Cole Jaw Jigs
I did not like the way the 6 sided bowl clamped onto the chuck plate that was set up with 4 jaws. So I made my own version of a clamp to use to hold these bowl blanks onto the chuck. They seem to be a lot more secure than the rubber pins that came with the chuck.
I drew up a pattern to make these to fit the metric bolts that fit the threads in the chuck plates. ( PDF of pattern ) Then I cut these from 1/2" BB plywood on the scrollsaw. I cut the clamps across the rounded top and hole with the table at 90 degrees leaving the bottom uncut. Then I used a bowl blank to set the bevel for the final side of the clamps as you can see from the pictures.
The clamps installed on the chuck on the lathe.
I have used the end of the tool rest to line up the sides of the bowl blank to get it centered on the chuck.
I turned a cone to help center the blanks onto the cole chuck plates. First I turned a cone to put into the tailstock that helps me center the blank. Just hold the blank loosely on the chuck face and turn the chuck a few turns to get the bowl centered. Then I start bolting the plywood clamps snug around the bowl, tighten them down as you snug them up against the bowl. When all 4 clamps are tight I snug it all down using the chuck key in the chuck as normally tightened. I also use the clamps on the inside of the blanks when they are too big to fit on the outside. Then I have a set that are rounded to fit the outside of the bowl when I reverse chuck to turn the final bottom. Note that all of these are beveled to fit the angle of the bowl slope. Here is a PDF file for the main shapes of the jigs, you cut the final side to fit the angle of your bowl.
After throwing a few bowls off the cole jaws I tried a donut chuck on the cole jaws. I made a drawing with the slots at every 45 degree, but the slots are not spaced that distance on the chuck. Anyway I can use 4 bolts to hold the donut on, and since the bowl is actually held in the regular jaws of the cole I think the 4 bolts on the donut are going to work just fine.
Secure the bowl in the cole chuck as you normally would . Then put the ring on as just a saftey. I only use these on those bowls that have been turned thin and I do not want to apply too much grip with the cole and risk crushing the bowl. I use bolts and wing nuts that went through the holes in the cole jaw plates because I could not find the right thread size bolts long enough at the local hardware store. Since this donut is just a saftey ring I don't think it needs to be any better secured than I have it now. Here is a PDF of the donut, it is 11 X 17 paper but there are programs that you can print it in sections.