# Spindle Threaded ER-40 Collet Chuck for the Atlas



## JAndrew (Nov 8, 2013)

Hello,

Chuck Fellows recently posted his ER-32 collet chuck for a mini-lathe that was backplate mounted. I appreciate his post a lot as he provided some good advice on getting the 8 degree taper for the collet precise.

I'm going to post progress on my collet chuck but be forewarned: "I have little or no idea what I'm doing really."

It's been over 10 years since I machined anything and even then I was billeted as an "Emergency Machinist" on submarines so my experience is minimal.

Here's the cross section collet chuck plan that I drew up in google sketchup:





I would strongly advise that anyone reading NOT use these plans. As I said I'm not really sure I know what I'm doing.

So far:
The first mistake I've made so far was ordering a piece of 12L14 that was 2.50" in diameter instead of 2.75". In order to keep the wall thickness "meaty" enough the flats of the nut will be a little further apart and not meet at pointed angles. I guess I should have finished those plans entirely before ordering the stock! :wall:

I am starting with my stock at a length of 3.50" instead of the 3.00" that is shown on my plans just in case I make any kind of mistake on the 8 degree taper.

Here's the progress:




I placed the stock in the four jaw chuck and dialed in the runout to within 0.005". Then faced the end and flipped it around. I dialed in again at 0.002" (due to the un-even rolled external surface).

The plan is to bore all the way through to a diameter of 1.125". I faced the 2nd end of the stock and center drilled. Then drilled to 0.375". The stepped it up to 0.500". Then stepped it up to 0.625". And finally drilled to 57/64 or 0.890".

The above picture shows the boring bar set up in the Aloris style tool holder with a 1/4" HSS bit.  The boring to 1.125" went well each time advancing the cross feed dial by 0.010". Each time though I did an additional "Spring" cut as I'm in no hurry. It seemed necessary as the boring bar is extended pretty far to bore through the full 3.50" length of the stock.

I had to stop there for the day. (New baby in the house so I only work during Nap-Times or in the early morning).

The plan moving forward is to bore the section for the spindle threads to 1.350" and thread 1.50"x8TPI. I included an extra large thread relief groove as I'm deathly afraid of running into the work.

Any suggestions or feedback is greatly appreciated. Don't know when I'll get back out to the shop.

Thanks,
-J.Andrew


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## kvom (Nov 8, 2013)

To get decent accuracy with the collets, everything needs to be concentric to the spindle.  Therefore I'd recommend the following:

1) After the initial non-critical bore and without removing the stock, bore and thread the spindle nose thread (1.5x8 ), and then face.

2) Screw the stock onto the spindle do all the other operations from there.

I suspect a 1.5" tap would require a lot of force, so I assume you'll be single-pointing the threads on the lathe.


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## JAndrew (Nov 8, 2013)

kvom said:


> To get decent accuracy with the collets, everything needs to be concentric to the spindle.  Therefore I'd recommend the following:
> 
> 1) After the initial non-critical bore and without removing the stock, bore and thread the spindle nose thread (1.5x8 ), and then face.
> 
> ...



KVOM,

That's exactly what my plan is. To cut 1.5x8tpi threads for the spindle I will be using a single point ground HSS bit that fits in the same boring bar above. I will not have the boring bar hanging out so far though for those threads. Once those are cut I'll be putting away the 4-jaw chuck. I ground the bit already.

I'm beginning to regret not making an externally threaded test piece beforehand so I could test my threads. It would have also served the purpose of giving me some well-needed practice at thread cutting. I read another post somewhere saying just to leave the part in the 4-jaw and flip it around to test the threads.

Thanks for the good advice.
-J.Andrew


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## JAndrew (Nov 8, 2013)

The wife took the baby to the mother-in-laws for a bit today so I was able to perform the next step of boring the threaded portion to the diameter required (1.350").

I swapped from the boring bar to a nice boring bit with a squared off tip so I could straight cut the shoulder. I used my ebay micrometer stop to set the depth at 1.250".

