Pete C. wrote:


asdfasdf wrote:

I have a 10" South Bend lathe (serial RKL) that I'm
having a problem with. I've used it to turn small
pieces until now. I was making a shaft about 5.25"
long and .75 diameter. I kept checking the diameter
and was satisfied at the tailstock end but found that
headstock end was about .008" larger. I am not
using the tailstock so alignment to the tailstock
is not an issue. I have to assume that the headstock
is not aligned with the bed. Does anyone know the
correct procedure to re-align the headstock with the
bed for the given lathe?

The shaft was probably flexing since you were not supporting it with the
tailstock.
Nope, workpiece deflection would make the free end bigger, the headstock end
smaller. On most lathes the headstock cannot be adjusted, it has
vee ways on the bottom that fit to the bed ways.

The remaining possible problems could be wear on the bed or twist of
the bed. Wear of the front way near the headstock would cause the
larger diameter near the headstock, and that is a bit difficult to fix.
Twist in the bed could go either way. What you need to do is find
a piece of hardened and ground shafting, or something stiff and round,
and put it in the chuck. Use a dial test indicator and read at several
positions from close to the chuck to about a foot away. Rotate the chuck
slowly by hand and average the high and low readings to eliminate
wobble from the measurement.

Now, you can shim under the tailstock end of the bed (assuming it is a
bench lathe) or otherwise adjust feet on the cabinet to see if you can
reduce the error. You may be able to find a compromise that even partly
nulls out the effects of wear.

Jon