# 4TPI Tap in 5/8 inch in ACME



## timber (11 Oct 2016)

I am after a 5/8 inch 4tpi tap.ACME

It is to be used to cut a thread into some Delrin. Need to make a new half-nut for a Legacy wood lathe. At a push a short bit of leadscrew would do.I could shape it up to cut the thread.
If you have such a thing to sell let me know
Timber


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## bugbear (11 Oct 2016)

timber":vpbcvojh said:


> I am after a 5/8 inch 4tpi tap.ACME
> 
> It is to be used to cut a thread into some Delrin. Need to make a new half-nut for a Legacy wood lathe. At a push a short bit of leadscrew would do.I could shape it up to cut the thread.
> If you have such a thing to sell let me know
> Timber



I don't think such taps are made, since the cutting forces would be extremely high.

EDIT; I'm wrong; some Acme taps are made;

http://www.tracytools.com/taps-and-dies/acme-taps

A screwcutting metal lathe owner may be able to cut you a new half nut though.

BugBear


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## marcros (11 Oct 2016)

Have you seen this http://bbs.homeshopmachinist.net/thread ... 554d9404eb

may or may not be relevant to your need.


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## timber (11 Oct 2016)

marcros":yvqrv8gy said:


> Have you seen this http://bbs.homeshopmachinist.net/thread ... 554d9404eb
> 
> may or may not be relevant to your need.


Thanks marcros, I will have to try that, a great help

bugbear 
Thanks but I could not see a 4tpi acme


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## Retire2004 (11 Oct 2016)

Hi Timber, 4TPI on a 5/8" dia. sounds a very course thread! It could actually be an 8TPI two-start thread. How far does the carriage move for 1 turn of the leadscrew? What is the distance from one thread form to the next? (1/4" or 1/8") Is the thread RH or LH.
Regards, Tudor


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## timber (11 Oct 2016)

Retire2004":21q1knq2 said:


> Hi Timber, 4TPI on a 5/8" dia. sounds a very course thread! It could actually be an 8TPI two-start thread. How far does the carriage move for 1 turn of the leadscrew? What is the distance from one thread form to the next? (1/4" or 1/8") Is the thread RH or LH.
> Regards, Tudor



Hi Tudor
It is from the USA
It is a right hand thread and one turn moves the carriage 1/4 inch ----It is not a two start thread
Regards
Timber


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## Retire2004 (11 Oct 2016)

Hi Timber, Thanks for the info. Could be a "stub" Acme thread, this is a lower profile used when a stronger root dia is required. For a 4 TPI this would have a basic thread depth of 0.075" pitch instead of 0.125" on a Standard Acme. As already stated, a normal 5/8 dia would have a min of 8 TPI. Maybe Legacy make it a non-standard in order to justify crazy prices for spares!
Tudor


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## bugbear (11 Oct 2016)

timber":4m3zguqa said:


> marcros":4m3zguqa said:
> 
> 
> > Have you seen this http://bbs.homeshopmachinist.net/thread ... 554d9404eb
> ...



Hence my use of the word "some"

BugBear


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## timber (12 Oct 2016)

Retire2004":34z6nvkk said:


> Hi Timber, Thanks for the info. Could be a "stub" Acme thread, this is a lower profile used when a stronger root dia is required. For a 4 TPI this would have a basic thread depth of 0.075" pitch instead of 0.125" on a Standard Acme. As already stated, a normal 5/8 dia would have a min of 8 TPI. Maybe Legacy make it a non-standard in order to justify crazy prices for spares!
> Tudor



Hi Tudor
The depth is around the .090 mark
I agree I am sure it a closed shop ,have to buy from them.
they don't seem to answer emails or respond to most questions asked by other owners of Legacy lathes.
I did think about cutting a short length of the leadscrew to make a tap. I don't seem to use the full length of 6 foot 
Timber


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## chaoticbob (12 Oct 2016)

Hi Timber. Just looked at the thread chart on my lathe - it does 4TPI. If all else fails, I'd be happy to have a go at this for you. I've made custom metric taps before, but never had to cut an ACME tap, so cost to you would be material and postage - what I'd get out of it would be some new experience.
Rob.


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## bugbear (13 Oct 2016)

chaoticbob":2pxrc1g2 said:


> Hi Timber. Just looked at the thread chart on my lathe - it does 4TPI.


Many lathes have 8 TPI leadscrews, so it's not a complex change wheel calculation.  

It might be easier to cut the required half-nut than make a hard-to-use tap to cut the half-cut.

BugBear


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## timber (13 Oct 2016)

chaoticbob":lwvbdzzc said:


> Hi Timber. Just looked at the thread chart on my lathe - it does 4TPI. If all else fails, I'd be happy to have a go at this for you. I've made custom metric taps before, but never had to cut an ACME tap, so cost to you would be material and postage - what I'd get out of it would be some new experience.
> Rob.



Hi Rob
I have just sent you a P.M.
Rich


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