I just sent an email off to Hal asking questions on some of my progress, and I realized I had taken some pics that I had not posted. I built a jig to cove the arms; it is designed to hold the arm billets in place with three threaded rods, and to hold the jig at an angle to the saw blade. Here are pics:
This shows the jig in action on the table saw. The square frame holds the billet in place with three rods. the rods are epoxyed into wood handles and run through threaded inserts screwed into the frame. The frame has a triangle attached to the side to set the angle to the saw blade. That way I just instal a fence perpendicular to the blade and the jig takes care of the rest.
This shows what the cove cutting jig does from below. I make multiple passes over the blade, raising it each time a quarter turn. The blade cuts a cove on the bottom of the billet (installed upside down, so the cove is on top where your arm rests) as well as through the jig. There is a small 5/16 shim glued to the end of the billet to raise it up and give the cove cut a taper.
One corner of the jig has a triangle piece of wood glued into the corner. This is to make sure you instal the billets correctly for the right and left arm. A corrosponding notch is cut in the corner of each billet. I managed to glue the shim on the wrong side of the billet, but fortunatly the notch prevented me from cove cutting the wrong side…
This is the result on both arms.
I have fallen in love with the threaded inserts used to hold the threaded rod and the handle on this jig. They are going to be featured in future posts for fine adjustment of more jigs!