As I tend to turn about six or eight bowls in a row and then let the finish dry to later finish the bottoms, I decided I needed, or at least wanted, a quick way to do the bottoms. One Way makes a great set of large jaws for my One Way chuck, but the price is beyond me. So I made one. To start with I took a piece of 3/4" plywood about 14" on a side and drew as large a circle as I could on it.
A little geometry and it was divided into 4 quadrants.
A little more geometry and each quadrant was divided into thirds, complete with an easily corrected error
Starting from the center. the trisectors were marked each inch for holes to hold the bowl hold-downs, beginning with the 3 inch mark.
With one of the jaws carefully lined up, holes are marked for drilling.
Then to the bandsaw and the circle and jaws are cut ready for drilling.
After drilling 1/4" holes for the hold-downs and 8mm holes for the jaws, there are four jaws ready to go.
They are mounted to the chuck slides with 8mm machine screws.
And then placed on the bowl lathe. Next for the hold downs.