On Fri, 09 Sep 2011 17:10:03 -0500, "Lloyd E. Sponenburgh"
lloydspinsidemindspring.com wrote:

" fired this volley in news:65cf7d1e-
:

You can adjust a three jaw once and
then machine a hundred parts without having to spend that 2-3 minutes
per part.


You can do that with a 4-jaw, too. If you torque all 4 jaws to the same
torque, only loosen two jaws, are using the same o.d. workpiece each
time, and re-tighten those two jaws to the same torque as before, it's
every bit as true as a scroll chuck would be.

It's in the maneuver, not the hardware.

Besides, only collets are accurate on every chuck-up.


LLoyd
Greetings LLoyd,
With a 4 jaw you at least need to tighten two jaws. With a three jaw
only 1. And accurate 3 jaw chucks will repeat better than .0005". If
it was true that the time difference was practically nil then
everybody would use 4 jaws almost as much as 3 jaws. But for even a
few parts a good 3 jaw is significantly faster than a good 4 jaw.
Eric