On 2009-06-28, David Billington wrote:
Michael Koblic wrote:
I just got a 3-jaw chuck fo my Taig lathe. It comes with two Tommy (?) bars,
a hex key, a washer and a set of instructions. The jaws are aluminium and
unfinished, the instructions tell you how to turn the jaws true.
[ ... ]
Not sure about the construction of the TAIG chuck and how it operates
given the mention of a tommy bar and looking at the TAIG site but all
the 3 jaw self centering chucks I have are marked with a master pinion
which gives the least run-out when used.
No pinions on the Taig 3-jaw. The scroll plate is bare on the
back of the chuck, with three holes for Tommy bars drilled in its edge
for tommy bars. The chuck body (thin compared to one for pinions) may
also have three holes for Tommy bars. (Mine is an old one, and does not
have the holes in the body, so I have to grip the jaws. :-)
The chucks I have all have 3
pinions which operate the scroll and one produces the least run-out. As
the TAIG is a scroll chuck, from what I read, then if you have more than
one hole for the tommy bar to tighten the chuck, then maybe you want to
mark and always use the same hole to ensure consistancy, that may
improve you run-out.
Actually -- the closest approximation of the "same pinion" in
the Taig is the same hole in the chuck body. The scroll plate should
use the nearest hole approaching the master hole in the body to maintain
an approximation of the same pinion effect.
The chuck has two-piece jaws, with the master jaws being
hardened, and captive unless you remove the snap-ring and scroll plate
(which should be avoided unless necessary). The top jaws are
aluminum, with a groove to maintain alignment with the master jaws, but
without a cross-groove to maintain the position of the soft jaws along
the master. They depend on the fit of the screws which secure the top
jaws and nothing else.
Maybe also tighten using different tommy bar holes
and see which produce the least run-out.
Yes -- pay particular attention to which tommy bar hole in the
body gives the most consistent runout. It will be more sensitive to
that than to the tommy-bar hole in the scroll plate.
Enjoy,
DoN.
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