diameter would be oversize by .0045. Trivial maybe but needs to be taken into consideration if working within tolerances. It's not a good idea to try to second guess the engineer or designer.
> 
> Eugene


Mike, the suggestion is not to touch the point of the countersink on the surface, but to touch its cutting edge on the edge of the drilled hole.


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## easymike29 (Aug 7, 2020)

Peter Twissell said:


> Mike, the suggestion is not to touch the point of the countersink on the surface, but to touch its cutting edge on the edge of the drilled hole.



Yes, Peter that is my method  but I was replying to a posting by Cogsby. There is also a  likelihood that an error would occur if the thru hole is not to size. That also needs to be accounted for if working to tolerances. If you're working for a customer get his/her approval for any variances first.

Eugene


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## easymike29 (Aug 7, 2020)

lennardhme said:


> Eugene said...    It's not a good idea to try to second guess the engineer or designer.
> I believe it is;  or how can things be improved?
> I don't think I've ever built an engine exactly to specs....depends on materials, my mood at the time & a host of other things.....unless of course you are building for someone else [a job]
> This is model engine club & I think most of the best models have some innovation & individuality. [IMO of course]
> ...



Lennard, of course you're encouraged to be innovative. You can still do that when working for a customer, just don't try it without consulting with whomever is authorized to implement what you are proposing. Your customer will in most cases be appreciative especially if it can improve his bottom line. Engineers/designers do not deliberately try to make parts difficult for the machinist to fabricate. In any case bid on the part as toleranced or pass on it.

Eugene


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## Asm109 (Aug 7, 2020)

Stepping up onto the soap box...............

The drawing is the embodiment of the designers, wait for it... , design intent.  It should completely describe the part and all the tolerances required for the part to function the way the designer intended.  The part should also be able to be inspected to the print after fabrication.  The how of making the part belongs on Process sheets and other fabrication information, NOT cluttering up the drawing.


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## William May (Aug 7, 2020)

In this case, the DESIGNER should have done the trig, and not made the machinist's into designers. HE should have determined what it takes to create the .225 diameter he is  calling out, and provided means to do it. Almost every dimension on that crappy drawing could have been skipped, if the designer had done the  work he should have done.
The drawing should simply have stated: *82 degree countersink, .129 deep" That is all that is needed to generate the correct hole. 
If YOU have to do calculations to figure out what the designer meant, then HE did not do his job. 
If HE does it ONCE, then that means that 4000 other people don't have to ALSO DO IT.
Every time you require something to be figured out, you give an excellent opportunity for an error or a misinterpretation.


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## willray (Aug 7, 2020)

William May said:


> The drawing should simply have stated: *82 degree countersink, .129 deep" That is all that is needed to generate the correct hole.



Not to be entirely contrary, but, there is a huge difference between instructions, and a design specification.

What you are asking for are instructions.  There's nothing wrong with instructions, but, that's not typically the designer's, or draftsman's job.   A good designer or draftsman may (should) anticipate the most common approach to machining a feature, and choose a strategy for dimensioning the feature so that the important details for the machining approach can be picked off the print easily, but the _design_specification_ should not rely on a particular machining approach to arrive at correct dimensions, nor obfuscate landmarks necessary to check the part against the print.

How would you propose to use your "82 degree countersink, .129 deep" instruction, to check parts against the print to determine if they are to spec?  (The problem being, the missing apex of the countersunk hole, for validation-measurement purposes).


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## William May (Aug 7, 2020)

willray said:


> Not to be entirely contrary, but, there is a huge difference between instructions, and a design specification.
> 
> What you are asking for are instructions.  There's nothing wrong with instructions, but, that's not typically the designer's, or draftsman's job.   A good designer or draftsman may (should) anticipate the most common approach to machining a feature, and choose a strategy for dimensioning the feature so that the important details for the machining approach can be picked off the print easily, but the _design_specification_ should not rely on a particular machining approach to arrive at correct dimensions, nor obfuscate landmarks necessary to check the part against the print.
> 
> How would you propose to use your "82 degree countersink, .129 deep" instruction, to check parts against the print to determine if they are to spec?  (The problem being, the missing apex of the countersunk hole, for validation-measurement purposes).



NO, I'm NOT asking for instructions. I'm asking for the designer to finish his work properly.  
If it WAS necessary to check the spec, you don't need the apex.  All you need is a go/no-go gauge to drop in the countersink and see if it is correct.  In this case, you don't care about the size of the hole. All you care about is making sure the countersink is to spec. 
If EVERY person who uses the drawing has to do MORE calculations to determine what the designer really intended, then it's a BAD DRAWING.
I experienced this every day in working on aircraft. 
You should CLEARLY state the design in your drawing. If the detail you are presenting needs further calculation and work, then the drawing is NOT FINISHED. 
I work a LOT with very early machine drawings, on both locomotives and automobiles, all from before 1920. I can say universally, that these drawings are complete in every detail. People who think CAD drawings are great would tremble after looking at one of them, they are so beautifully done. 
Like I said, if every person who uses that drawing has to do calculations to find out where to go, the drawing is NOT finished and useable.


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## willray (Aug 7, 2020)

William May said:


> NO, I'm NOT asking for instructions. I'm asking for the designer to finish his work properly.
> If it WAS necessary to check the spec, you don't need the apex.  All you need is a go/no-go gauge to drop in the countersink and see if it is correct.  In this case, you don't care about the size of the hole. All you care about is making sure the countersink is to spec.



And what is the correct go/no-go gauge, if the drawing specifies "82 degree countersink, .129 deep" 



> If EVERY person who uses the drawing has to do MORE calculations to determine what the designer really intended, then it's a BAD DRAWING.



I don't think we're that far apart on this, however, in any drawing more complicated than a single line, clearly conveying the design intent _requires_ leaving some dimensions for the end-user to calculate.  The clever designer minimizes these, but a drawing with 2 or more dimensions either has some omitted dimensions, or, it's over-dimensioned and therefore both prone to a myriad of potential errors, as well as impossible to use to actually determine the design intent.



> You should CLEARLY state the design in your drawing. If the detail you are presenting needs further calculation and work, then the drawing is NOT FINISHED.



The drawing should clearly state the feature/product specification.  In the case of a countersunk hole, the specification is for a cone coaxial with a hole, the cone having a particular included angle, and either being some width at the surface of the piece, or, sunk to some depth below the surface of the piece.  More than those two dimensions (angle, and either width, or depth), and the feature is overspecified, and the design intent can no-longer be interpreted.

Since there are a myriad of ways to produce said feature, a specification of "82 degree countersink, .129 deep" would be a particularly poor specification.  That's an instruction, and applies to not just one machining method, but to only one type of countersink.  What do you propose to do when the poor schmuck following your proposed "design", has this type of countersink?

https://www.grainger.com/product/21...kwcid=AL!2966!3!281698275570!!!g!472964099675!

How is he going to know what go/no-go gauge to use?

.. and I completely agree with you about the beauty of actually drafted prints.  Before the age of "click 'dimension it' in autocad" wizards, there was a lot of thought put into which dimensioning strategy was most helpful to the end user.  I lament the passing of this tradition.


