Roy Smith wrote:

I've got an idea for mounting a folding extension table off
the back of my table saw which starts with bolting an aluminum
angle to the cast iron top. Do I need to worry about
electrolysis between the aluminum and the cast iron?

Roy...

I've been using the same aluminum [aluminium] insert in my cast
iron table top since 1975 and haven't detected any ill effects.
It's probably something not much worth worrying about.

I recently added an outfeed table to my saw - also starting by
attaching an aluminum angle - that you can look over at
http://www.iedu.com/DeSoto/outfeed.html. It seems to be
surviving fairly well (and will probably outlast me!)

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/solar.html