"Jam" Chucks Example

[Don Stephan]

No idea what gave me the idea, but I made one, sometimes two "jam" chucks for each of my jaw sets. They are nothing more than a 3/4" plywood disc with a shallow tenon, yellow glue, and a 2" high density insulating styrofoam trued with a spindle gouge after the glue dried. For any of my once turned bowls, I can mount the bowl in the four jaw chuck using the bottom tenon and sand the inside and rim with the first grit (often 80 or 100); exchange the bowl for the corresponding jam chuck, mount the inside of the bowl over the styrofoam, bring up the tailstock, and sand the outside with the first grit; sand the outside with the next grit and reverse the bowl to sand the inside with the second grit, and so on. (The two wood cylinders in front I also use as jam chucks, there is a layer of leather on the end to project the surface of the bowl.) I have never found the styrofoam to mar the surface of a bowl sanded to 220/240 grit.

 

[Brian Gustin]

Technically, friction drives - I have dozens of scrap wood blocks with tenons in various diameters and profiles that I use for the same purpose.

Technically, a Jam chuck is just that - a piece of wood or material on which your project is "jammed" and held in place in its own right with little to no tailstock support, so your method (and mine) are better termed as Friction drives.... (for the purists on the boards that might insist on corrections.. but to them I say, It's a LOT less typing to just call it a Jam Chuck!)

I use some cheap jar opener helper pads as padding for my friction drives for items where I used a Tenon (so I can turn away the tenon when project is complete) Styrofoam would probably work equally as well (if I had any laying around I'd probably use it - I won't go out and buy some when I can use scrap wood for the same purpose)

 

[John K Jordan]

Those are quite useful, yours look great. Beats turning a wooden jam chuck for each specific bowl (although sometimes that's better).

Some people put the "puck" on extensions to reach deep inside when reversing a large bowl or a deep vase/form, holding the extension in a chuck. I've used a fat cylinder with a tenon held in a chuck and a piece of rubber on the end (I've heard of people using a piece of mouse pad)

 

[Kent Reisdorph]

I've used the web-type rubber drawer liner. That worked OK, but it tends to break up after use. My go-to is a wooden jam chuck with 3M white scratch pad for the buffer.

 

[Dave Bunge]

Neat idea. How did you turn the styrofoam once it was attached?

My experience cutting sheets with a utility knife is that it's very prone to catching and tearing. Probably my utility knife was not the sharpest most of the time.

 

[hockenbery]

@Don Stephan friction drives look good
If the foam is really stiff I’d use them

With vacuum chuck and friction drive you want a padding that
gives just a little to make the vacuum seal or accommodate any slight mismatch with the friction drive surface
The padding should not mar the work or leave color transfer.
Lastly the padding should not be spongy and allow the piece to move if any pressure is applied to the surface while turning.

I often just use a paper towel pad to cover wooden friction drives - has all the needed properties.
One paper towel can do a 1/2 dozen bowls before it gets dirty or worn

 

[John K Jordan]

My experience cutting sheets with a utility knife is that it's very prone to catching and tearing. Probably my utility knife was not the sharpest most of the time.

I've found that a sharp, thin, fillet knife handy in the shop for cutting a variety of things.

One thing I use it for is cutting sections off a roll of paper shop towels. I usually only need a small piece and hate to tear ragged pieces from bigger sheets. I'm pathologically messy in so many other ways perhaps this is a desperate grasp for some token of order...
On the wall behind the lathe.


JKJ