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## William May (Aug 7, 2020)

If it is a production set-up, a go/no-go gauge would be set up for that inspection operation.  On aircraft, the inspectors had the gauges, and checked the holes to make sure they were in conformance with the print. They weren't expected to walk up, do a bunch of calculations, and then determine whether the hole met the specs. To do that with every hole would bring production to a halt. 
As far as your example of a countersink. I wouldn't even use the tool illustrated. It's not even a precision tool, since there is no reference point on it, to set it from.  It is for farmers and carpenters to make a countersink with.  That tool could not be used to produce a precision countersink without trial and error, which is no way to produce a quality part.  If you are going to take the time to do a set-up and test with that countersink, then take the setup down to drill the next hole, then set it up again and trial-test it again, you will soon learn why standardized tools exist.  You can do it, but it will be MUCH cheaper and faster to use a industry standard tool. That's why they exist.
If you can show me a standard production countersink with a pilot that varies from every other standard production countersink, I would like to see the shop using it. 
I have dozens of them, and they are all standard for their size and configuration. I can put the correct size countersink, in the correct spot, and know it will be right the first hole. 
You can do things a thousand different, harder, more arduous ways. But why would you do them that way? If you want output, you will work smarter,, not harder. 
The spec I gave you is still the easiest and fastest, and best to use.  It's the one that should be on the drawing. 
Again, making every viewer of the drawing do calculations should not be needed.  If calculation is needed, it should be done by the designer, not left to the worker to complete the drawing.


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## Richard Hed (Aug 8, 2020)

William May said:


> If it is a production set-up, a go/no-go gauge would be set up for that inspection operation.  On aircraft, the inspectors had the gauges, and checked the holes to make sure they were in conformance with the print. They weren't expected to walk up, do a bunch of calculations, and then determine whether the hole met the specs. To do that with every hole would bring production to a halt.
> As far as your example of a countersink. I wouldn't even use the tool illustrated. It's not even a precision tool, since there is no reference point on it, to set it from.  It is for farmers and carpenters to make a countersink with.  That tool could not be used to produce a precision countersink without trial and error, which is no way to produce a quality part.  If you are going to take the time to do a set-up and test with that countersink, then take the setup down to drill the next hole, then set it up again and trial-test it again, you will soon learn why standardized tools exist.  You can do it, but it will be MUCH cheaper and faster to use a industry standard tool. That's why they exist.
> If you can show me a standard production countersink with a pilot that varies from every other standard production countersink, I would like to see the shop using it.
> I have dozens of them, and they are all standard for their size and configuration. I can put the correct size countersink, in the correct spot, and know it will be right the first hole.
> ...


I am both a machinist and a draftsman (and I had some designing too) and I know as a machinist, that that last dim that the CADs will not allow, is one that as a machinist, I have to calculate out and write on the print I am using.  so where is all the crap about not allowing that last dim?  It is crap.  I'm not cheerleading for over dimming, not at all.  Just that when a machinist has to pencil in a dim, then that is something the CADs and drafters should have done.  So I agree with you, but often we mistake what others are trying to say.


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## William May (Aug 8, 2020)

Richard Hed said:


> I am both a machinist and a draftsman (and I had some designing too) and I know as a machinist, that that last dim that the CADs will not allow, is one that as a machinist, I have to calculate out and write on the print I am using.  so where is all the crap about not allowing that last dim?  It is crap.  I'm not cheerleading for over dimming, not at all.  Just that when a machinist has to pencil in a dim, then that is something the CADs and drafters should have done.  So I agree with you, but often we mistake what others are trying to say.


I don't know how CAD programs get away with eliminating that last digit, but I have seen it many times. It infuriates me that they replaced hand drawings with a computer system that is no able to fully replace a human.  I still hand draw all my drawings. I still use a drafting table. I still do all my own calculations.  Since I carry the papers out to my shop and make the parts, I am very particular about making sure the drawing is correct and carries the necessary info to produce the part. If I have to start doing calculations when I am machining, then I know I have failed.


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## Richard Hed (Aug 8, 2020)

William May said:


> I don't know how CAD programs get away with eliminating that last digit, but I have seen it many times. It infuriates me that they replaced hand drawings with a computer system that is no able to fully replace a human.  I still hand draw all my drawings. I still use a drafting table. I still do all my own calculations.  Since I carry the papers out to my shop and make the parts, I am very particular about making sure the drawing is correct and carries the necessary info to produce the part. If I have to start doing calculations when I am machining, then I know I have failed.


I used to do hand drawings and I taught drafting both manual and CAD.  Altho' manual is "fun" to do, it is quite slow and exacting.  CAD is quick and clean and it also stores nicely in computers and backup files quite nicely.  My problem is that the programmers of the various CADs have been instructed to have the computer NOT put in that last dim.  As a machinist, there are places that I might want a couple dims added up or subtracted and also put on the drawing, as I have to do that as a machinist and I have to mark my papers as such. and as a draftsman, particularly for MY OWN stuff, I should have the freedom to dim my stuff as I like without some con man in a suit in some other country or state, that I will never see (but I WILL cuss him), or some association of designers telling me how to dim when I want it MY WAY!  I am the one who buys the program--I am the customer and I am ALWAYS right.  I can say it over and over, and over and over again, If I have to make calculations and then write them on the drawing as "notes", then in my opinion the CAD should have a  toggle button to allow any dims I want.  I can put them in parens as some programs allow or another color, or in invisible ink that comes out when printed--I really don't care how it's done.  It's like microsux pushing us all around with the way THEY want US to do OUR computers!  Really cannot stand that.  I own my computer, I pay good money for microsux's OS, and I have a legitimate copy of a powerful CAD, and I don't want any aqzholio telling me in any way what I can do with MY computer that I paid good money for!  It's far worse than merely frustrating, it's the type of krap that someone like myself has a stroke over.  Calm down, calm down, here, have a nice espresso and relax.


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## William May (Aug 8, 2020)

Richard Hed said:


> I used to do hand drawings and I taught drafting both manual and CAD.  Altho' manual is "fun" to do, it is quite slow and exacting.  CAD is quick and clean and it also stores nicely in computers and backup files quite nicely.  My problem is that the programmers of the various CADs have been instructed to have the computer NOT put in that last dim.  As a machinist, there are places that I might want a couple dims added up or subtracted and also put on the drawing, as I have to do that as a machinist and I have to mark my papers as such. and as a draftsman, particularly for MY OWN stuff, I should have the freedom to dim my stuff as I like without some con man in a suit in some other country or state, that I will never see (but I WILL cuss him), or some association of designers telling me how to dim when I want it MY WAY!  I am the one who buys the program--I am the customer and I am ALWAYS right.  I can say it over and over, and over and over again, If I have to make calculations and then write them on the drawing as "notes", then in my opinion the CAD should have a  toggle button to allow any dims I want.  I can put them in parens as some programs allow or another color, or in invisible ink that comes out when printed--I really don't care how it's done.  It's like microsux pushing us all around with the way THEY want US to do OUR computers!  Really cannot stand that.  I own my computer, I pay good money for microsux's OS, and I have a legitimate copy of a powerful CAD, and I don't want any aqzholio telling me in any way what I can do with MY computer that I paid good money for!  It's far worse than merely frustrating, it's the type of krap that someone like myself has a stroke over.  Calm down, calm down, here, have a nice espresso and relax.


I feel your pain! I had to suffer from bad aviation drawings for the last 25 years. Before then, they were actually OK. When the computers took over, the guys who knew how to draw were replaced by tech school graduates who knew how to run a computer, but had no clue about how to present information on a drawing. 
(One of my prized drawings is from the German V-2 rocket program in WWII. It is an original blueprint, and I bought it at a garage sale in California. I assume the guy either worked on the V-2, or had some association with it, as most of the early rocket engineers in the U.S. were from Germany.  In any case, it is one of the most beautiful technical drawings I have ever seen. It even has the safety-wire for the bolts that attach the different sections together. (Only Germans would have safetied bolts on a device that had a total flight time of 15 minutes.) It is more like looking at a photograph than a drawing. Then I went to work for an U.S. aircraft manufacturer, and found out how badly they could mangle the simplest print.)


