---
title: "Which drill bit will go through hardened steel?"
description: "Solid carbide in a rigid setup, or soften the spot first — HSS and cobalt cannot cut anything much above 50 HRC. The ranked options, the technique that changes the o"
url: https://atoneplace.net/which/drill-bit-hardened-steel/
site: "At One Place"
---

# Which drill bit will go through hardened steel?

**Which drill bit will go through hardened steel?: Solid carbide in a rigid setup, or soften the spot first — HSS and cobalt cannot cut anything much above 50 HRC.**

A cutting tool has to be substantially harder than the material it cuts. HSS sits around 62-65 HRC and cobalt HSS a little above, but they both lose hardness as they heat, so against a component hardened to 55-60 HRC they blunt almost instantly. Tungsten carbide stays hard to far higher temperatures and can cut it — at the cost of being brittle, so any wobble, any hand-held wander, and the tip chips. Rigidity therefore matters as much as the bit: clamp the work, use a press or a stable guide, run slowly, and use steady pressure without hammering. If the part's heat treatment does not matter, annealing the spot is far easier than fighting it.

## The options, ranked

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

| Option | Good at | Bad at |
| --- | --- | --- |
| Solid carbide bit | Hard enough to cut a hardened bolt, a file or a lock shackle where nothing else will. | Brittle to the point of snapping under any side load, so it needs a drill press and a clamped workpiece. |
| Carbide-tipped masonry bit, reground | A well-known field improvisation: the carbide tip cuts, once ground to a sharper cutting angle. | Crude, slow, leaves a rough hole and needs a bench grinder and patience. |
| Annealing the spot | Heating the area red and letting it cool slowly softens it so ordinary bits work again. | Destroys the heat treatment of the part, which may be exactly what the part relies on. |
| Abrasive or spark erosion | A carbide burr, a die grinder or professional EDM will remove hardened material without a drill. | Slow, or requires equipment most people do not have. |

## Technique that changes the outcome

1. Clamp the work and use a drill press or a solid guide; hand drilling snaps carbide
2. Run slow — a few hundred rpm — with firm continuous pressure
3. Cool with cutting fluid to protect the bit rather than the workpiece
4. Start with a carbide spotting or centre drill so there is no chance of wandering

## What goes wrong

- Hammer mode, which shatters carbide instantly
- Cobalt bits marketed as suitable — they are for stainless, not for hardened steel
- Annealing a spring, a fastener or a structural part whose hardness is doing a job

> 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. |
| Glass | A spear-point carbide or a diamond bit, run slowly under water — and toughened glass cannot be drilled at all. |
| 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. |
| 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 will go through hardened steel?

Solid carbide in a rigid setup, or soften the spot first — HSS and cobalt cannot cut anything much above 50 HRC.

### What should I avoid?

Hammer mode, which shatters carbide instantly Cobalt bits marketed as suitable — they are for stainless, not for hardened steel Annealing a spring, a fastener or a structural part whose hardness is doing a job

## 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 glass?](https://atoneplace.net/which/drill-bit-glass/)
- [Which drill bit should I use for plastic?](https://atoneplace.net/which/drill-bit-plastic/)

## Sources

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