Here's the setup:
	

	
	
		
		

		
		
	


	




And here's the result:
	

	
	
		
		

		
		
	


	




I'm pretty impressed with the bore finish that this bit and the old atlas came out with. Not bad for a 70 year old machine! And the bit was a freebie with the lathe.

Next I need to cut the 0.250" wide thread relief groove to an ID of 1.500".

Here's a 0.250" bit I ground relief angles on but I'm wondering if it's a good idea to try to use a bit that wide...?
	

	
	
		
		

		
		
	


	




I'm kinda wondering if this is going to chatter too much? Should I be using a 0.125" wide bit twice instead?

Thanks in advance for any suggestions or advice!
-J.Andrew


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## cfellows (Nov 10, 2013)

Nice job on the chuck.   I would grind the end of that 1/4" tool bit down to a width of .090" or less.  Doesn't need to be much longer than the depth of your groove.

 Chuck


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## JAndrew (Nov 10, 2013)

cfellows said:


> Nice job on the chuck.   I would grind the end of that 1/4" tool bit down to a width of .090" or less.  Doesn't need to be much longer than the depth of your groove.
> 
> Chuck



Thanks Mr. Fellows! I will do just that. I'll probably cut that groove today and then remove the part and the 4-jaw chuck from the machine. I want to use my 3-jaw to make an externally threaded "test" piece out of PVC. Gives me some threading practice and will be easier to test my internal threads.

Thanks again for the advice and the drawing.
-J.Andrew


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## JAndrew (Nov 11, 2013)

Hello,

Didn't have much time to mess with the collet chuck on Sunday but I did manage to find the first problem with my plans and correct it. Here's Revision 2 of the plans:
	

	
	
		
		

		
		
	


	



I found that the spindle threads do not extend all the way to the stop collar. So in order for the back face of the collet chuck to meet the spindle stop collar I needed a thread relief BEFORE the threads as well as after to a depth of 0.3125". Luckily a minor correction. (I also removed the external diameter of 2.750" for hex nut flats as the piece of 12L14 is only 2.500" OD.)

This morning I was able to get the Atlas change gears swapped over to threading at 8TPI. I tested it out on my PVC test piece:
	

	
	
		
		

		
		
	


	



It was going well until I took to aggressive of a cut (0.010") and the flimsy PVC ripped out of the 3-jaw chuck.  It wrecked it. I'll make a new test piece this week and bulk up the section that I clamp in the chuck.

-J.Andrew


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## JAndrew (Nov 15, 2013)

Hello,

I was able to finish another thread tester out of PVC today:
	

	
	
		
		

		
		
	


	



PVC is a mess to cut! I was really surprised how easily it can be ripped out of a 3-Jaw chuck. I barely finished this one! On the last cut it grabbed again and twisted it out of the chuck again !!!  Luckily enough of it was undamaged that I can still use it to test the threads on the collet chuck.

I set to work next on making the grooving tool that Chuck Fellows was nice enough to draw up for me. Here it is:
	

	
	
		
		

		
		
	


	



I'm really glad Mr. Fellows advised me on this. Even at a cutting thickness of 0.090" it chattered like mad on the first cut! I surely would have broke something if I had tried to use the full 0.250" thick bit I had made originally.

To cut the chatter down I only advanced the grooving tool 0.030" each cut using my micrometer stop to reach the full width of 0.250". It work very well with no chatter. At one point though I did lose track of my math for advancing the micrometer stop. After some head scratching I was able to figure out how to measure the groove width using a 3/16" hex key. Here's the groove in progress:
	

	
	
		
		

		
		
	


	



No more progress today. The wife is making lasagna today so I'm on baby-watch. Hopefully will get to threading tomorrow.

-J.Andrew


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## JAndrew (Nov 15, 2013)

Hey! Just noticed this thread is displayed on the main HMEM page! I'm honored (even if it is completely random)

-J.Andrew


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## ShopShoe (Nov 16, 2013)

JAndrew,

I agree PVC is a mess:  Some thoughts.

If your supplier has the heavier PVC (Schedule 80??) Try that.