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## goldstar31 (Aug 8, 2020)

William May said:


> (One of my prized drawings is from the German V-2 rocket program in WWII. It is an original blueprint, and I bought it at a garage sale in California. I assume the guy either worked on the V-2, or had some association with it, as most of the early rocket engineers in the U.S. were from Germany.  In any case, it is one of the most beautiful technical drawings I have ever seen. It even has the safety-wire for the bolts that attach the different sections together. (Only Germans would have safetied bolts on a device that had a total flight time of 15 minutes.) It is more like looking at a photograph than a drawing. Then I went to work for an U.S. aircraft manufacturer, and found out how badly they could mangle the simplest print.)



William
               The odds are that it is a fake- and that it was deliberately done to attempt to fool- well , people who became our enemies. As such I would regard it as a treasure to keep and simply wonder---if?????

it's the sort of thing that British Intelligence kept observing a new German Airfield
 with with Dummy planes and buildings and all sorts of things.  Once the construction was finished , the Royal Air Force was ordered to bomb it------with WOODEN Boombs

Half the success in politics is miss-information.  

Cheers

Norman


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## Richard Hed (Aug 8, 2020)

William May said:


> I feel your pain! I had to suffer from bad aviation drawings for the last 25 years. Before then, they were actually OK. When the computers took over, the guys who knew how to draw were replaced by tech school graduates who knew how to run a computer, but had no clue about how to present information on a drawing.
> (One of my prized drawings is from the German V-2 rocket program in WWII. It is an original blueprint, and I bought it at a garage sale in California. I assume the guy either worked on the V-2, or had some association with it, as most of the early rocket engineers in the U.S. were from Germany.  In any case, it is one of the most beautiful technical drawings I have ever seen. It even has the safety-wire for the bolts that attach the different sections together. (Only Germans would have safetied bolts on a device that had a total flight time of 15 minutes.) It is more like looking at a photograph than a drawing. Then I went to work for an U.S. aircraft manufacturer, and found out how badly they could mangle the simplest print.)


wood u consider taking a photo of it an showing us?  I'd be interested in seeing it.  I thimks that the new drafting techs have had no experience in real life and are just pushing around a mouse, clikking buttons, never having had any experience in the shops or manufacturing environments.


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## willray (Aug 8, 2020)

William May said:


> If it is a production set-up, a go/no-go gauge would be set up for that inspection operation.



I'll stop flogging the dead horse after this, but -- how would a go/no-go gauge be set up for that operation, based on your proposed "specification" for that feature, which provides an instruction for creating the feature, but no specification for its dimensions?

hint - following your "specification", you will produce a feature that is not .225 in diameter.  I think it's reasonable to assume that the design intent, is a feature .225 in diameter, as that is the specification that the designer provided.  How will you arrive at that design intent, to create a go/no-go gauge for the feature, from your instruction?

As an aside, since one must do exactly the same math (with the application of some additional assumptions) to derive the actual design intent from your "specification" so that the feature can actually be checked, why do you think that providing the instruction, rather than the feature specification, is somehow advantageous?



> On aircraft, the inspectors had the gauges, and checked the holes to make sure they were in conformance with the print.



What exactly does conformance with "82 degree countersink, .129 deep" mean?   It is not a specification to which there can be conformance or non-conformance.  It's an instruction.  How do your inspectors know which gauges to use, if the feature specification is not on the print?



> As far as your example of a countersink. I wouldn't even use the tool illustrated. It's not even a precision tool, since there is no reference point on it, to set it from.  It is for farmers and carpenters to make a countersink with.  That tool could not be used to produce a precision countersink without trial and error, which is no way to produce a quality part.  If you are going to take the time to do a set-up and test with that countersink, then take the setup down to drill the next hole, then set it up again and trial-test it again, you will soon learn why standardized tools exist.  You can do it, but it will be MUCH cheaper and faster to use a industry standard tool. That's why they exist.
> If you can show me a standard production countersink with a pilot that varies from every other standard production countersink, I would like to see the shop using it.
> I have dozens of them, and they are all standard for their size and configuration. I can put the correct size countersink, in the correct spot, and know it will be right the first hole.



My apologies, that was just the immediate first one of the designs that illustrated the problem with providing instructions rather than specifications in a print, that came up in a quick search.  Many zero-flute countersinks in larger sizes have blunt tips.  Many countersinks for larger bores use indexable inserts and have blunt noses.  Thru-coolant countersinks don't have a nose at all.  If you're not familiar with them, you should really look at what large-scale production uses.

Your proposed "specification" provides an instruction for creating a feature, with one particular method, with one particular tool, and it makes assumptions about the tool.  That is an instruction.  A specification should provide the important details of the feature, so that a machinist using any method, and any tool, can produce that feature, and so that the correctness of that feature on a machined part can be determined.  The specification should not need to be reverse-engineered from the instruction, by application of assumptions about the process and tooling.


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## William May (Aug 8, 2020)

goldstar31 said:


> William
> The odds are that it is a fake- and that it was deliberately done to attempt to fool- well , people who became our enemies. As such I would regard it as a treasure to keep and simply wonder---if?????
> 
> it's the sort of thing that British Intelligence kept observing a new German Airfield
> ...


Well, I don't see anything that would make it a fake.  This particular print deals with the body joints on the V-2, from the nose cone down to the rear body joint with the engine attach. I have looked at real V-2's at both the Smithsonian and places like the White Sands Missile Museum, and everywhere else I could see one, and all the details are as described. I have never  been able to see the joint that has the safety-wire on it on a real one, but that would be the only difference that I can see that would be missing. The one at White Sands is only the lower engine section, and it was outside, and I could freely look at all the attachment points, and they all matched the drawings. I don't think the Germans were faking blueprints. since no one would have access to them if they did not work on the program. 
Vast amounts of blueprints were gathered during operation "Paperclip", when the U.S. basically took everything that wasn't nailed down. They handed out literally TONS of information to any U.S. company that asked for it. One of Germany's largest supersonic wind-tunnels went to Bell Aircraft. It was stumbled upon by Major Larry Bell, ummmm......who owned Bell Aircraft.  He also loaded up the Messerschmitt prototype P-1061 and all the drawings. 
(Google the Bell X-5 and you will get the story on THAT episode)  
Howard Hughes asked for, and got, an Me 262 aircraft. He not only wanted to fly it to see what it was like, he wanted to enter it in the 1946 Thompson Trophy Races, in the unlimited category. (He didn't mention THAT part when he requested the aircraft!) Since the Me-262 was still superior to any aircraft the U.S. had at that time, the government said that there was NO WAY a Nazi aircraft was going to win an American race, and he was refused entry. The reason I know this, is that one of the guys who worked on it to bring it back to flying condition was one of my A&P instructors in aircraft maintenance when I was working on getting my mechanic's license out of high school. He did a lot of work on the Jumo engines, and reported them as very troublesome. The fuel controls had to be set EVERY DAY with the current barometric settings to make them operate correctly for that day. Hughes got the aircraft, along with 15 Jumo engines as spares. They went through that aircraft and by the time it was done, it was in better-than-new condition.  The after restoration photos are in several books on the Me-262. When you look at the pics, you can see it is ready to race.  When he was stymied in that race effort, he donated the aircraft to a mechanic's school in Claremont, California. When that school closed, the aircraft was bought by Ed Maloney, at the "Planes of Fame" museum in Ontario, California. It has since been sold to Paul Allen, who buys WWII aircraft and restores them to original flying condition.  He has since died, and I have not heard anything more about the aircraft. 
I learned to keep my eyes open when going to garage sales in Los Angeles. You literally NEVER knew what you were going to see and be able to buy. Just as now, when gramps died, everything went to a yard sale, and what didn't sell, went in the trash.  Back in the 1970's, when I lived there, the yellow pages phone book was 15 inches high, and came in about 8 separate books. I think it was the only city in the world where you could look up "Rocket Nozzle Coatings" in the phone book, and come up with 5 different businesses.  The aerospace industry in California at the time was Stupendous.  There were aircraft and space related factories in nearly every large California town.  I would say that the number of engineers there working in aerospace must have numbered in the hundreds of thousands, if not in the millions.  There is no doubt it is a genuine blueprint. (Not an original, but a shop floor blueprint that some engineer kept as a souvenir.)  I wound up with 4 blueprints in a folder, for 25 cents.  I collected all the stuff I could afford to purchase on what I made, working at a gas station. I also came across a complete set of factory blueprints for the Curtiss Pusher. A lot of people said that Curtiss never worked to blueprints, they just did chalk drawings on a wall. I know that is not true, because I have a set of the originals. 
If I can take a picture of the V-2 print, I will put it on here.


