---
title: "Which drill bit should I use for glass?"
description: "A spear-point carbide or a diamond bit, run slowly under water — and toughened glass cannot be drilled at all. The ranked options, the technique that changes the out"
url: https://atoneplace.net/which/drill-bit-glass/
site: "At One Place"
---

# Which drill bit should I use for glass?

**Which drill bit should I use for glass?: A spear-point carbide or a diamond bit, run slowly under water — and toughened glass cannot be drilled at all.**

Glass has no ductility, so every hole is made by abrading it away and every stress concentration becomes a crack. Heat is the main enemy: a dry bit produces a local hot spot, and glass conducts heat so poorly that the thermal gradient alone will split it, which is why water is compulsory rather than helpful. The other critical rule is that toughened, tempered and heat-strengthened glass cannot be drilled or cut at all — the surface is under compression balancing a tensile core, and breaching it releases the whole panel into a shower of granules instantly. Toughened glass has to be cut and drilled before tempering, so a shower screen or an oven door simply cannot be modified.

## The options, ranked

*Ranked best-first for the stated job. The third column is why the others exist.*

| Option | Good at | Bad at |
| --- | --- | --- |
| Spear-point carbide glass bit | Cheap and effective for small holes in ordinary annealed glass and mirrors. | Chips the exit face unless the glass is backed, and blunts fast. |
| Diamond hole saw | Cleanest cut, and the right tool above about 8 mm or in thick glass. | Needs water and patience; it grinds rather than cuts. |
| Ordinary masonry bit | Occasionally works on very soft glass in an emergency. | Wrong grind, high chipping risk, and likely to crack the piece. |

## Technique that changes the outcome

1. Support the glass flat on a soft backing such as MDF or a folded towel
2. Build a plasticine dam and fill it with water, or drip continuously
3. Very low speed and gentle pressure; let the abrasive do it
4. Slow down further at breakthrough and, on thick glass, drill halfway from each side

## What goes wrong

- Any attempt on toughened or laminated glass — the first shatters and the second delaminates
- Drilling dry, which cracks the pane from thermal stress
- Drilling within about 20 mm of an edge, where the stress concentration is highest

> Compiled practical guidance rather than a published standard. Product formulations vary by brand and market, so read the label — and where the work is structural, electrical or gas, the regulations that apply where you are govern rather than anything here.

## Other drill bit questions

| For | Use |
| --- | --- |
| Tile | A spear-point carbide or diamond bit in rotary mode only — hammer action shatters tile, every time. |
| Metal | An HSS twist drill, ideally with a 135° split point, run slowly with firm pressure and cutting fluid. |
| Concrete | An SDS-plus carbide bit in a rotary hammer — a normal hammer drill will get there eventually and blunt several bits doing it. |
| Masonry | A carbide-tipped masonry bit in hammer mode for brick and block; step up to an SDS rotary hammer above about 10 mm. |
| Porcelain tile | A diamond core bit, cooled with water, at low speed — carbide spear points do not cut porcelain. |
| Stainless steel | A cobalt bit at low speed with heavy constant pressure and cutting fluid — and never let it stop cutting. |
| Wood | A brad point bit for clean holes up to about 13 mm; an auger for depth and a Forstner for a flat bottom. |
| Plasterboard (drywall) | Almost none — an ordinary HSS or brad point bit in rotary mode, and the real question is which fixing goes in the hole. |
| Plastic | An HSS bit ground to a shallower rake, or a plastic-specific bit, at low speed with a backing board — acrylic especially will crack. |
| Hardened steel | Solid carbide in a rigid setup, or soften the spot first — HSS and cobalt cannot cut anything much above 50 HRC. |
| Aluminium | A sharp HSS bit at high speed with a wax or paraffin lubricant — the problem is aluminium sticking to the bit, not hardness. |
| Large holes in wood | Spade for speed and roughness, auger for depth, Forstner for a clean flat bottom, hole saw for big diameters in thin stock. |

## Common questions

### Which drill bit should I use for glass?

A spear-point carbide or a diamond bit, run slowly under water — and toughened glass cannot be drilled at all.

### What should I avoid?

Any attempt on toughened or laminated glass — the first shatters and the second delaminates Drilling dry, which cracks the pane from thermal stress Drilling within about 20 mm of an edge, where the stress concentration is highest

## Related pages

- [Which drill bit should I use for tile?](https://atoneplace.net/which/drill-bit-tile/)
- [Which drill bit should I use for metal?](https://atoneplace.net/which/drill-bit-metal/)
- [Which drill bit should I use for concrete?](https://atoneplace.net/which/drill-bit-concrete/)
- [Which drill bit should I use for masonry?](https://atoneplace.net/which/drill-bit-masonry/)
- [Which drill bit should I use for porcelain tile?](https://atoneplace.net/which/drill-bit-porcelain-tile/)
- [Which drill bit should I use for stainless steel?](https://atoneplace.net/which/drill-bit-stainless-steel/)
- [Which drill bit should I use for wood?](https://atoneplace.net/which/drill-bit-wood/)
- [Which drill bit should I use for plasterboard?](https://atoneplace.net/which/drill-bit-plasterboard/)
- [Which drill bit should I use for plastic?](https://atoneplace.net/which/drill-bit-plastic/)
- [Which drill bit will go through hardened steel?](https://atoneplace.net/which/drill-bit-hardened-steel/)
- [Which glue works on glass?](https://atoneplace.net/which/glue-glass/)
- [Which blade cuts glass?](https://atoneplace.net/which/blade-glass/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)