Nathan: If it was mine, which it isn't cause I have Cleavlands
and was sick of constantly having to fix it, this is what I'd do.
Welding may anneal the casting to a soft state so it's a last resort. I'd get some bronze plate and shape it to replace the phonolic you have now Drill and tap a 6-8/32 depending on room in the center of the insert and web of the arm and countersink it in to about 50% thickness of the bronze. Bond with 680 Loctite as well. I don't think the heat in this area is hot enough to detach it. Keep the fits tight as possible. The other more aircraftish method would be to shape the arm lips and bronze for a dovetail joint for mechanical attachment. More time and a milling machine is needed for this one. Some of the older craftsmen are skilled enough with files to be able to do this as well.
Now for the icing on the cake. Take the cam and get about .002 hard chrome on it. This is cheap to do and wear will stop completely.
WARNING........ Bake cams at 400 degrees for a couple of hours before using them to let the hydrogen escape. The cam will be brittle if you don't do this. As time goes on, any residual will come out naturally. They plater may take care of this problem if you ask. Don't mention it's for an aircaft or they may not even plate it for you
Ron
Before you believe anything I say, check with two more people. If they agree, I must be right.
Still there and still cracked, annual inspection is do this month. So I'll take care of it this weekend. I should have listened!