1/2 X 8TPI Acme

Sometime in the future I will need to make a new crossfeed nut for my old Sheldon lathe. Didn't seem like a big deal until I realized that
duplex taps are not available in 1/2"X8tpi Acme.Y'all have any suggestions? I really don't want to have to grind a tool to cut Acme threads that small. I think I'd farm the job of making the nut out instead if that was the only way. I could convert to 1/2"X10tpi but I'd have to make a new dial graduated to suit as well
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Maybe you can use an existing nut and modify it to your needs.
Try: http://www.greenbaymfgco.com/catalog.php
Also, I don''t know about Sheldon lathes, but I see new crossfeed nuts for Atlas lathes on Ebay from time to time.
Pete Stanaitis ----------------
Gerry wrote:

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Have you checked out MSC? http://www1.mscdirect.com/CGI/GSDRVSM?PACACHE0000029342574
I work midnights so I'm going to bed. I'll look further this afternoon. It is on my list of things to aquire.
Wes
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Neither have 1/2 X8tpi. 1/2 X10 seems popular as does 1/2X13. The last nut I bought from the Sheldon dealer was over $200 for a rough cast iron with rough threads. For that price I'd expect it to fit snug and be adjustable for wear to boot. 1/2 X8 threaded rod is available from MSC
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wrote:

=========Any chance you can build the nutup with some of the newer compounds such as Moglice or Turcite? http://astro.umsystem.edu/atm/ARCHIVES/JAN04/msg00101.html http://www.moglice.com/newsite/pages/lowfriction.html
<snip> The elevating nuts for the headstock were also injected with Moglice. The old babbitt was melted out of the steel nut bodies. The lead screws were milled to provide an accurate lead and aligned on the headstock through the nuts (figure 12). The Moglice was then injected and allowed to cure (figure 13). The next day the screws were removed from the nuts revealing finished Moglice threads inside the nut, as seen in figure 14. This saves either the making of new nuts or the buying of new screw and nut assemblies. The replication material will faithfully reproduce any thread geometry. It does not matter whether the screw is metric or standard, fine-pitch or multi start high helix, the molding technique makes it easy to fit the nut. Being able to reuse the old nut body is especially economical when the body is difficult to machine or the delivery time for a new one is too long, as is often the case with expensive bronze nuts. <snip> see http://www.moglice.com/newsite/pages/wrotethebook.html for entire article
http://diamant.ph/en/referenzen/details/all "2.) Tested Moglice applied to the nut of an Acme screw for coefficient and wear. Results: Satisfactory.No apparent wear after many hours of continuous running under heavy loads. This nut is still in Service at customer's plant."
http://www.mogorehab.com/repair.php Moglice can be successfully used to repair both ball and acme screws by removing the balls (or acme threads), remounting the nut concentric on the screw, and molding new threads to fit the original or requalified screw. This 48 hour process delivers you a replacement assembly with these advantages: LOW FRICTION, MINIMUM BACKLASH (less than .001), EXTENDED LIFE, AND COMPETITIVE PRICE.
One of the babbit books that Lindsay sells describes using babbit for the half nut, and I see no reason it wouldn't work with a cross slide. click on http://lindsaybks.com/bks7/babb/index.html http://lindsaybks.com/bks4/babbitt/index.html http://lindsaybks.com/dgjp/djgbk/babbitt/index.html
also see http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=print_topic;f=1;t6534
Unka' George [George McDuffee] ===========Merchants have no country. The mere spot they stand on does not constitute so strong an attachment as that from which they draw their gains.
Thomas Jefferson (1743-1826), U.S. president. Letter, 17 March 1814.
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On Sep 20, 4:19 pm, F. George McDuffee <gmcduf...@mcduffee- associates.us> wrote:

What a great idea! I have a spare but worn nut that I could play with. Many thanks!
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Just curious---is that LH or RH? Seems like most of the crossfeed screws/nuts I've dealt with have been LH.
Bill
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Get some O1, turn a long taper on it, thread it 1/2"x8tpi acme, gash it, harden it and use it as a tap. Seriously, that worked for me (except I needed 1/2"x10tpi at the time).
Mark Rand RTFM
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use a small boring bar & chase an internal thread

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http://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=1;t1140;p=0
Scroll down to rke[pler . He made a 1/2-8 LH tap. Perhaps he would loan it or sell it to you. He is active on the list.
Wes
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