granite tile mounting plug - 5 mm hole, M3 thread

How do you mount a printer to a granite tile? Well, with brackets, of course - see https://www.thingiverse.com/thing:2859409. But how do you get the screws into the plate? The default would be to drill a hole, stuff in a nylon plug and put in a wood screw.

But: after drilling these holes, I had four large craters at the back of my tile (ok, I had expected something like that), and didn't want to risk breaking it completely by using expansion plugs. Next best option would have been to cement