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## William May (Aug 8, 2020)

willray said:


> I'll stop flogging the dead horse after this, but -- how would a go/no-go gauge be set up for that operation, based on your proposed "specification" for that feature, which provides an instruction for creating the feature, but no specification for its dimensions?
> 
> hint - following your "specification", you will produce a feature that is not .225 in diameter.  I think it's reasonable to assume that the design intent, is a feature .225 in diameter, as that is the specification that the designer provided.  How will you arrive at that design intent, to create a go/no-go gauge for the feature, from your instruction?
> 
> ...


Well, you put what you want on your drawings, and I will put what I want on mine. 
Again, if the first thing they have to do when they get your print is get out a calculator and figure out what you REALLY wanted, then the print is no good. I am sorry if you are offended by this, but it is reality.  I have worked in aviation for 42 years, and I know the difference between a good print and a bad one. You are just conditioned to skip stuff by calling it an "instruction" rather than a "specification"
EVERY drawing is an INSTRUCTION into how a part is to be made.  That is what a drawing is.  One of my instructors once told me about the American Indian's puzzlement over Cavalry written orders. They could not comprehend how a piece of paper could convey "What is in another man's mind" without actually talking to that person.  
But the point was that you need to make your drawings clear enough so that ANYONE can see and understand "What is in another man's mind"
And that is where I will let the matter rest.


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## Richard Hed (Aug 8, 2020)

William May said:


> Well, you put what you want on your drawings, and I will put what I want on mine.
> Again, if the first thing they have to do when they get your print is get out a calculator and figure out what you REALLY wanted, then the print is no good. I am sorry if you are offended by this, but it is reality.  I have worked in aviation for 42 years, and I know the difference between a good print and a bad one. You are just conditioned to skip stuff by calling it an "instruction" rather than a "specification"
> EVERY drawing is an INSTRUCTION into how a part is to be made.  That is what a drawing is.  One of my instructors once told me about the American Indian's puzzlement over Cavalry written orders. They could not comprehend how a piece of paper could convey "What is in another man's mind" without actually talking to that person.
> But the point was that you need to make your drawings clear enough so that ANYONE can see and understand "What is in another man's mind"
> And that is where I will let the matter rest.


As far as I know, a "specification" is something that is required by the engineers.  But there are other things that matter to a machinist (and please remember, dear reader, that WE HERE are all AMATEUR model makers even if we are professionals) that might be called instructions or "over-dims" or "notes" or whatever which tell the machinist how to proceed.  Often, those instructions are in the notes but some CAD programs allow an over-dim in parens.  I prefer the paren method -- it's quick, it's easy, it's clear, it's precise.


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## Richard Hed (Aug 8, 2020)

willray said:


> Ok, I'll soften my "completely useless" assessment. I hadn't thought of touching off on the diameter of the hole with a centered countersink, and then plunging the additional 0.0627.  That certainly gets you where you need to be as well.
> 
> If I were dimensioning a drawing imagining that the machinist might take that approach, I would have provided the 82 degree countersink, and the 0.0627 additional plunge depth, rather than the .225 diameter.


Will:, I keep laughing at that number:  .0627--That number would not even be used in rocket science, as far as I know.  there is no reason to use four places for a screw in amateur usage!  for us Amateurs, .06 (1/16th") is just fine.  the difference is less than the thickness of paper and about the thickness of fine hair.  I say "fine" hair for a reason:  not all hair is the same thickness!  1/16th is .0625.  so the diff between .0627 and .0625 (1/16th) is two ten-thousandths!  Add up the weight on that difference for 100,000 holes, say in a Boeing jet, and it won't change any parameters or be enough to make the plane crash or disintegrate.   It won't weigh any significant amount.

I doubt that any mill available for amateurs (costing less than 100,000$) would even have capability coming close to a half thou.


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## awake (Aug 8, 2020)

We got into some of this in an earlier discussion, and again I am wondering if we are mixing up dimensions that _define_ the part, vs. dimensions that _describe_ it. Probably not the right terminology, but it makes sense for a CAD program not to let you over-constrain a drawing (defining it). Once you have given it every dimension that fully constrains the part, adding another just becomes a source of error.

BUT! When you produce prints of the part, the CAD program SHOULD allow you to indicate the dimensions of any and all features (describing it), regardless of whether or not that dimension is required for constraining or would constitute over-constraining. From our previous discussion, it sounds like there are CAD programs that don't allow this ... maybe time to change programs! (Yeah, I know - hard to lose all the time invested in learning how to use the current program.)


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## Richard Hed (Aug 8, 2020)

awake said:


> We got into some of this in an earlier discussion, and again I am wondering if we are mixing up dimensions that _define_ the part, vs. dimensions that _describe_ it. Probably not the right terminology, but it makes sense for a CAD program not to let you over-constrain a drawing (defining it). Once you have given it every dimension that fully constrains the part, adding another just becomes a source of error.
> 
> BUT! When you produce prints of the part, the CAD program SHOULD allow you to indicate the dimensions of any and all features (describing it), regardless of whether or not that dimension is required for constraining or would constitute over-constraining. From our previous discussion, it sounds like there are CAD programs that don't allow this ... maybe time to change programs! (Yeah, I know - hard to lose all the time invested in learning how to use the current program.)


Yes, yes, this is correct.  What you are calling "define" is called "specs" or specifications by the pros.  These are requirements.  What you call "describing" is either notes or instructions.  Yes, you are so correct.  The problem is that in a CAD drawing, the number of dims is related to the "constraints" which conflicts with what a machinist has to do.  so now I am concluding that PART of a machinists job is to sit up and read all the notes (well known practice), and make his/her own notes and pencilled in dims right on the drawing he/she is given.  I thimk that CADs should be modified so that the drafter can place non-required dims into the drawing, maybe in greyed colors/lines so one cannot mistake it for a requirement.


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## Asm109 (Aug 8, 2020)

Let me give a real world example that I dealt with just last week.
I am designing a short tube that holds and locates a lens.
Tube has a through hole and a counterbored hole from one end.
The lens drops into the counter bored hole.  What is most critical to me is the distance from the bottom of the hole to the face of the part at the end of the through hole.  Overall length is not critical, depth of counter bore is a big fat don't care.  The length of the through hole needs to be +- .001".
So I dimensioned that feature explicitly, I dimension the overall with a moderate tolerance.    Now I know that a machinist would like to bore the counterbore and control that depth in one op but to meet MY REQUIREMENTS, he would have to control BOTH the Overall length AND the depth of counterbore to a total variation of less than +-.001.  What is important is that the drawing clearly shows what is needed to be a functional part. How it is made is up to the machinists.


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## easymike29 (Aug 8, 2020)

The OP's image clearly describes the countersink requirements according to drafting standards. I don't know what the fuss is all about.

