Cutting an ACME thread

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Cutting an ACME thread

This topic has 9 replies, 6 voices, and was last updated 16 February 2014 at 15:31 by RobC.

Viewing 10 posts - 1 through 10 (of 10 total)

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13 February 2014 at 21:43 #143826
RobC
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@robc77385
I am looking to cut a small length of steel bar with an ACME thread 3/8" x 12 and then make the equivalent nut for it (from Delrin). I have access to a Myford ML7 with the screwcutting gearbox and I know it is possible.

I could mess about and grind my own tool, but wondered if there is an insert toolholder combination that would enable me to obtain the correct form. Everything I see is huge and I need small stuff. My previous attempts with hand-ground threading tools were a bit of a disaster (Buttresss threads).

I have searched through the site info, but not found anything coming to hand readily.
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13 February 2014 at 21:43 #15690
RobC
Participant
@robc77385
13 February 2014 at 22:15 #143829
Anonymous
Cutwel do a 12tpi ACME insert in the standard 16mm size, so easy enough to cut the external thread. The nut being Delrin it should be simple enough to make a tap for same. It probably wouldn't need to be hardened. Flutes and relief on the tap could be done by hand with a file.

Regards,

Andrew
13 February 2014 at 22:16 #143830
julian atkins
Participant
@julianatkins58923
hi RobC

if you have access to back copies of ME circa 1986 have a look at roy amesbury's reverser for PRESIDENT and how he ground the tool and cut the multi start thread. i am afraid you will have to grind up the tool yourself, though for a one off job it could be done with silver steel filed to shape and then stoned to a nice finish.

i dont know what your thread is for, but a quick dodge for appearance is to run a file over the tops of the thread to simulate acme threads.

cheers,

julian
13 February 2014 at 22:28 #143832
Muzzer
Participant
@muzzer
I saw a thread on another forum recently that described splitting the unthreaded nut lengthways into 2 halves and then gently heating the leadscrew and clamping the nuts so that they moulded to the leadscrew and each other as they melted.

Just found it – it was Jim Schroeder **LINK**

Worth a go?
14 February 2014 at 02:06 #143838
_Paul_
Participant
@_paul_
Looks like Mr Schroeder has based his work on Evan Williams original post on Acetal Nuts

Regards

Paul
14 February 2014 at 22:37 #143954
Muzzer
Participant
@muzzer
Yes, they are both pretty good illustrations of the technique although I suspect this isn't the first time the approach has been thought of. Cast in place methods were probably commonplace when white metal was used for bearings.

Murray
14 February 2014 at 22:48 #143958
John Stevenson 1
Participant
@johnstevenson1
And Evan Williams based his on a post by a guy called Daryl over on Practical Machinist.

Not really a lot new in this world. George Bullis the editor of HSM made one and wrote it up as his editorial in Digital Machinist this quarter. I wrote him to explain how I can do them in one piece, no splits and he's asked for an article on it.
15 February 2014 at 01:34 #143964
_Paul_
Participant
@_paul_
Posted by John Stevenson on 14/02/2014 22:48:26:

I wrote him to explain how I can do them in one piece,

Does anyone offer them commercially?
16 February 2014 at 15:31 #144106
RobC
Participant
@robc77385
I would be interested to find out how to do them with no splits, as I need a fairly thing rectangular nut and I concerned that having a split one would compromise it's strength.
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