Turn a piece of wood to fit inside the PVC to provide some support.  (Yes, you can do it on a metal lathe. It is for support rather than beauty.) Turn a piece of stock longer than you need with a slight taper or a stepped OD. Put the PVC over it, then cut off the excess wood. Of course, you could also make a mandrel from from metal instead of wood.

--ShopShoe


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## JAndrew (Nov 16, 2013)

ShopShoe,

Thanks for the reply and the ideas. I even considered filling that second piece of PVC with some old epoxy resin I have. I had originally planned on PVC as a "quick and easy" way to make the thread tester. Ha! See how well that worked out for me?! I think I've spent more time on this PVC than on the actual project!

Live and learn. Hopefully I never have to turn PVC again but if I do...I'll use your ideas.

Thanks again,
-J.Andrew


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## chipenter (Nov 16, 2013)

If you drill 4 no 1\4" holes in the body 1\4" deep you can use the collet spanner insead of machining a hex  works a treat .


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## JAndrew (Nov 16, 2013)

chipenter said:


> If you drill 4 no 1\4" holes in the body 1\4" deep you can use the collet spanner insead of machining a hex  works a treat .



ChipEnter,

Thanks for the post! I think I will end up doing that. There's just not enough meat there for nut flats. The collet set I bought came with an R8 adapter for my mill and the spanner you are talking about:
	

	
	
		
		

		
		
	


	



I can also finish the collet chuck drawing dimensions now that I have the retaining nut.

I was afraid I had gotten a bad collet chuck nut when I first got it. If you look at the ring the collet snaps into it isn't ground concentric to the nut or the taper. I started stressing out about having to send the thing back and wait for a new one to come but all for not. I read elsewhere online the retaining ring is supposed to be ground off center so you can pop the collets in and out easily!

-J.Andrew


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## JAndrew (Nov 16, 2013)

Hello,

It's internally threaded! I was sweating bullets through the whole process but it worked! The first skim pass I took I did what I feared most; I ran the cutting tool into the back of the thread relief! Grrr!:wall:

Luckily I was able to put a bevel on there and no major damage was done.

Here's the single point tool ground to 60 degrees about 75% done with the threading:
	

	
	
		
		

		
		
	


	



It went very well after that first mistake and despite my nervousness. I was really hoping there would be a scraping noise I could use to tell when the cutting tool entered the relief groove but the whole process was very quiet. I used the back gears (~28RPM) and each pass advanced the compound rest 0.005". No chatter, no surprises. It came out very well. I took "spring" cuts without advancing the compound rest on the last 3-4 passes.

I used the PVC thread tester to see when it was getting close and then unscrewed the 4-jaw and flipped it around on the last 2 passes to check the final fit:
	

	
	
		
		

		
		
	


	



It fits! And it seats against the spindle's stop collar just as it's supposed to! I couldn't think of anymore reasons to keep it in the 4-jaw after that.

After changing back to "feed" gears from "threading" gears I faced the end I haven't seen in the last 2 weeks and turned the final OD. I had to remove one way wiper from the carriage and angle the tool bit to be able to reach the spindle end of the collet chuck.

Buying the wrong size piece of 12L14 bit me again as there wasn't enough material there to maintain the OD at 2.500". It measures out at 2.490".  That's the nice thing about machining at home...no one will ever come after me and check my measurements!:hDe:
Here's the last shot before I bore the taper tomorrow and externally thread:
	

	
	
		
		

		
		
	


	



The finish on the OD is inconsistent at best . That's the rigidity issue I suppose everyone is talking about with Atlas lathes...? Like the Ride Maintenance Mechanics at LegoLand used to say, "It ain't goin' to the &%[email protected] Moon."

-J.Andrew


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## Wizard69 (Nov 17, 2013)

JAndrew said:


> No more progress today. The wife is making lasagna today so I'm on baby-watch. Hopefully will get to threading tomorrow.  -J.Andrew



Homemade Lasagna is a valid reason to mis a day in the workshop.  For me though the carbs would mean missing another day due to high sugar levels.   I do mis Lasagna and a bunch of other high carb foods!


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## JAndrew (Nov 17, 2013)

Wizard69 said:


> Homemade Lasagna is a valid reason to mis a day in the workshop.  For me though the carbs would mean missing another day due to high sugar levels.   I do mis Lasagna and a bunch of other high carb foods!



