I did a little project on my benchtop lathe. This is a Craftsman 109.21270 lathe dating back to the 1950's. Thanks to Paul, who gifted this lathe to me a few years back, and my friend Shane who helped me with the machining as part of the restoration.

It's a very light duty lathe, but it is possible to do some small-scale precision work. Here, I was shooting for a finished diameter of .344. Close enough. :-)

I hand filed the end into a hemisphere.

After parting it off (hacksaw), flipping it around, and turning a small stub on the back side, I soldered the stub into a piece of brass tubing to serve as a handle.

The goal of all this is to use silicone sealant to form radii in the corners of the form.

I used the little spherical tool to smooth out the beads of sealant so that they had the correct radius. Hopefully when I do the layup, the outside edges will have this same radius...which matches the outside bend radii of the center arm rest.