Might it be simpler to remake both screws and change the knurled locking screw 
to a more conventional thread?

Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031

-----Original Message-----
From: andy pugh <bodge...@gmail.com>
Sent: Thursday, May 11, 2023 12:15 PM
To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net>
Subject: [Emc-users] Suggestions for cutting an odd little thread.

[EXTERNAL EMAIL] Be sure links are safe.

The Rivett 608 lathe has knurled screws to lock the micrometer dials.
These are quite long, going down the centre of the feedscrew and pushing out a 
radial wedge.

I am making some new feedscrews and have realised that these screws are 
threaded 0.190" x 30

This is probably #10-30 though 3/16 is possible. However I have never found a 
screw to be _above_ nominal diameter, so think it is #10-30.

#10-30 is listed as an old ASME (pre-war) standard. But finding the taps in the 
UK seems about as easy as you would expect.

So, how else to cut the thread? Maybe a very tiny thread mill?
Single-point cutting might work, but it's a rather deep thread for the 
diameter. And I don't have a suitable tool (such as
https://www.ebay.com/itm/383646508366 ). Thread-milling would be an excuse to 
add live tooling to the lathe, and an almost-suitable cutter is affordable: 
https://www.shop-apt.co.uk/single-tooth-thread-mills-for-general-use-internal-60-partial-profile/internal-partial-profile-60-thread-mill-05-08mm-pitch.html

--
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed for 
the especial use of mechanical geniuses, daredevils and lunatics."
- George Fitch, Atlanta Constitution Newspaper, 1912


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