Wizard69,

The lasagna was great. There were no leftovers:wall:

-J.Andrew


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## JAndrew (Nov 21, 2013)

Hello,

I finally got some shop time in. Quite a productive day.

I was having a good deal of trouble with chatter while trying to bore the internal taper for the collet . I found out a good deal about proper spindle speeds. Turns out I was running the spindle speed at about half what is should have been. Also found that the gib screws for the compound rest and cross-slide needed to be tightened down to the point of being difficult to turn by hand in order to get the rigidity I needed. Luckily I had plenty of passes to test all these variables out before the finish cut. Also swapping to the boring bit I used before instead of the boring bar setup seemed to help a good deal. Here's the setup:
	

	
	
		
		

		
		
	


	



At this point the part was still closer to 3.5" in total length to allow me a good deal of test cuts while boring. Everything I've read about these collet chucks has said to keep them as short as possible for rigidity. Since this is a project to help me re-learn lathe skills I decided to use a parting tool to shorten it closer to the 3.0" length rather than a bunch of facing.

The parting operation went extremely well! No chatter or squealing. But man alive does it make a mess! Here's the parting tool afterward:
	

	
	
		
		

		
		
	


	



The surface was so smooth I didn't even face it when completed.

Back to boring. Over and over! Hand cranking the compound rest with the gib screws very tight! Ugh! Lubricated with WD-40 and the finish cut came out awesome! It fits!!!:
	

	
	
		
		

		
		
	


	



The bore seemed a little off angle at first but after deburring the outer lip the collet fit so well I didn't even bother doing a blue check. I did smooth the bore with 120 grit sand paper and then again with 400 grit for a smooth polished surface that the collet can slide well on.

Next I turned down the area for the external 50x1.5mm threads to a diameter of 1.968":
	

	
	
		
		

		
		
	


	



I finally figured out how to grind a HSS bit and angle it in the AXA holder so I could turn down the diameter and face the edge with just that tool! Grinding bits is a long process for me. Most of the time is head scratching but it also goes slower because I'm using a belt sander instead of a grinding wheel.

Finally I added the relief groove using the parting tool to a width of 0.125" as such:
	

	
	
		
		

		
		
	


	




Hopefully I'll do the external threading tomorrow. Metric threading...I've verified I have the change gears needed and from what the Atlas manual says, I'm in for a long day of hand cranking the spindle in reverse. The manual says I'm not to disengage the carriage from the leadscrew until the threads are done. No reversing motor .

I'm considering using the Armstrong style threading tool to do this threading instead of grinding another bit for the AXA. I'm wondering if there's any reason I shouldn't try using this tool...?

Thanks for reading and thanks in advance for any advice you can offer.

-J.Andrew


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## mu38&Bg# (Nov 21, 2013)

I did a lot of metric threads on my old Atlas-Craftsman. It's not a big deal cranking that spindle back. If you intend to do it often, make one of the spindle crank handles that goes in the back of the headstock. http://www.homemodelenginemachinist.com/f28/spindle-crank-threading-7047/


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## JAndrew (Nov 21, 2013)

dieselpilot said:


> I did a lot of metric threads on my old Atlas-Craftsman. It's not a big deal cranking that spindle back. If you intend to do it often, make one of the spindle crank handles that goes in the back of the headstock. http://www.homemodelenginemachinist.com/f28/spindle-crank-threading-7047/



DieselPilot,

Thanks for the link. That guy does some really cool projects on his website Dean's Photographica. When I bought the lathe I was disappointed it didn't have a quick change gearbox but justified it by saying, "I don't plan on doing much threading anyway...":wall:

Here I am threading right off the bat! I will add this to my long list of projects.

Thank again,
-J.Andrew


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## techonehundred (Nov 21, 2013)

Your Chuck is looking good and you're almost there.   

When I did my er40 chuck. 
http://www.homemodelenginemachinist.com/f13/trials-tribulations-construction-lathe-collet-chuck-17083/ (Shameless Brag) :hDe:

  I did all of the threads with the hand crank.  Doing the metric threads were very easy as they are not very deep.  I really like mine and was one of the best decisions I made in building it. 