Eugne


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## haakonpe (Aug 8, 2020)

Essential right angle trig formula:
the Tangent of an angle is  = the length of the leg Opposite of the angle measured divided by the length of the leg adjacent to the angle
Tan = Op/Adj

Given:
Tan 41= .8693
adj = .1125

We can re-write it as:
.8693=.1125/Adj  
or... 
Adj * .8693 = .1125
so...
Adj = .1125/.8693
Adj = .1294

adj represents the total depth from the surface of the material (to Bill's point touch off with shim and compensate)
adj will be .1294 down from the surface.  If you want to compensate from touching off inside the whole, run the calc again with the adj being .058 (half the diameter of the hole) and subtract that from the total distance to get the additional distance needed.

Here's a quick on line calculator for the visuals:
Trigonometry Calculator. Simple way to find sin, cos, tan, cot 

Pete


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## Richard Hed (Aug 8, 2020)

Asm109 said:


> Let me give a real world example that I dealt with just last week.
> I am designing a short tube that holds and locates a lens.
> Tube has a through hole and a counterbored hole from one end.
> The lens drops into the counter bored hole.  What is most critical to me is the distance from the bottom of the hole to the face of the part at the end of the through hole.  Overall length is not critical, depth of counter bore is a big fat don't care.  The length of the through hole needs to be +- .001".
> So I dimensioned that feature explicitly, I dimension the overall with a moderate tolerance.    Now I know that a machinist would like to bore the counterbore and control that depth in one op but to meet MY REQUIREMENTS, he would have to control BOTH the Overall length AND the depth of counterbore to a total variation of less than +-.001.  What is important is that the drawing clearly shows what is needed to be a functional part. How it is made is up to the machinists.


Your requirments should be easy to meet with a good lathe and other quality tools.  What is the material?  How large of a lens?  I do telescopes--not lenses but mirrors.  I might be interested later in 6" lens or smaller eye-lenses (hmmm, correct word escapes me but for focusing.)


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## Asm109 (Aug 8, 2020)

7075 T6  lens diameter is .5 inches.
Oh I know my needs are able to be met,  the point was the drawing needs to specify what's needed, not the simplest way to make the part.


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## Richard Hed (Aug 8, 2020)

Asm109 said:


> Let me give a real world example that I dealt with just last week.
> I am designing a short tube that holds and locates a lens.
> Tube has a through hole and a counterbored hole from one end.
> The lens drops into the counter bored hole.  What is most critical to me is the distance from the bottom of the hole to the face of the part at the end of the through hole.  Overall length is not critical, depth of counter bore is a big fat don't care.  The length of the through hole needs to be +- .001".
> So I dimensioned that feature explicitly, I dimension the overall with a moderate tolerance.    Now I know that a machinist would like to bore the counterbore and control that depth in one op but to meet MY REQUIREMENTS, he would have to control BOTH the Overall length AND the depth of counterbore to a total variation of less than +-.001.  What is important is that the drawing clearly shows what is needed to be a functional part. How it is made is up to the machinists.


Do you make the lenses too, or just the holder?  Due to the high cost of focussing lenses, I thimk I eventually will try my hand at that.


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## Asm109 (Aug 9, 2020)

No I don't make lenses,  I get paid to do what I am good at. Design optical mounting systems.  My company pays other companies who are good at making lenses to do so.


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## goldstar31 (Aug 9, 2020)

But gentlemen MOST if not all of the erudite conversation is from full size operations and NOT from what most of us have in our own badly funded home workshops where   either a badly in need of replacing our repair of an ancient lathe or mill or perhaps some badly equipped Chinese little misery is the norm.

The place seems dotted with repeated and repeated  questions- and sometimes doubtful answers about the actual problems which beset most of us.

Here it suggests some impossible dream removed from ever becoming reality- at least for me.

Perhaps someone else might dare to agree with me?

I should perhaps explain that there is a precedent  in the past where I recall contributors talking about thousands of an inch and only possessing rulers and lathes without dials and TPI which would only produce 62.5 gradations per revolution.

I feel sorry for those  who are trying hard in solving the problems of their own little world of making models and things to go with them.


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## Misterg (Aug 9, 2020)

Richard Hed said:


> I thimk that CADs should be modified so that the drafter can place non-required dims into the drawing, maybe in greyed colors/lines so one cannot mistake it for a requirement.



I doubt that anything needs modifying - this is the exact purpose of "Reference Dimensions" - they appear in brackets on prints (or with the suffix 'REF' depending on drawing standards). I can't speak for all CAD programs, but both Creo and Fusion360 allow them.


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## goldstar31 (Aug 9, 2020)

Well Igot one response from an a young-ish correspondent who cou;d do with a bit of my experience on a somewhat ancient- well younger than me- lathe. 

Thanks Jon being told in real terms that there IS a real world out there. 

Oddly, I've just received a fancy DRO to fit on my Myford.  Laughingly, it would look quite amusing on a 7 by ? Chinese lathe


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## nealeb (Aug 9, 2020)

As an amateur (mechanical) engineer and enthusiastic 3D CAD (F360) user, I have been finding this debate interesting, amusing, and occasionally instructive by turns!

I have given a number of 3D CAD tutorial sessions to fellow club members, and I have to say that it is a lot easier to teach people with no knowledge of CAD than those with many years of experience of 2D draughting. The reason is partly tied into some of points of view expressed here. 

I bang on to my "pupils" the need for a3D model to express "design intent" and not embody good 2D engineering drawing practice. In the case of the countersink, what is going through the designer's mind is, "what is the minimum depth of the countersink so that allowing for bolt manufacturing tolerance, the head will be at least, say, 10thou below the surface." In my hypothetical 3D model, this is what I would construct. Everything else follows on from that. Now, some time downstream, the designer has to produce engineering drawings to go to the workshop. I know that in F360, these can have as many dimensions as you wish, whether the drawing is over-dimensioned or not. These dimensions (to whatever number of decimal places you as designer choose) will never disagree because they all derive from the original 3D model (and if that model is updated, the dimensions will automatically be recalculated). The question is, though, to what extent the designer should define or assume the  details of the manufacturing process and thereby choose what dimensions to put on the drawing? Should he know what the point of the countersink is? Sharp, 20thou, 40thou, flat? How will the machinist set his machine? Will he end up with a machinist banging on his desk and saying that he doesn't want to be told how to do the job? So, he might just translate the initial design intent into external diameter of the countersink and let the machining experts work out how to achieve that. With a simple bit of trig, perhaps? Maybe there is a production engineering stage between designer and machinist who makes these decisions, and might even ask for specific relevant dimensions on the drawings to suit the local ways of working.

As for inspection - design intent could be checked with a simple gauge that looks like a dummy bolt made to max tolerance conditions of the bolts to be used. Does it sit 10thou below the surface? Do the drawing dimensions required by the inspection department have anything to do with the dimensions needed to manufacture the piece? Quite possibly not. Should just one drawing have all the dimensions required by both parties, even though they might over-complicate and confuse things? Should there be two drawings derived from the same model (ensuring consistency) aimed at the specific user?

I know from my own experience that as designer and machinist, what I put in the model for design purposes is not what I want for the machining process. Great thing about 3D CAD is that it separates the two, while guaranteeing consistency (although I look forward to the F360 version that will update my scruffy and oil-stained drawing prints hanging over the lathe as soon as I update the computer 3D model!)


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## cds4byu (Aug 9, 2020)

ISO has a specification for the dimensions and the dimensioning practice for countersunk screws.  ISO 15065.

The CAD systems I work with automatically create both the numerical dimensions and the dimensioning practice in conformance with the standards.

Carl


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## Richard Carlstedt (Aug 9, 2020)

Nealeb, your quote in post 64
" Maybe there is a production engineering stage between designer and machinist who makes these decisions, and might even ask for specific relevant dimensions on the drawings to suit the local ways of working "
is spot on !

