On Sep 20, 4:19 pm, F. George McDuffee gmcduf...@mcduffee-
associates.us wrote:
On Thu, 20 Sep 2007 11:11:10 -0700, Gerry
wrote:



On Sep 20, 10:09 am, Wes wrote:
Gerry wrote:
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

Have you checked out MSC?http://www1.mscdirect.com/CGI/GSDRVS...00000029342574

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

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

==========
Any chance you can build the nutup with some of the newer
compounds such as Moglice or Turcite? http://astro.umsystem.edu/atm/ARCHIV...wfriction.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
seehttp://www.moglice.com/newsite/pages/wrotethebook.htmlfor
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 onhttp://lindsaybks.com/bks7/babb/index.htmlhttp://lindsaybks.com/bks4/babbitt/index.htmlhttp://lindsaybks.com/dgjp/djgbk/babbitt/index.html

also seehttp://www.practicalmachinist.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=p...

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.

What a great idea! I have a spare but worn nut that I could play with.
Many thanks!