For some time I’ve wanted an easier way of reverse mounting a bowl for finishing the bottom, and have seen several options. Seeing that you can build several of these options, I knew that was the route I would take, as I could not justify spending around 100 bucks for a set of jaws.
I’ve considered the Longworth chuck and the donut chuck, but recently I saw some homemade jumbo jaws for a scroll chuck, and thought I could make a set of these for my Talon chuck.
The first thing I did was to cut a square of 3/4″ plywood. My two lathes both have a 12″ swing, so I made the square 11″. Since the Talon chuck has about a 1 1/2″ range of travel, I figured this would give me enough travel to accommodate any size bowl up to around 10″ in compression mode, and up to the full 12″ in expansion.
I laid out cutting and drilling guide lines, first by drawing from corner to corner, then from side midpoints, and then bisecting the resulting 45 degree angles, resulting in 8 guide lines.
I couldn’t find a compass, so I just marked 5 1/2″ from the center down each line, and connected the dots. Then I cut the square into 4 smaller squares on the tablesaw, and rough-cut the corners on the bandsaw.
Next I laid out the mounting holes using a set of jaws to locate the positioning. I then drilled them on the drill press.
I then mounted them on the chuck, and retracted it all the way in. I mounted it on the lathe, and turned the jaws round, and to a diameter that would allow about an inch of travel before hitting the bed. I also turned grooves in the face of the jaws, spaced at 1/2″.
I removed the jaws, and then drilled holes along the pin layout lines, spaced at 1/2″.
Here is a shot of the back of the jaws.
And a shot of the front.
Here are all of the parts of the jaws.
The jaws being attached.
I made the mounting pins by turning a piece of maple down to 7/8″ and drilled a 1/4″ hole in the center, and parted off 1″ lengths. I used 2″ x 1/4″ carriage bolts, and 7/8″ chair foot bumpers to finish the pins.
The correct holes to use is determined by expanding the jaws out an inch, and then placing the bowl centered on the jaws. Here I am using a bowl that I originally turned probably 5 or 6 years ago, but never got the base completed. It was green when I turned it, and has warped considerably.
The pins are attached with washers and nuts on the back of the jaws.
Here’s a shot of the chuck with jaws and pins attached.
The bowl is then mounted in the chuck. Considerable pressure was applied, and it was held very securely.
Here it is mounted on the lathe. The tailstock was used for additional security.
I turned most of the bottom before removing the tailstock. I used my homemade carbide tool for most of the bottom.
I finished the rest of the bottom.
And then sanded and finished it.
Once it was complete, I buffed the entire bowl. It turned out pretty well.