Grigg, you nailed it! I made two guide pieces, one with the diameter of the tap drill (Letter drill "W" for 7/16X20) and another one to guide the tap, with a 29/64" hole in it. I made mine with a few thousandths' clearance over an unworn crank snout, 1.152" diameter. On a worn crank, wrap a layer or two of masking tape around the crank to take up any slop. You'll need to remove the Woodruff key from the crankshaft, or broach a slot in the guide to accomodate the key. It's easier to remove it, unless you're trying to do it with the timing cover in place. My drill guide also aligns itself in the front oil seal, but I really don't plan to attempt a drill/tap job with the timing cover on!
I use Kasenit case-hardening compound, same stuff I use in my gunsmithing, to harden the fixtures. Coming soon- - - - -a harmonic balancer pusher that works with the old style balancer with the hand-crank lugs!
Jerry
