On 2010-04-25, Searcher7 wrote:
I have a mini-lathe, but even for those with the larger machines I was
looking for opinions on whether or not the "Adjust Tru" feature on
something like the Bison is really worth the money.

Is any gain is speed or possible accuracy really worth the cost that
these go for?

Which chuck -- a standard 3-jaw chuck, or a collet chuck?

For the former -- it will only be true at the one size which you
adjusted it for -- and only as long as you use the same key hole
(ideally the one marked '0' or something similar) for tightening it.

The adjust-tru can tune out errors in the chuck, but the scroll
plate can have a sensitivity to where it is in its cycle. So tune it
for true in one position, and it will be fine there, but have varying
degrees of error at other workpiece diameters. (It will be right on for
sizes larger and smaller than where you tuned it which are precisely an
integer number of jaw teeth larger or smaller -- because the scroll
plate will have turned precisely an integer number of turns and it will
be back where it was.

With a good *new* chuck, there should be little error. If it is
used, the scroll plate will have varying amounts of wear in different
rotational positions.

If you are doing a lot of work with the same size stock, and if
your finish diameter is barely smaller than the raw stock, then this
could save you time.

But -- you could also get the chuck with two-piece jaws, and get
some soft jaws which you can bore to a precise fit for that stock
diameter. That will probably cost you less than the adjust-tru feature.

And if you will always be making parts from stock with is not
just barely larger than the desired finish diameter (of the largest
part), you can just chuck up the stock, turn to the desired diameter,
and finish all the other work before you release it from the chuck.
Don't expect to turn the workpiece around in the chuck and finish the
other end to precisely the same surface unless you take the time to use
the adjust-tru to truly center the workpiece on an exposed area which
has already been turned. It is easier to turn workpieces around if you
are turning between centers instead of held in a chuck.

If, instead, you have a collet chuck (which Bison also makes) you
can use the adjust-tru to get the collet running truly on center and
will be able to exchange collets with very little error -- given good
collets.

Good Luck,
DoN.

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