Make sure it's a good weld and finish it neatly. Make a 90 degree bend about 2" from the weld, and another in the opposite direction about 4" from that, to form a crank. (Fig 4) Set  this part aside to cool down. Taking about a 14" length of 3/8" square, forge circular eyes on each  end with a 1" inside diameter. (Takes about 3.1416" of material for each eye.) I like to turn them  opposite to one another, but that's up to you. Align centers with bar. About 2" from each eye, bend at 90 degrees, so that eyes face one another, and everything lines up square. You should now have  something that looks like Fig. 5 and slides onto the main shaft with just enough clearance to allow  the "crank" to revolve smoothly but not sloppily in the support bracket. Insert the crank into the  support bracket, and tack the other ring onto the mandrel with the buzz box with just enough clearance from the bracket to allow everything to rotate smoothly.

    About 1/2" from the second ring,  drill a 3/4" deep X 15/64" dia. hole. File or grind a slight chamfer on one end of a 1 1/4" piece of  1/4"round and press fit it into the hole. The completed revolving mandrel should look like Fig. 6. To use, clamp "U" shaped portion of support bracket into vise - turn c crank.

Mike Dickie
Pennant, Sask. Canada