 Just waiting now to see yours finished.

Anthony


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## DICKEYBIRD (Nov 21, 2013)

Looks great Anthony, nice work!Thm:

One thing though...put a piece of drill rod or an end mill shank in a collet & check the taper.  ER collets are so flexible you'll think your taper's perfect but not necessarily true without something in the collet bore.


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## JAndrew (Nov 21, 2013)

techonehundred said:


> Your Chuck is looking good and you're almost there.
> 
> When I did my er40 chuck.
> http://www.homemodelenginemachinist.com/f13/trials-tribulations-construction-lathe-collet-chuck-17083/ (Shameless Brag) :hDe:
> ...



Anthony,

Thanks for the post and the link to your thread. I came really close to making the same mistake you did of having the compound rest 90degrees off! I did one pass before I realized it! Your finished project looks good. In retrospect I should have done an external taper like you did. Maybe I'll knurl the outside just to round out the project some.

I will probably hand crank the spindle as it gets close to the thread relief.

Thanks again for the post.
-J.Andrew


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## JAndrew (Nov 21, 2013)

DICKEYBIRD said:


> Looks great Anthony, nice work!Thm:
> 
> One thing though...put a piece of drill rod or an end mill shank in a collet & check the taper.  ER collets are so flexible you'll think your taper's perfect but not necessarily true without something in the collet bore.




DickeyBird,

Thanks for the advice. I got all worried and ran out there to try what you said. I still feels good and snug. I did a quick blue check after all (though it was actually with a green sharpie). It transfered a good even amount of green ink to the middle section of the collet and seems to be good to go.

I didn't even think about how they might be flexing. Thanks!

-J.Andrew


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## JAndrew (Nov 24, 2013)

Hello,

I haven't been able to cut the final metric threads yet (stuck at work this week). I was however able to finish up final revisions to my drawing. I added the width dimensions of the 50x1.5mm threads and thread relief. Here it is:
	

	
	
		
		

		
			





I would caution anyone who might try to use these plans that the taper bore major diameter and width of the 50x1.5mm threads will be specific to the nut you use!

I'm sure anyone taking on this project could come up with a much more intuitive design anyway 

Thanks,

-J.Andrew


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## JAndrew (Nov 25, 2013)

Hello,

It's finished! The nut fits extremely well on the external threads. Here's a shot of the tool I ground to cut the threads:
	

	
	
		
		

		
		
	


	



I had to offset the point to the left so I wouldn't run into the other side of the thread relief. It wasn't all that much handcranking of the spindle after all. I only turned it by hand in reverse since the backgears are nice and slow during the threading. I wanted to make sure I didn't disengage the half nut before the operation was complete on accident so I employed this device to keep me in check:
	

	
	
		
		

		
		
	


	



There's one thing I just can't figure out that I'm hoping someone can help me out with... Both times that I've threaded on this machine the threads are finished with much less compound feed than in the calculations. We figured earlier in this post that the total compound feed (at 29degrees) would be 0.055"-0.068" (depending on the nut thread). When I finished however I had only advanced the compound rest 0.038" and the threads were done...? It was the same story on the internal threads I first did; only about 60% of the calculated values...? Anybody know what I'm missing here???

Either way it was fairly evident when it was time to start testing the nut and it fits very well after a couple "spring cuts".

I tested the final runout of the chuck with a 0.75" piece of brass scrap that I had previously turned in the 4-jaw. The runout was just about 0.001". I am very pleased with that number! I was expecting ~0.003"!  Here's that:
	

	
	
		
		

		
		
	


	



I only got to check it with one other collet and a 5/16" drill blank. It also checked out at 0.001"!

Here's the finished project:
	

	
	
		
		

		
		
	


	




All in all this was a great project to re-learn all this stuff. I'd recommend it to anyone who's just starting out in machining. It's a great way to learn a bunch of lathe skills and now I have a precise holder for parts from 0.100"-1.125" that allows stock to be extended through the spindle bore! The total project time was about 10 hours. Most of that was scratching my head to figure things out and grinding tool bits slowly on a belt sander. The lathe probably only ran about 2 hours of all that time!

