I would like to cast about 25 parts roughly 3.5 x 3.5 x 3 inches tall.
Normally EG would seem like a good target material, but it would be really handy if, after casting, it can be at least drilled, and maybe even tapped.
It will be very difficult (not completely impossible, but difficult) to place an insert into the part prior to casting, so it pretty much has to be filled with something that can be hand drilled.
My prior reading in the "big thread" indicates that it is difficult to drill through normal EG, as one would expect, due to the hardness of the aggregate.
Would something like an Al powder or other filler option be viable ?