Cutting an ACME thread

[RobCParticipant @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.

[RobCParticipant @robc77385]

[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

[julian atkinsParticipant @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

[MuzzerParticipant @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?

[_Paul_Participant @_paul_]

Looks like Mr Schroeder has based his work on Evan Williams original post on Acetal Nuts

Regards

Paul

[MuzzerParticipant @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

[John Stevenson 1Participant @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.

[_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?

[RobCParticipant @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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