 I am a retired Manufacturing Engineer
Not all companies use this resource for making a product. Several firms I worked for believed in Mfg Eng.
At one Die Maker Company I worked for, they were pulling their hair out due to errors and hired me. After a year there, I showed the owners that 82 % of the drawings/specifications had errors. So in essence I had to "redline" all those CAD  drawings so the machinists could make the parts that would fit other parts. I am proficient in Solidworks and know that many "adaptations" can be made to prints, but designers either have no knowledge of manufacturing steps, do not know their CAD system, will not accept changes , resort to standard protocol like ISO or whatever , and therefore make it difficult to manufacture .  Now stop ! There is one area that is near impossible to  get corrected....a  "Customers" drawing... When you have those, all bets are off . But for your own shop or company, there is no reason a "note" cannot be provided spelling out the objective of a dimension.  Last note, ALL CAD users are taught to never duplicate dimensions...Why ?  That rule is dumb. First, that "concept" is a holdover from Manual drawings because it could produce errors. In a CAD system (3D) where a model has been created. It is impossible to have two different dimensions for the same measurement. . It can save minutes/hours on a print with many dimensions so the machinist does not have to search for it. 
This discussion is  a huge subject so I will stop here
Rich


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## willray (Aug 9, 2020)

Richard Hed said:


> Will:, I keep laughing at that number:  .0627--That number would not even be used in rocket science, as far as I know.  there is no reason to use four places for a screw in amateur usage!  for us Amateurs, .06 (1/16th") is just fine.  the difference is less than the thickness of paper and about the thickness of fine hair.  I say "fine" hair for a reason:  not all hair is the same thickness!  1/16th is .0625.  so the diff between .0627 and .0625 (1/16th) is two ten-thousandths!  Add up the weight on that difference for 100,000 holes, say in a Boeing jet, and it won't change any parameters or be enough to make the plane crash or disintegrate.   It won't weigh any significant amount.



Richard, I was just quoting the figure being discussed in a previous post.  However, I would suggest, if you're going to make "eh, close enough" approximations for an alternative dimensioning strategy to the "82 deg at .225 diameter" specification, that it would be wiser to choose .063 depth of the countersink as the simplification.  1/16 is a nice fraction, but since few of our machines speak to us in fractions, it's not really much friendlier at the handwheels than .0627.  Given the limits of our typical dials, we're stuck with .062 or .063, and since we don't know how much wiggle-room the original designer left us in the .225 dia. spec to prevent the screw head from being proud of the surface, shorting the depth by aiming at .062 (or less) in a redimension seems unwise.


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## willray (Aug 9, 2020)

Richard Carlstedt said:


> In a CAD system (3D) where a model has been created. It is impossible to have two different dimensions for the same measurement.



Sadly, no, it is not impossible - or at least not impossible for a feature to have two different dimensions "in the drawing" depending on which dimensions you add/follow to arrive at the feature's specification.  And this is why it remains important to not over-dimension parts.

If you would like an example, simply draft yourself up a right triangle with both legs of length 1 in your CAD program and dimension both legs and the hypotenuse, as well as the angles.  Unless your CAD program represents the length of the hypotenuse as sqrt(2), you now have a drawing where /some/ dimension on the drawing, must be false.  If you provide that drawing as a specification, the end-user must make assumptions regarding which dimension(s) are to be ignored.

With a right triangle, one might believe that any reasonable machinist would assume that the right angle, and legs are the defining dimensions, and that the hypotenuse and 45-degree angles should simply be allowed to fall where they will.  With drawings that are more complex however, over dimensioning rapidly makes it impossible to figure out which dimensions are actually the intended specification.


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## nealeb (Aug 10, 2020)

And that is why, particularly when using 3D CAD, you have to differentiate between "design intent" as built into the model, and the engineering drawings that are produced from it. In the days of manual 2D draughting, this difference didn't really exist as there was only ever going to be the one drawing, with its views and sections and so on (and a lot of mental effort by the draughtsman/designer to ensure that these were all consistent). In the example from the previous post, my model would be fully defined by two sides and the right-angle between them. In F360, if I tried to put a dimension (at the model-building stage) on the hypotenuse it would quite rightly tell me that it was over-specifying. In fact, it would add the calculated dimension but put it in parentheses as a flag. However, when I come to produce engineering drawings from the same model I can select any combination of sides and angles to dimension because these are derived from the model. I would choose whichever best suited the downstream process - in my case, what I needed to make the part in my workshop!


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## willray (Aug 10, 2020)

nealeb said:


> However, when I come to produce engineering drawings from the same model I can select any combination of sides and angles to dimension because these are derived from the model. I would choose whichever best suited the downstream process - in my case, what I needed to make the part in my workshop!



Actually, it can be a bit worse than that.  You need to understand and choose appropriately so that you don't lose the design intent, when making choices about which dimensions to carry through to your production process.  With the right-triangle example, if you choose to carry the hypotenuse and the two 45 degree corners down to your (let's call them) "shop drawings", and you faithfully produce parts to that drawing, your triangles will _not_ have 1-inch long sides, and you will have failed to produce parts that meet the design intent.

This is a bit of a contrived example (though completely real, and it's terribly easy to land in this situation in a less-contrived drawings as soon as you have anything other than parallel or perpendicular features), but, given this drawing, a) how long is the block, b) what is the angle the sloped section makes with the horizontal, and c) if you, and two other machinists independently choose subsets of those dimensions to carry down to your "shop drawings", how likely is it, do you think, that you will all produce parts that are identical?







(This doesn't even /have/ derived dimensions - all of those are true dimensions, to the precision at which I'm working.  And yet, even without derived dimensions it's still confusing as !#@$, because it was dimensioned by a lazy person who didn't think about conveying the design intent.  Derived dimensions that are not clearly understood as derived, _or_ not clearly understood as to _how_ they were derived, make hash of understanding the design intent even more quickly.  This is part of the reason why it's often important to leave the job of deriving the dimensions to the machinist, or process-design engineer - then they understand _how_ the derived dimensions were arrived at).

Overdimensioning is a curse.  I quite like _derived_ dimensions (when they are represented as derived), but overdimensioning, when it's not obvious which are the derived dimensions, ablates the downstream user's ability to understand the design intent.  "Shop drawings" that omit design dimensions in favor of "more relevant to the machining process" derived dimensions, make it impossible to determine whether the thing you're making, meets the design specifications.  "Instructions", as proposed by William Mays, when they are produced with a knowledge of the design specifications, are wonderful, but they can rarely be used to check compliance with the design spec.

I really don't want to call the hue and cry for "gimme all the dimensions" a product of laziness, but a good designer or draftsman puts considerable effort into choosing the appropriate dimensions to represent, so that the design intent is properly conveyed.  Studying those choices, and arriving at an understanding of the design intent, is part of what should be the machinist's job, and should be part of the treasured skill set that sets the machinist apart from the ape.

I would never argue that that job should be made harder by the provision of badly-dimensioned drawings, and lord knows CAD programs produce some awfully lazy "draftspersons" and badly-dimensioned drawings.  However, this job or hobby should not be "Oooh - Numbers!  Grugg turn dials now!".


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## Richard Hed (Aug 10, 2020)

willray said:


> Richard, I was just quoting the figure being discussed in a previous post.  However, I would suggest, if you're going to make "eh, close enough" approximations for an alternative dimensioning strategy to the "82 deg at .225 diameter" specification, that it would be wiser to choose .063 depth of the countersink as the simplification.  1/16 is a nice fraction, but since few of our machines speak to us in fractions, it's not really much friendlier at the handwheels than .0627.  Given the limits of our typical dials, we're stuck with .062 or .063, and since we don't know how much wiggle-room the original designer left us in the .225 dia. spec to prevent the screw head from being proud of the surface, shorting the depth by aiming at .062 (or less) in a redimension seems unwise.


