Print reading question

[Richard Hed]

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.

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.

 

[William May]

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.

 

[Richard Hed]

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.

 

[William May]

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.)

 

[goldstar31]

(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

 

[Richard Hed]

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.

 

[willray]

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.

 

[William May]

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

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.

 

[William May]

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?



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?



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.

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.

 

[Richard Hed]

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.

 

[Richard Hed]

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.

 

[awake]

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.)

 

[Richard Hed]

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.

 

[Asm109]

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.

 

[easymike29]

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

Eugne

 

[haakonpe]

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

 

[Richard Hed]

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.)

 

[Asm109]

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.

 

[Richard Hed]

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.

 

[Asm109]

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.