I am using a diamond core bit to drill tea light holes in granite rock. I am not drilling through the granite, but am making stopped cuts.

I have used a 30mm diamond core bit to make the initial cut. Then used smaller core bits to drill out the core. The bottom of the hole is very rough - bumpy with the smaller core bit marks. I am hoping there is a way to smooth that all out.

How do I smooth out the bottom of the hole?

  • What diameter and how deep are the holes?
    – JACK
    Commented Oct 11, 2020 at 15:24
  • @JACK well my tea lights are about 30mm diameter and 15mm deep so the holes must be a bit larger - otherwise they would not fit.
    – Solar Mike
    Commented Oct 11, 2020 at 15:40
  • @SolarMike That's pretty standard but I've seen some pretty weird stuff on this site.
    – JACK
    Commented Oct 11, 2020 at 18:05
  • Is it necessary to have a smooth bottom? Presumably it is not for aesthetics. Does the roughness of the bottom of the hole affect the installation of the lights?
    – Alaska Man
    Commented Oct 11, 2020 at 21:14

2 Answers 2


So, how rough is the bottom of the hole? Was the hole drilled in steps from small to large or was it a knocked out core.

Some ideas could be rotating wood dowel of a suitable diameter with sand to smooth out the surface. How smooth does it need to be - as long as the tea light sits reasonably square then it should be suitable.

There are low speed grinders designed for finishing holes like that but they can usually be found at stonemasons or marble suppliers - you may consider asking there, but it depends on how big are your pieces and how many for the cost.


I would drill slightly deep and then pour in clear epoxy. Instant polish and level surface.

  • I heartily endorse this option! The only potential drawback is that a clear epoxy may allow the roughness to show through, so a colored epoxy (color chosen to match, compliment or contrast with the granite, at the OP's discretion) would probably be the way to go.
    – FreeMan
    Commented Oct 13, 2020 at 13:01

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