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Old 02-08-2019, 05:25 PM   #1 (permalink)
 
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Default How to make acme style threads for cap

Hi All,

I am looking for basic instructions on how to make acme style threads on a metal lathe. Also I wonder what is the correct piece to use for the thread cutting...?
Here you can see attached a fine example of acme threads, I would love to get that same result as in the first pic where the black part seems to go all the way inside the barrel.
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llk.jpg   thread1.jpg  

Last edited by carandacher; 02-08-2019 at 05:27 PM.
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Old 02-08-2019, 07:46 PM   #2 (permalink)
 
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There are numerous YouTube videos on single pointing both internal and external acme threads. You May need to go a little bit beyond that to figure out the relationships between pitch and thread depth, etc.

External thread tooling should be relatively inexpensive, but you may need to spend a bit more for internal tooling. at these small diameters.

Bill
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Old 02-08-2019, 09:37 PM   #3 (permalink)
 
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This would also work on a metal lathe putting the bit in the head stock.

http://content.penturners.org/librar..._threading.pdf

You could also grind internal and external bits and thread the normal way on a metal lathe. You would want a bit about .050 in width and cut at 10 threads per inch.
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Old 02-08-2019, 11:30 PM   #4 (permalink)
 
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With a metal lathe you could turn external threads on drill rod and make your own taps. Turning ID threads for small diameters is difficult. Iíve done this for normal threads and I assume it would work for ACME threads. If interested, let me know and I could walk you through the steps.

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Old 02-09-2019, 12:26 AM   #5 (permalink)
 
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jalbert seems to have mastered the process. Message him and see if he has a few tips he can share beyond what has been suggested so far.

Green and silver
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Old 02-11-2019, 09:05 AM   #6 (permalink)
 
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Quote:
Originally Posted by Curly View Post
jalbert seems to have mastered the process. Message him and see if he has a few tips he can share beyond what has been suggested so far.

Green and silver
Those are actually square threads (no wall angle), not acme. I grind my own tools, so Iím not sure whatís commercially available. Besides taking a lighter depth of cut per pass, I find them no different to cut than 60 degree threads.
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Old 02-11-2019, 09:35 AM   #7 (permalink)
 
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Quote:
Originally Posted by jalbert View Post
Quote:
Originally Posted by Curly View Post
jalbert seems to have mastered the process. Message him and see if he has a few tips he can share beyond what has been suggested so far.



Green and silver


Those are actually square threads (no wall angle), not acme. I grind my own tools, so Iím not sure whatís commercially available. Besides taking a lighter depth of cut per pass, I find them no different to cut than 60 degree threads.


What are you using for your bit geometry for cutting your threading tool? I was thinking a cutoff tool but wasnít sure if it would have the necessary side clearance as it progressed along the thread.

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Old 02-11-2019, 09:46 AM   #8 (permalink)
 
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You would probably get the best results from grinding some sort of helix angle . No machinist am I, so I don’t have a good explanation of the specifics. I just trial and error it.
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Old 02-11-2019, 09:54 AM   #9 (permalink)
 
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I found this on youtube

https://www.youtube.com/watch?v=Ioi0mIVfvHA
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Old 02-11-2019, 12:39 PM   #10 (permalink)
 
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If you're interested in single pointing a true acme threads you are going to need specialized tooling. Cheapest source is probably Ebay:

https://www.ebay.com/sch/i.html_from...+tool&_sacat=0

This link shows a couple of solid carbide 12 tpi acme tools that will fit inside a pen cap for around 35 bucks.

If you already have some sort of insertable toolholder you can probably find acme inserts that will fit it for the external threads.

Taps for the internal threads are fairly expensive. The ones at Victornet and McMaster will only work for through holes. I'm just making this up but it seems to me that the loads on something as thin as a pen cap would be dangerously high when tapping an an acme thread.

Single pointing a female thread isn't all that difficult. John Albert does it on every pen that he makes, and I've done it on many.

Another tooling source that is a lot more expensive but very good is Thinbit:

Threading and Chamfering Products

FWIW

Bill
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