Someday when I have a dividing head I think I will cut 0.250" grooves that match those on the nut. And I might throw some knurling on there too so turning the spindle by hand is easier. That would really round out the project skill set.

My next project will be a set of simple right hand and left hand tangential toolholders with 1/2" shanks. I'll post what I can on those and then on to making my first simple single oscillator.

Thanks to anyone who offered advice or followed this thread.
-J.Andrew


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## Swifty (Nov 26, 2013)

Quote. There's one thing I just can't figure out that I'm hoping someone can help me out with... Both times that I've threaded on this machine the threads are finished with much less compound feed than in the calculations. We figured earlier in this post that the total compound feed (at 29degrees) would be 0.055"-0.068" (depending on the nut thread). When I finished however I had only advanced the compound rest 0.038" and the threads were done...? It was the same story on the internal threads I first did; only about 60% of the calculated values...? Anybody know what I'm missing here. End quote.

Your not getting mixed up with total difference between major and minor diameter are you? You are only coming in from one side and the graduations on the top slide are actual movements. If you have the room, you can always turn down a short section at the start to the minor diameter, when you start to touch this, you are at depth.

Paul.


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## Swifty (Nov 26, 2013)

Just checked the thread sizes, the actual depth of the thread, allowing for flats on the crest and root of Pitch/8 (.0073"),  will be .0383".
There seems to be something wrong with your initial calculations, however everything turned out OK.

Paul.


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## mu38&Bg# (Nov 26, 2013)

Swifty said:


> Just checked the thread sizes, the actual depth of the thread, allowing for flats on the crest and root of Pitch/8 (.0073"),  will be .0383".



He used a tool with a sharp point.

We calculated .048" infeed @30° for the M50x1.5 in the other thread. I think it's just tolerance that causes the discrepancy, but have to check the actual clearances for the limits of the threads. If the nut is on the loose side, then the external thread doesn't have to be as deep. You may find that another nut won't fit if it was made just deep enough for this nut. If you were really concerned you'd measure the thread pitch diameter to be certain it falls within the specification to ensure every nut fit.

Greg


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## Swifty (Nov 26, 2013)

Don't want to labour the point, but infeed using the top slide at 30deg with a sharp pointed tool, taking the outside dia to a sharp point will be 0.059", and infeed using the cross slide only will be 0.051". Simple trig gives these dimensions. Of course, there are a lot of variables, what tolerance was the nut made to, the top of the thread is never a sharp point etc. always best to get near and then start checking with the nut.

Paul.


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## mu38&Bg# (Nov 26, 2013)

http://www.homemodelenginemachinist.com/f26/amateur-question-metric-threading-calculations-22196/


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## JAndrew (Nov 27, 2013)

Swifty and DieselPilot,

Thanks for the input. I think the discrepancy between measurements is what TinFalcon hit upon with the differences in standards used for metric threads. These threads (on the nut) didn't appear to have any flats in the valleys or on the the crests.

Also I think I forgot to account for the initial "skim" cut I took to check the thread pitch. While the compound feed dial was set to "zero" during this skim cut there was already a depth infed to make this cut. Could have been anywhere from 0.001" to 0.010" I'm guessing....?

Either way the threads came out perfect and I don't need to reproduce them anymore.

Thanks again for your inputs. I got to use the collet holder yesteday to make some steady rest fingers with live bearings. It held some 0.125" drill rod well enough that I was able to part pieces of it off with a sharp pointed tool.

Very pleased with the project.
-J.Andrew


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## JAndrew (May 15, 2014)

Here's the final chapter for my ER40 collet chuck:

I was finally able to borrow a rotary table from work and cut 12 flats onto the collet chuck. 
	

	
	
		
		

		
		
	


	




Now I can use it as a collet block. I can throw it in a milling machine vise and index parts with 1,2,3,4,6 or even 12 sided cuts.

I'll be making some replacement square head bolts for the Atlas lathe here pretty soon.

Thanks all,
-J.Andrew


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