A week or so back I posted the end results of my venture into making new chisel handles for my old socket chisels here. With the promise that I would show the method I used. So here is the method I used in making new socket chisel handles with octagonal flats.
I made a template to mark out the lengths I needed. I found it easier to get repeatability with a flat template than by holding the model handle up to the blank on the lathe.
I then use calipers and a pencil to determine the diameters and depth of the socket needs a matching tenon.
Use the pencil eraser end, not the pointy end to determine the depth.
I used a card scarper to cut four flats which, on a circle, comes real close to approximating an octagon … more comfortable than an octagon too.
Once the flats were cut, I put it back on the lathe to sand, burnish and finish with shellac.
After cutting off the nubs on each end (is there a turning word for the end pieces that go to scrap on the end of a spindle?) with a flush cut saw, I use a file to fine tune the fit of the tenon into the socket.
Wipe sweat from brow, repeat until all handles are done.
More details and tips can be found in the source: Making chisel handles
-- Galootish log blog, http://www.timberframe-tools.com