Centering a piece that is too short to get a good grip in the 3 jaw can take way too long.
For the Sherline it needed to be small unlike our friend from the Cookbook. I have used the little bearings from my router bits in the past; they seem to be a great size for smaller work and are readily available.
These little guys are 1/2" x 3/16, I found a little shoulder bolt, made some modifications to it and mounted onto a 1/4 square piece of stock. After is was all assembled I bent the end up until the bearing was on CL with the lathe axis. A cool 45min. project.
