On 2010-01-18, Royston Vasey wrote:
I stumbled across this website

Which website? Did you find a web site which mirrors this
usenet newsgroup rec.crafts.metalworking? Normally, there are (and
should be) no images here.

and the pics of the "pie jaw chucks". I did a
little googling around and generally understand their benefits.

Do you machine the gripping bore to suit the work?

It depends. There are "soft" pie jaws which can be machined to
fit a specific workpiece. But there are also hard jaws -- multiple
steps which are a precise fit for standard diameters and a pretty good
fit for in between sizes.

Why do the jaws in the pic have the radial profile rather than solid - just
to save material & weight?

Again -- which pic? And what do you mean by "radial profile"?
pie shape of the jaws, or the radiused gripping surface?

The pie shape is so when fitted to a six-jaw chuck, the chuck
can be closed to the maximum amount, allowing the sides of the jaws to
just barely touch.

The radial profile is to fit standard diameters -- and grip
fairly well diameters just a little smaller.

Are what you saw for six-jawed chucks? The combination of the
six jaws and the curved gripping surface allows gripping rings with
minimal distortion compared to the same thin walled object gripped by a
three-jaw chuck.

Enjoy,
DoN.

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