Repositioning A Metal Back Box

[NLM1990]

I find myself in a situation where I need to move an existing metal back box up by a few mm and im wondering what's my best route of action is.

I do not want to take an SDS drill to it as I've recently had a new kitchen installed and don't want bits of plaster/stone to cause any damage to the kitchen units.

I'm thinking of cutting out the stone wall with a chisel of some sort but im unsure of the right one to get.

Which type of chisel should I buy to do the job?

 

[gman76]

I would use a scutch chisel.

 

[Taylortwocities]

Properly shield the kithen surfaces with cardboard sheet or dust sheets etc.
Stitch drill the new box location, then use scutch chisel to cut out the final hole.

Or buy a pattress jig