On 5/11/23 12:16, andy pugh wrote:
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.
Go ahead and say it, pure unobtainium. ;o) I've not heard of 10-30
before. We have 10-24 and 10-32, once common in 19" equipment racks but
even those seem to have switched to 3/16-24 screws in the last 30 years
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 ).
One could say they are quite proud of those.
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
That's much more reasonable. Is it long enough...
Since you're making the feedscrews, any chance you could do these in 3
to 5mm metric? Think of it as modernizing the design.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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