Harold and Susan Vordos wrote:
"Rob Newman" wrote in message
...
Actually, if you use a good dial indicator with a four jaw chuck,
you can
turn perfectly round stock. (zero runout)
If you do the same thing, you can turn a round post on square
stock(good
for
cam lobes), or elliptical lobes for whatever....
nice thing to have for extra precison... good luck.



Ah!
But not with this one! This is a universal 4 jaw, not an independent
4 jaw.
Very nice for gripping square objects, but inclined to grip only with
three
jaws, or, really, two. The moment you move away from 3 point
contact,
things get more complicated where chucks are concerned, unless they
are
independent. It likely would not perform as well as a three jaw
chuck with
round stock due to the tightest jaws gripping, with the set at 90
degrees
gripping, or not. In a perfect world they make sense. In practice,
they
may not.

Harold

I find a wrapping of paper makes such a chuck grip more reliably.

I refinished a Harbor Freight cheapie four inch four jaw universal
chuck with Clover Compound. It took hours. I removed the scroll and
pushed each jaw through each slot in both directions, both
orientations, using a 1/2 ton arbor press until things started evening
up, then I got the grit out with a toothbrush. Yes, it was so tight it
needed the arbor press; finger pressure wouldn't do it. The work was
intensely boring: press, reverse, press, repeat, count jaws, move to
other slot, count jaws, etc....

Sad, though, you can never get all the grit out. It sure works smoothly
now, but how long will it last? It was for circular milling and hole
pattern drilling on a 20 mm dowel pin, and could use a brass bush for
the dowel pin.

I still have this chuck but we are in extreme cluter mode, not quite a
hoarding situation, and I wonder if I will ever use it. We (Teri and I)
may choose to pay somebody to help us sort out this crunch. We do have
a shredder.

The paper adds elasticity to the grip and can completely remove the
"overcontstrained" condition. Three point contact and all that
kinematic design stuff. I love four jaw self-centering chucks. They
work really well with wood and plastic; no shim is needed because the
work is so elastic.

A modification to a standard four jaw independent chuck is to procure
hex stock or a Balldriver that fits the screws, then drill the interior
to allow this long, skinny tool to adjust two jaws at once. With a
total redesign, you'd have a self-centering independent chuck. With the
mod, you have a quick-centering four jaw chuck. Wups. There goes
another patentable invention. Left and right threaded screws on
opposing jaws....

Yours,

Doug Goncz
Replikon Research
Seven Corners, VA 22044-0394