OK, trying to make a 2" diam. pocket, 4" deep, in the some thick concrete for a railing post. Going to use a 2" diamond core drill, but then how to hollow out the rest? My initial thought was to then drill out the center with a 1" or smaller bit, as I was going to drill all the way through the slab for a drain hole (the railing is only used intermittently). Then either keep drilling with even smaller bits and/or start chipping away with a cold chisel.
Can't seem to find a solid 2" diam. milling/grinding bit. Any other tricks?