For a quick check, put a drive center in the head stock and a center in the
tail stock. Move the tailstock center up to almost touching the drive
center and observe any misalighment. It will generally be horizontal rather
than vertical misalignment. If the centers don't align by more than a
1/32", loosen the bolts that fasten to lathe to the stand it is sitting on.
Presumably the points will come into alignment, or certainly improve from
where it was. Now, tighten one bolt at a time while observing any movement
of the centers. It is likely that one pad/foot on the lathe will not be
touching the mounting surface when the points are in alignmnet and you will
have to come up with a suitable shim, preferably metal, to put under that
pad so the bolt can be tightened down. This process should take well less
than an hour and will probably resolve your problem.
If, on the otherhand, the misalignment is vertical, you have another set
of problems that I can't help with.
"Alan" wrote in message
...
I have read in several posts that cast iron beds can twist if the
lathe is not correctly "set up" in a level and "true" fashion.

I know my gap bed lathe isn't excatly "true" when I move the
tailstock centre up to a drive centre. It has a 4 foot cast iron ways
(including an 8" gap) and a fixed headstock. The headstock shows no
sign of ever having moved from its original position and the tailstock
is certainly too solid to have deformed in any way. There is no
adjustment on the tailstock to permit it to be adjusted sideways.

When I set up the lathe about a year ago, I endeavoured to eliminate
any rocking by the use of shims under the legs of the stand, though
did not use a level to pack it horizontal side to side and front to
back.

Could a bed of this length be out of allignment as a result of a poor
set up? I suppose I assumed the cast Iron bed would not deform and
hence perhaps didn't spend the necessary time when I first set it in
place.

Many thanks,
Alan