In article . com,
wrote:
My 5914 had about 2.25 INCHES of backlash in the center of the lead
screw when I bought it. I think the machine was only being used to cut
off parts (not using the middle part of the lead screw) at the end of
its commercial life.
Hmm ... mine (a Clausing 5418 -- 12x24") had pretty bad wear in
the middle of the leadscrew, though not quite that bad.
My machine came with a bed turret, instead of a tailstock. (I had
to chase down one to fit it later. I sometimes do batches of parts with
the turret mounted, and a typical example would be (using rod stock fed
through the spindle in collets):
1) Set workpiece length against stop/center drill
2) Center drill the end using the same tool, with center drill
extended.
3) Knurl OD to length with a T-bar knurler.
4) Turn part of length to smaller diameter with roller box tool in a
single pass.
5) Thread that length to shoulder in a single pass with Geometric
die head.
6) Drill center through length to tap drill size with bit in a
Jacobs chuck
7) Tap to depth with tap in releasing tap holder.
To this point, nothing has used the carriage or cross-slide.
8) Use parting tool in cross-slide to undercut the end of the
threads against the shoulder. Carriage is positioned with a
turret bed stop.
9) Use parting tool to part off workpiece with carriage positioned
using another station on the turret bed stop.
10) While steps (8) and (9) are being done, belvel selected points
with a hand-held file.
11) Catch rather warm workpiece in a wire basket.
12) If there is sufficient stock length, Go back to step (1) above
and repeat.
So -- note that there is no wear on the longitudinal leadscrew
for threading, as that is done with the Geometric die head (and much
more quickly, FWIW. ) And the cross-feed is powered from a sliding worm
gear keyed to the leadscrew's key.
This is the kind of work which the lathe had been used for most
of its life. The threading dial was still in one of the drawers --
never mounted. (It is now mounted, of course, and gets regular use.)
As a result, the cross-feed leadscrew was nearly worn out
(V-points on the threads, with lots of width between threads), and the
threading (longitudinal) leadscrew was pretty much unused. I have no
idea how many cross-feed leadscrews and nuts that machine had been
through, but very little carriage motion (it was probably left in one
spot for the parting off), so the bed was in excellent condition. All
things considered, that was very good for me, as the cross-feed
leadscrew and nut were a *lot* cheaper to replace than the longitudinal
leadscrew and the half-nuts.
I suspect that your 5914 had seen a similar life, and there may
be somewhere around a bed turret for it with a matching serial number
(as mine was).
I bought the new nut for about $50, cut the screw
thread off of the lead screw asm and silver soldered a new length of
acme screw stock onto the remaining stub of the lead screw. Alignment
was not perfect so I ended up laying the asm on a steel table and
giving it a few loving taps w/ a copper or brass mallet. I got the
idea for only replacing the threaded portion her on this news group
about 3 years ago (just as I was beginning to repair this machine). I
still had my mid 1920's vintage South Bend lathe to turn the ends of
the acme threaded stock and the stub end of the original lead screw. I
bought a 3 or 6 ft long stick of precision acme screw stock from
McMaster Carr.
I've still got the old leadscrew, and I will probably use it as
a guide to cut a new leadscrew for the future. I've got the acme
threading tooling for 10 TPI ACME LH, and the follower rest, so I should
be able to do it.
And -- I have the 10 TPI Acme LH tap for making a spare nut.
I should make both before I need them again. :-)
Enjoy,
DoN.
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