I would not use a diamond disc, just a normal abrasive disc will do, I cannot see where the elf's will come into the act, unless its to do the sweeping up 'cos the disc's do make a fair bit of dust
Unguided, my ex sil, told me not to swear at her, I was sitting on the joists on the ground floor notching the joists with a circular saw, when she stuck her nose in and screamed at me about the noise, I looked up to see if she was OK, the saw bound in the timber kicked back and landed in my lap, so she got a right royal mouthful from me, stupid cow wanted me not to make a noise, and it was a freebe for her as well, friends you can choose relations you are stuck with