jam chuck for natural edge bowls

[Ben Pierce]

Hi Gang,

I've gotten lots of great ideas on here about techniques for holding bowls on the lathe for finishing the bottom. When using a jam chuck for natural edge bowls, what do y'all do to get it "straight" on the chuck, i.e. to position the foot of the bowl perpendicular to the lathe bed for finish turning?

Ben

[Paul Williams]

I'm sure you will get many techniques that work. What I do is make sure I leave a center mark in the recess or the tenon. I turn the profile of the jam chuck to be fairly close the same profile as the inside bottom of the bowl. Then I use my live center in the tailstock to locate the bowl on the jam chuck. It is never perfectly centered, but it is close enough.

[Thom Sturgill]

Get an adapter that lets you mount the chuck to a morse taper. Mount the bowl still in the chuck in the tail stock. Works great for vacuum chucks, but for a jamb chuck you have to hold it steady while removing the chuck. A center point mark is a better option for jamb chucks.

[John Keeton]

Agree on the center mark for the tailstock, but for the jam chuck, I think you will find that forming a slight "cup" on the face of the jam chuck will provide contact only on the outside perimeter and be much more solid than trying to fit the profile of the curvature at the bottom of the bowl. If you don't get that curvature correct, you will have minimal support. Also, cushion the jam chuck with a piece of drawer liner or some other rubbery material to provide friction and to prevent marring the bowl.

[mike ash]

I do what John just said! +1

[Dennis Ford]

I also do it the way John posted. Only additional suggestion is to use a thin material for a cushion; thick material allows too much movement. I usually use a 3" sanding disk with the grit toward the bowl, any slippage occurs on the hook & loop side and does not mar the bowl.

[hu lowery]

I collect rubber balls of different sizes, fairly stiff ones. With a mark on the center of the tenon to center the foot to be cut away I put a likely sized rubber ball in one of my old disasters that still has a tenon on it and didn't get burned. Stick the junk bowl in the chuck, put the rubber ball between it and the new turning, and tighten down. I could turn some specialty pieces to hold the ball but I never get around to it, just use likely sized junk turnings.

I usually just shove the tailstock in place with hand pressure. The ball is stiff enough to hold the new bowl in place and you can shift it around and the rubber ball will grab in the new position. Worked well until I gave away my ball collection with a little four legged buddy I had to part company with. Now I have to collect balls again.

Hu

[Kyle Iwamoto]

Leave the divot from your live center in the tenon. I never true that part up..... Until I reverse and then I cut it off.

[Ben Pierce]

As usual, you folks have been very helpful. I bought a #2MT adapter for my chuck so I can put it in the tailstock and keep the alignment perfect while sliding the bowl into the jam chuck. BTW, I am using leather on my jam chuck, suede side out, and it holds very well.