Drilling stone buttons ~ Used a much less expensive bit, rather than a diamond bit. The Hi Power Bit (for metal, wood & plastic) was successful. Stated the larger masonry bit blew out the back and the front hole entries were also messy.
Upcycled lamps from vintage motorcycle and automotive parts by Moto Graphica, Melbourne. Recommend spraying several times with a matte clear coat to prevent rust transfer from old industrial metal items.