On 2008-07-16, Bob Engelhardt wrote:
DoN. Nichols wrote:
... The nut was worn too -- but not nearly as much as the leadscrew.

!!! That's not good - it would be much better to have to replace the
nut than the lead screw. Or do you suppose that the nut had already
been replaced, perhaps more than once?

I suspect the nut was replaced many times.

This lathe came with a matching serial number bed turret and no
tailstock, and I believe that the longitudinal feed was almost never
used (the threading dial was in a drawer, and showed no signs of ever
being mounted), and that all threading was done using Geometric die
heads (or the like) in the turret.

However -- the cross-feed was used for parting off work
regularly, so I suspect that it had been through several nuts on that
one leadscrew. Nobody cared that the dial was not accurate, because
nothing was being turned to diameter with it. The precision turning was
done with box tools in the turret, so they just tossed in a new nut (the
cheapest part) to keep it working at the parting function.

I had to chase down a tailstock for normal use, though I do use
the turret for production runs of certain parts from time to time.

If not, do you suppose that the nut being softer had picked up steel
dust & had acted as a lap on the screw?

The nut (being bronze not brass) is not *that* much softer than
the mild steel of the leadscrew. I suspect that the lubing of the
leadscrew and nut was ignored more than the rest of the lathe, because
the lube point tends to get buried under chips.

Is this normal?

In a turret lathe used for production -- I think so. The next
replacement would probably have needed a new leadscrew as well even for
that function.

But the compound leadscrew has very little wear or backlash,
because that was ignored most of the time.

Enjoy,
DoN.

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