I'm a relative newby to turning and have a problem for which I don't see an easy solution.
I've just turned a bowl which is 6 1/2" in diameter but with a 4" opening. The bowl is finished and it is now time to part off the tenon/spigot. My problem is that my OneWay 4-jaw chuck doesn't open wide enough to hold the bowl by its opening, and the Jumbo Jaws don't close small enough to hold it by the opening. The outside from the opening on top to the sides is too high to be caught by the rubber jaws on the outside.
What is a reasonable solution? Some sort of jam chuck on a spur and hold the tenon by the tail stock while I part it off?
I have run into the same problem. That's when I dust off my original reversing "chuck" that I thought I would never use again when I bought a set of cole jaws.
I made it of two plywood discs about 12 inches in diameter. The first is mounted on a faceplate, turne round on the lathe and padded on the surface with non-skid carpet underpad. The second disk is attached to the first with three stove bolts and wing nuts equally spaced around the perimeter. The second disk has a hole in it to fit around the base of the bowl (actually I made three different ones with different diameter holes) so that the tenon or chuck recess can be finished off. I stapled a piece of the carpet pad to the inside of this disk and made radial cuts in it so the shoulder that presses against the bowl is protected. This hole is also tapered, being larger inside where the bowl sits.
To use, just invert the bowl on the solid disk, seat the second disk over the base of the bowl and tighten the three wing nuts equally to clamp the bowl. I also found it convenient to have sets of different bolt lengths for different bowl heights. Put the wing nuts on the side toward the headstock to keep them out of your fingers while spinning.
Hello. Use your chuck to turn a jam chuck held in a mortise that will wedge into the opening in your bowl. Alternative is to make a larger one and wedge the bowl into the opening in the jam chuck.
Or turn a hollow ring and hot glue the four sections you cut it into onto the jaws, or use double-stick tape. Then chuck up.
Next time consider a mortise that doesn't have to be re-turned.
You could do that- though what I've tended to do in the same situation is either to scoot the tenon forward in the chuck enough to part it off, or to take it off the lathe entirely and saw off the tenon with a handsaw. The second solution requires a lot of sanding, but sometimes that's the way it works out best.
Welcome to woodturning. The San Diego Woodturners came up with just the tool to handle the situation that you describe. Actually, it was designed for hollow forms, but it will work very well for your case. I hope I can describe it with just words (here is where a picture is worth a thousand words). Basically, they have a shaft with a Morse Taper No. 2 on one end to fit into the headstock Morse Taper. The other end of the shaft has a 1/4" hole drilled in the center to accept the shank of a sanding pad designed for use in a drill motor. A tapered cone has a hole in the center that is the diameter of this shaft. It is slipped onto the shaft and has a hole drilled and tapped for a set screw that allows it to be secured in place on the shaft.
Now, once this is made if can be used over and over again. The cone must be larger than the hole in the rim of your bowl or hollow form and not so long that it bottoms out on your bowl. Slip the bowl over the sanding pad until it bottoms out in the bowl, bring up the tailstock to hold the bowl in place, move the cone into the top of the bowl to center the bowl and lock it in place with the set screw.
Now, turn the foot, except for a small cone where the tail center is located. After removing the bowl from the mounting, remove the little nub with a knife or chisel and sand smooth.
The San Diego Woodturners version was a steel shaft and a plastic cone, but I've made them out of wood with good results. It takes a little time to make it up, but it will be worth it in the long run when you turn other items with small openings.
Incidentally, my 2003 book "A Guide to Work-Holding on the Lathe" and my new book "The Woodturners FAQ Book" should be useful items to have in your library. They were both designed for the beginner to intermediate woodturner. The new book will not likely be available until the latter part of this month. Both books are listed on Amazon.com. While being commercial, I should mention my magazine, "More Woodturning". You can see a sample of it at my website.
Yes George a jam chuck. But an easy one to do, put on the jumbo jaws, and hold a large piece of wood, turn a shoulder on it so your bowl opening fits on it, put your bowl on it and hold it there with you're tailstock's live center, turn the foot down all but the least thin piece in the center, that you can cut with a knife or chisel after.
InspirePoint website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.