On 2010-05-08, Bill Noble wrote:

The floating holder I have is W.M Zeigler Tool Co, Detroit, no numbers or
model info, 3/4 inch shank is 1.65 long, - the collet is unlike others I've
seen, steel, vaguely like a double angle collet, but with a square base so
it won't turn, and inside, it has a square section to grab the tap. I think
what I have is an early version of the 0-SA variant in the catalog that is
on-line here http://www.scribd.com/doc/7667023/F-...iegler-Catalog -
see page 27 for a good view of the collet - I guess I'll have to be on the
lookout for more collets too

O.K. Once I turned on enough things so it would let me *see*
the catalog. It wanted both JavaScript and Flash turned on to allow me
to see it.

First -- this seems to be overkill for your work, and looks as
though it is for powered spindles, not non-rotating tailstock spindles.

Second -- it corrects for lateral offset, but not for angular
errors such as your drooping tailstock ram. (Assuming that it *is
actually drooping.)

If it *is* drooping, it is wear in the bore in which the ram
moves, and it will droop more the more it is extended.

However, another likely problem is wear on the carriage, so the
whole ram is below center -- whether extended or not.

The fix for the second problem (which can be verified by a Blake
centering indicator or other ways which are less convenient) is to
determine how low it is, and to add shim stock between the tailstock and
the carriage along the parting line which allows for lateral offset.

Most serious lathe makers make the tailstock just a little
*above* center, so as it wears through its life, it will get better
before it starts getting worse.

The Blake is also convenient for tuning the tailstock back on
center horizontally, too.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---