Here is the setup for boring the holes in the crank webs. The screws to hold the crossbars on were added, as was a brass weight plus some stick on wheel weights to balance it all. Started with drilling a hole through the webs - there is one pair of webs in the fixture, they are all number stamped to keep the pairs together from now on.
Then bored out the hole to size. The first hole is the outer end for the crank pin, i'm taking these to 1/2" diameter. The crank pins are 3/4" OD, and I'll turn a post on either end to fit these holes. The shoulder that leaves will serve to set the spacing between the two webs.
First pair with crank pin hole done
and the rest with first hole done
I cut a short length of 1/2" rod to use as an alignment tool, short enough not to stick out either side. This will ensure that the two holes in each pair line up properly
With the short rod in the hole, the pair was run into the fixture to drill/bore the crankshaft hole. You can just see the short rod behind the cross bar
Drilled and bored the crankshaft hole to 3/4"
The final passes were light cuts to sneak up on the close fit on the shaft, I'm using a piece of the shaft material as a gauge:
Taken out of the fixture, thats one pair of webs with the holes done. The ends of the webs still need to get rounded off, both concentric to the crankshaft. This is not the final spacing of the webs, the upper pin is too short to reach if I move the webs farther apart. Final spacing is about double this.
As you can see better here, the crankshaft hole gets close to the edges of the web. To join them later, I'll use loctite retaining compound first to get them positioned, wait for that to cure, then put in taper pins. I am figuring two pins at each shaft, one from the end, the other crosswise. The webs are thick enough to let the pins be spaced along the shaft axis.
So, three more crankshaft holes to bore!