Of course.


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## Richard Hed (Aug 10, 2020)

willray said:


> Sadly, no, it is not impossible - or at least not impossible for a feature to have two different dimensions "in the drawing" depending on which dimensions you add/follow to arrive at the feature's specification.  And this is why it remains important to not over-dimension parts.
> 
> If you would like an example, simply draft yourself up a right triangle with both legs of length 1 in your CAD program and dimension both legs and the hypotenuse, as well as the angles.  Unless your CAD program represents the length of the hypotenuse as sqrt(2), you now have a drawing where /some/ dimension on the drawing, must be false.  If you provide that drawing as a specification, the end-user must make assumptions regarding which dimension(s) are to be ignored.
> 
> With a right triangle, one might believe that any reasonable machinist would assume that the right angle, and legs are the defining dimensions, and that the hypotenuse and 45-degree angles should simply be allowed to fall where they will.  With drawings that are more complex however, over dimensioning rapidly makes it impossible to figure out which dimensions are actually the intended specification.


Yes, you are correct.  I was not clear on what I meant.  What I am thimking is that, say you have a part 4 units long but it is broken up into 3 or 4 sections like two bearings on the ends, a larger section then a larger yet section.  As a machinist I might need to pencil in two dims that I wish to know over and above the printed dims.  like from the left end to the end of the third section which has already been dimmed properly but sometimes it is necessary for other dims than the proper ones.  and as for myself, I would prefer to have a toggle system in my CADs to turn on or off such a capability.  For other peeps, of course, like work drawings for sale or whatever, you wouldn't do such a thing.  It's only for my own convenience that I don't have to use a calculator to pencil them in--let the CAD do the work.  Most of all, I really do not like machines (or even people) telling me how to make something or what to do or not to do.  I take instruction and advice nicely but NOT orders.


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## willray (Aug 10, 2020)

Richard Hed said:


> Yes, you are correct.  I was not clear on what I meant.  What I am thimking is that, say you have a part 4 units long but it is broken up into 3 or 4 sections like two bearings on the ends, a larger section then a larger yet section.  As a machinist I might need to pencil in two dims that I wish to know over and above the printed dims...



Hi Richard.  Mostly, I was railing against the suggestion that "Don't overdimension a drawing is a useless holdover from the days of manual drafting", and that since "computers don't make drafting errors", this convention was now irrelevant.   I'm sure you are already familiar with the issues, but there are so many self-taught/only-ever-driven CAD jockeys that think that this is true, that I believe this bears being explicit about.

While computers can be reasonably argued to make far fewer simple math errors than human draftspersons, the prohibition against overdimensioning was only ever peripherally about _mistakes_.

It was (and is) much more about preventing the possibility of a feature being able to be interpreted as located at more than one location, or having more than one dimension, with the difference depending on the path one takes through the provided dimensions.  Even without mistakes, this can easily happen due to "invisible digits" that can creep into dimensions, most obviously as a result of trig relationships defining the position of features.  The good designer or draftsperson makes sure that only those dimensions that allow the machinist to correctly position or dimension the part, are represented on the specification drawing.

Now, the wonder of the enabling technology of the computer doing the math for me to calculate derived dimensions to help me work through my machining strategy without needing to spend hours with a calculator, or a designer providing process hints like William May's "plunge your countersink .063 inches", those kinds of benefits I'll take any day of the week.  I just wish more of today's designers and CAD jockeys understood that just because "the computer doesn't make math errors", doesn't suddenly make overdimensioning ok, or reduce the amount of thought that the designer needs to put into choosing how to dimension the features to correctly communicate the design intent!


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## IanN (Aug 13, 2020)

easymike29 said:


> The OP's image clearly describes the countersink requirements according to drafting standards. I don't know what the fuss is all about.
> 
> Eugne



Hi Eugne,

I think you are missing the point - the criticism of the drawing is not whether it is correctly drawn, but is from people complaining that international drawing standards are wrong and that their personal way of doing things is right

Having worked in engineering for over 40 years I have come to hold such standards with great respect (I have seen the time, effort, consultation, consideration and debate that goes in to the process of defining them)


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## IanN (Aug 13, 2020)

goldstar31 said:


> But gentlemen MOST if not all of the erudite conversation is from full size operations and NOT from what most of us have in our own badly funded home workshops where   either a badly in need of replacing our repair of an ancient lathe or mill or perhaps some badly equipped Chinese little misery is the norm.
> :
> :
> in the past where I recall contributors talking about thousands of an inch and only possessing rulers and lathes without dials and TPI which would only produce 62.5 gradations per revolution.
> ...



Hi Norman,

Please don’t confuse the issue by dragging “reality” and common sense in to the debate

My first two steam engines were to designs by LBSC and dimensional tolerances were defined in instructions to turn a part to “1/8 inch bare” or “1/8 inch full”

Ian


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## goldstar31 (Aug 13, 2020)

IanN said:


> Hi Norman,
> 
> Please don’t confuse the issue by dragging “reality” and common sense in to the debate
> 
> ...



I was brought up in the. days when a blacksmith farrier had two pockets sewn into his fustians. One was for his best brass folding ruler and the other was one was worn with rounded ends from years of 'marking off' on metal. The rougher metal was marked off with regulation French chalk stick---- and it all worked.
It all worked as it did for his father before him in Shildon Works.

As for  'bare' and 'full', I never quite understood what LBSC was blethering about.  I suppose it was some strange Masonic symbolism that despite being a Provincial officer, I have yet to be 'introduced'

We come to the seemingly forgotten part of our hobby and some seem to have forgotten that we don not work in a factory where some geyser llike me came around taking samples to see that the machines are endlessly producing stuff that lies within the 3 Standard Deviations of the Accepted Mean- or NOT!

We are making a one off which will hopefully fit or rattles.  Surprisingly, it seems that a full size steam locomotive works best- when it rattles.

Probably, I'm missing those days when  the designs were sketched out in the soil of the blacksmith's shop----------- and everything worked.

So you you have the practical experiences of a 90 year old whose IQ is certainly not lying - one the Mean but seems to have wondered off to 135------and seems to have worked enough not to be an engineer but to have successfully retired - for longer than I have ever worked.

I suppose that this is a test which few dare take

My thoughts, of course

Norman


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## Richard Hed (Aug 13, 2020)

willray said:


> Hi Richard.  Mostly, I was railing against the suggestion that "Don't overdimension a drawing is a useless holdover from the days of manual drafting", and that since "computers don't make drafting errors", this convention was now irrelevant.   I'm sure you are already familiar with the issues, but there are so many self-taught/only-ever-driven CAD jockeys that think that this is true, that I believe this bears being explicit about.
> 
> While computers can be reasonably argued to make far fewer simple math errors than human draftspersons, the prohibition against overdimensioning was only ever peripherally about _mistakes_.
> 
> ...


Oh, yes, I agree.  I thimk maybe that the "associations" who make those conventions should reconsider some things (maybe they already have and I just doesn't know it)--those things are not the dimensions themselves but rather a method to point out where the first datum point is, for instance, labeling it "A" (or what ever) and if there is a second datum to label it "B" and so on.  There certainly are some symbols that could be used like this.  Maybe already done and I just doesn't know it.


