"Ken Wilson" wrote in message
...
The alternative is the inside holding edge which is not a dovetail but is
parallel and stepped - see
http://www.axminster.co.uk/product-A...Jaws-21941.htm
and then click on the "jaw profiles " bit.

Now - what shape spigot do i make for that? If i understand you i just
cut a straight parallel spigot SHORTER than the total depth of the jaws so
it relies on the shoulder of the wood to be faced flat and not the end of
the wooden spigot - nor do i cut a stepped spigot which i had assumed was
the ultimate profile.

That profile grips outside with a squared shoulder, short enough depth
(length) of spigot as not to bottom against the inside of the jaws, and a
mild undercut of the point where the spigot meets the shoulder ( /spigot\ )
That way the ridge will find the path of least resistance to be snug up
against the shoulder. Help it when tightening with your tailstock.

and would i be better with one of the jaws which has a dovetail on the
inside and out
eg
http://www.axminster.co.uk/product-A...Jaws-21939.htm

or
http://www.axminster.co.uk/product-A...Jaws-22836.htm


(i am off the gripper type jaws after realising the sense of your "chews
up" comments)st.

I like the A&B type. Just got the similar pattern for my Teknatool NOVA
chuck. They call them 75mm, though the minimum seems to be 82 for a recess,
where they work just fine. Joy is in the broad faces on the jaws, which
allows good wide shouldering of relatively small diameter tenons. Did some
green wood goblets with them, and I'm hooked. The spigot jaws are now in
their own box, like the extra sets of 50mm I acquired along with extra chuck
bodies rather than in their compartment in the drawer. I'll be using them
even less than I did before, which was hardly ever.

As to the grip types, there are those out there who swear by them rather
than at them as I do. More suitable to dry wood than green, and they do
grip square stock well. Mine were out of the box for a few ornaments a
month ago for that reason. The O'Donnell type are nice for people who do
wine stoppers, tops and such in a production environment, but my choice
would be http://www.axminster.co.uk/product-A...Jaws-23111.htm
for that type of spigot use and as pin jaws for roughing out. Most useful
type of jaw for general work I own.