"res055a5" wrote in message
news:69zFd.7070$C.3427@trnddc05...
got it !
thanks guys for the advice...it's a little late for the piece i have on
the
lathe,
but now i know what to do in the future.

there is a set of 3 jaws on ebay for sale for nova chucks...and i'm
wondering
whether the spigot jaws would be useful for turning goblets?
rich


That's yes and no.

They certainly offer you a greater grip length parallel to the axis of
rotation to resist the outward forces of hollowing on an end grain piece,
but they are a bear to use to rechuck a piece without losing concentricity,
because they, almost of necessity, distort the wood of the spigot (tenon)
with their serrations. It's almost impossible to get back to the status quo
ante with them if you for some reason dismount the piece, or if turning a
green piece which you leave to dry long enough for it to become oval. Some
people might even get a catch that compresses the wood of the spigot!

I hedge my bets when using them (35mm) by mounting a centering cone (I have
a number premade) on the Nova live center, which offers that opportunity. I
use it to hold things in the proper relationship while trying to reestablish
the contact between the nose of the jaws and the shoulder of the tenon.

I got the power Grip jaws with my Super Nova, and the external dovetail has
done for pieces hanging out 14 inches from the chuck, but you have to start
with a substantial piece of stock to make the dovetail spigot. With the
steady, the 50mm jaws, gripping outside, have proven adequate for the way I
cut.