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## easymike29 (Aug 13, 2020)

I mean no disrespect to any reader of this thread especially of the OP, but any of my apprentices could tell you  the depth of that countersink. Most of them could derive it without picking up a pencil, just their calculator.  The others would be able to sketch it out and then do the math. No muss, no fuss, no whining. They also would know that it only is of value as an approximation of how deep to plunge the countersink. He/she would only be concerned with thru hole size, countersink degrees and .225 Diameter at the opening. That's not all they were able to accomplish but what they did learn made them more valuable to a future employer. Don't underestimate what a competent machinist is capable of doing. Just create a properly toleranced object and don't be concerned about how he/she proceeds. 
Please, readers, I am not posting this to offend anyone. If machining is just your hobby you can't or shouldn't  be expected to have the knowledge of one that does it for a living.
The OP has asked for us to share some of that storehouse and has, I think, been adequately supplied with several suggestions. He is welcome to choose among them.

Eugene


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## easymike29 (Aug 14, 2020)

For the benefit of math challenged and anyone else interested I have prepared a spreadsheet to calculate that .0627 dimension as well as 2 different ways to measure the mouth diameter. If anyone is interested I'll attach it in my next post.

Eugene


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## IanN (Aug 15, 2020)

willray said:


> Hi Richard.  Mostly, I was railing against the suggestion that "Don't overdimension a drawing is a useless holdover from the days of manual drafting", and that since "computers don't make drafting errors", this convention was now irrelevant.   I'm sure you are already familiar with the issues, but there are so many self-taught/only-ever-driven CAD jockeys that think that this is true, that I believe this bears being explicit about.
> 
> While computers can be reasonably argued to make far fewer simple math errors than human draftspersons, the prohibition against overdimensioning was only ever peripherally about _mistakes_.
> 
> ...



Hi Willray,

I agree with your comments but would add that the true, practical, reason for not “over dimensioning” is the tolerance problem:

Imagine a 100mm +/- 0.1mm long item with a hole 20mm +/- 0.1mm form one end - what is the “missing” 80mm dimension tolerance?

Ian


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## willray (Aug 15, 2020)

IanN said:


> Hi Willray,
> 
> I agree with your comments but would add that the true, practical, reason for not “over dimensioning” is the tolerance problem:
> 
> ...



Greetings IanN,

As you've described the part and feature, it's not over dimensioned   Were it over dimensioned, the its tolerance problem would be a subset of the "you get different dimensions (and tolerances) depending on which way you work the numbers around the part" problem.


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## willray (Aug 15, 2020)

easymike29 said:


> For the benefit of math challenged and anyone else interested I have prepared a spreadsheet to calculate that .0627 dimension as well as 2 different ways to measure the mouth diameter. If anyone is interested I'll attach it in my next post.



Please do.  I think the fact that the .225 countersink diameter is the specified dimension, and what ought to be the thing measured for compliance, is perhaps overlooked by many readers because they don't immediately see a way to measure that dimension.


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## easymike29 (Aug 15, 2020)

willray said:


> Please do.  I think the fact that the .225 countersink diameter is the specified dimension, and what ought to be the thing measured for compliance, is perhaps overlooked by many readers because they don't immediately see a way to measure that dimension.



My pleasure

Eugene


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## brotherbear (Aug 15, 2020)

Thank you very much, Eugene!


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## Richard Hed (Aug 15, 2020)

IanN said:


> Hi Willray,
> 
> I agree with your comments but would add that the true, practical, reason for not “over dimensioning” is the tolerance problem:
> 
> ...


There is always stack up too unless you fix it.


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## easymike29 (Aug 15, 2020)

brotherbear said:


> Thank you very much, Eugene!



You're welcome Brotherbear. If you have any suggestions for improving it let me know.

Eugene


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## L98fiero (Aug 16, 2020)

willray said:


> Please do.  I think the fact that the .225 countersink diameter is the specified dimension, and what ought to be the thing measured for compliance, is perhaps overlooked by many readers because they don't immediately see a way to measure that dimension.


The easy and, what my drafting instructor taught, appropriate way is to tolerance the important dimensions. If you're doing it in CAD, most if not all programs will allow you to set the default number of trailing zeros and you can put on the title block how to determine the general tolerances based on the number of zeros. Once you have that established, put special tolerancing instructions on the important ones. I've seen too many times when I have gotten drawings where everything is dimensioned to 3 decimal places, which generally means +/-0.005, even on 3" thick flame cut parts, and then you get someone with a CMM checking those parts!


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## wthomas (Aug 16, 2020)

Hi Ian:
     In Most system with the two dimensions at the limit would double the tolerance on the 80 mm dim.  That would be the case if the 
two limits (1) the bar long by 0.1 mm and the 20mm dim. short by 0.1 mm for a dimension of 80.2 mm and (2) the bar short by 0.1 mm
and the 20mm dim. long by 0.1 for a dimension of 79.8 mm.  Few people would catch the difference because they would just check the
given dimension but a CMM would show it.
     Also, just to show you that CAD work can be in error if the machine is not set to high number of places,here is a story told to me by a
toolmaker I know who became a checker because he was Good at his work.  When he was checking a large diameter,around 5 ft., indexing
plate that had about 25 to 30 station on it he found one station at the final position was off location.  He was doing the calculation to eight 
places to find the error on the CAD print.  When he went to the CAD Tool Designer, he had set the computer software to only six places not
thinking about the small error adding up that many times.
     By the way did you laugh also, about the countersink dimension?   90% of the time in the shop they just drop a screw in the first hole to
be sure it is deep enough.
                      Stuck at home in Mich. USA
                           Bill Thomas


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## IanN (Aug 17, 2020)

wthomas said:


> Hi Ian:
> In Most system with the two dimensions at the limit would double the tolerance on the 80 mm dim.  That would be the case if the
> two limits (1) the bar long by 0.1 mm and the 20mm dim. short by 0.1 mm for a dimension of 80.2 mm and (2) the bar short by 0.1 mm
> and the 20mm dim. long by 0.1 for a dimension of 79.8 mm.  Few people would catch the difference because they would just check the
> ...



Hello Bill,

Thank you for humouring me and posting calculated tolerance for the 80mm dimension - I know you already know my response and it is kind of you to act as the “stooge”

If the drawing shows a dimension of 80mm +/- 0.2 from the second end, then it is permissible to use this dimension on the drawing to locate the hole.

So let’s assume the work piece is 0.1 short (99.9mm) and the measured 80mm dim. is 0.2 long, all in spec if checked from the 80mm end, but measured from the 20mm end the 20+/-0.1 dim. would measure 19.7mm - out of spec.

It is impossible to correctly and unambiguously “over dimension” a drawing with assigned tolerances.

Now apply this logic to the countersunk hole:  You cannot specify three interrelated dimensions with tolerances (angle, diameter and depth of the countersink).  In the case of the original drawing the diameter and angle are specified.

As you correctly stated (voice of experience?) a sample with largest diameter and smallest angle would be the “gauge” to use

Thanks for sparring with me!

Ian


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## wthomas (Aug 17, 2020)

Hi Ian:
     Would 70 years of machining experience be enough for me to qualify?  I had worked in more shops
when I graduated from high school (3) then the leader-foreman in the last shop I worked in last year. 
I like to do the whole run from design, build, and runoff of a tool (hand tool, golf tool, die, mold,) or machine.  Largest run was 7,000 special
hand assembly tools for on the Auto Dealers in 9 months.   (OOPS)  I designed the clear coat / tinted coat paint system for the Ford plant in
Novi, Michigan 1992 that run for a number of years.  The Lord only knows how many cars the system painted and how long it lasted running
60 cars an hour. 
     If you would like to see something I made while working for Buick Engineering Google "10,000 Miles in 5000 Minutes" Video.  I machined
the special parts for refueling at 90 mile/hour.  Also, machined the roll bars for both cars.  I did both jobs on a Hyd. Tracer Lathe before the
time of NC.  
                                  Post your questions,  I  will try an answer them!
                                                Bill Thomas


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