On Thu, 1 Dec 2016 09:29:12 -0800 (PST), TimR
wrote:

Followup question:

I have to cut through plaster and metal lath. I guess it's expanded perf metal, from the tiny bit I can see through the faucet openings.

I would cut a hole from stud to stud, but it's a lot harder to find studs in plaster walls, at least for me. I hope the shower is centered between studs.

The web has recommendations for a Rotozip and a utility knife for cutting plaster down to lath. I have both, never tried the zip on plaster though. Or a dremel and a lot of cutoff blades. Anybody have a good way to do this job?

A 4" angle grinder with a diamond blade. It will cut the plaster and
the metal with no problem, clean and fast. If you can borrow or rent
one, it would be great. Wear goggles.

https://www.amazon.com/4-Inch-Angle-Grinder/s?ie=UTF8&page=1&rh=i%3Aaps%2Ck%3A4%20Inch%20Angle %20Grinder