On Apr 27, 8:44*pm, "DoN. Nichols" wrote:
On 2010-04-27, steamer wrote:

* *--I've got a 5" Buck6-jawon my Myford Super 7. Had to make a
backplate as none were available but worth every bit of heartache to get it
done. If Buck makes achucksmall enough to fit your lathe go for it. Nice
thing about the6-jaw: you can leave one jaw out, if necessary, to
accomodate lumpy castings, etc but the full 6 gives you the ability to grip
relatively small stuff: 3-jaw chucks tend to have fairly blunt gripping ends
but the6-jawvariety are much pointier, so to speak.

* * * * Also -- another significant advantage to a6-jawis that when
clamping thin-walled tubing the6-jawintroduces less deflection than
the 3-jaw does.

* * * * However -- a benefit for the 3-jaw. *With an irregular surface
on the workpiece, a 3-jaw *always* gets full contact with each jaw.
(3-points are self centering). *With6-jaw, it is likely that one or
more of the jaws will not be making proper contact, reducing it in
effect to a 3-jaw with skinnier points.

* * * * And for either 3 or6 jaw-- if thechuckhas a separate
backplate, it is possible to make a spacer with some other features to
turn it into an Adjust-Tru (or any of a number of other trademarked
names, depending on the maker of thechuck. :-)

* * * * First -- you turn a recess in the center of the mounting plate,
and mount a round piece of steel in that, with several countersunk
bolts. *Best if it is a good tight fit in the recess so it can't shift
in there.

* * * * Then -- turn up a spacer ring to go between thechuckbody and
the backplate. *Drill and countersink it for bolts to attach it to thechuckbody which go into the threaded holes which the backplate normally
bolts to.

* * * * Drill and tap four radial holes at 90 degree intervals around
the ring for setscrews to press on the original round piece of steel.

* * * * Then drill and tap holes in the ring to match the holes in the
backplate, enlarge the backplate holes (and countersinks if present) a
bit to allow motion, and attach the ring to the backplate with these.

* * * * In use -- loosen the backplate bolts to finger tight, and use
the radial setscrews to shift thechuckto true (relative to the
backplate) for the workpiece size in use at the moment, and snug the
backplate bolts and re-check the centering. *If it is still on center,
snug them down firmly and triple check the centering. *You are now ready
to turn.

* * * * Enjoy,
* * * * * * * * 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 ---

All this talk of a 6-jaw has me thinking.

I have an opportunity to pick up a 4-1/2" "self-centering", plain back
6-jaw chuck, as opposed to the independent 5" plain back 4-jaw chuck I
was considering.

I'm not sure of the maximum gripping size of the 6-jaw, but it's
through bore is 32mm, which is 2mm larger than the 5" chuck, which can
grip up to 4.92".

So I'm wondering if I could make adapter plates so I can use it with
my lathe and my rotary table if needed.

I have read that one can remove three jaws if needed and also that it
was possible to turn squares with the 6-jaw if chucked properly. I
don't know how true any of this is, but I'm really interested in what
you said about making a spacer with some other features to turn it
into an "Adjust-Tru". :-)

Thanks.

Darren Harris
Staten Island, New York.