I need to mount some 4" house numbers on a concrete wall (drilling 3/16" holes for studs extending from the numbers). Normally when I drill into concrete, it's hard to get a hole in an exact location (even using a center punch to force the bit to start in the right place). I assume it has to do with the hammer action of the drill and aggregate within the concrete making the bit want to go slightly off center, but usually the final hole is a tiny bit (a few mm?) off from where I originally marked.
This is usually fine since whatever I'm mounting doesn't need to be in an exact position, but with small house numbers, one of the holes being a little off will mean the studs won't fit in right or the numbers will be a little tilted or not aligned right. Is there any tool or technique to help accurately drill holes in precise locations in concrete?