Hi Ron,
Not a direct answer to your query, but an alternative method: I have done the same kind parts for crankshafts, but rather than the square holes I'll do a round one (a little smaller than the shaft so there is a shoulder to help hold things), assembled them with high strength Loctite, then drilled/taper-reamed for a small taper pin that is driven in and cut/filed off flush. Not quite the same look as the square hole would give, but plenty strong and cheaper to do.
Just a thought!Chris