Just did a bunch of cut ins through plaster on top of button board (drywall with holes all over it). Total wall thickness of 1 inch.
I used the 1/4 inch zip bit for plaster I think. I tried the 1/8 inch and burned up in no time. It has the knurling on the business end. I went through the plaster first, then extended the bit to get through the drywall. It is a lot easier on the bit that way. My helper stands with the shop vac to follow the roto zip. Not much mess.
