Need help turning a base

[joemac]

I am turning my first base. It is 4" round and about 3/4" thick. I cut it "round" on a bandsaw then used a Coles chuck to flatten what will be the bottom and create a slight hollow so I can turn it around and mount it on a chuck with expanding jaws which will go inside that hollow I made. My question is, how deep should that hollow be so I can get a grip on it with expanding jaws?

[SceneryMaker]

I make my recesses slightly shallower than the length of the jaws. The tip of the jaw should bottom out in the work.

[MichaelMouse]

I am turning my first base. It is 4" round and about 3/4" thick. I cut it "round" on a bandsaw then used a Coles chuck to flatten what will be the bottom and create a slight hollow so I can turn it around and mount it on a chuck with expanding jaws which will go inside that hollow I made. My question is, how deep should that hollow be so I can get a grip on it with expanding jaws?

Do not go too deep if you're using dovetail jaws, but try to match the opening size to the first point of circularity - small.  Eighth of an inch, maybe. See my post to the chuck advise thread for example. Depends on your downhill skills and the design you're after.  A "first" suggests K I S S edge, so remember to cut downhill, and snub the tailstock up to protect against a snag.

Your Cole Jaws are not, in my opinion, the right start.  Pin jaws/chuck if deep, are much easier to work with, and no second mount necessary, depending on design.

[Arlin Eastman]

What both of them said.  It does not need to be deep just enough to grip and let the wood seat properly against the jaws.

I have made mine from 1/8" to 3/8" but it was depending on how big and material I was turning.

I can not wait to see what you are working on.