---
title: "Which drill bit should I use for plastic?"
description: "An HSS bit ground to a shallower rake, or a plastic-specific bit, at low speed with a backing board — acrylic especially will crack. The ranked options, the techniqu"
url: https://atoneplace.net/which/drill-bit-plastic/
site: "At One Place"
---

# Which drill bit should I use for plastic?

**Which drill bit should I use for 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.**

Plastics fail in two opposite ways under a drill. Brittle sheet like acrylic cracks because a standard twist drill has a positive rake that pulls itself into the material and, at breakthrough, snatches through the last thin web. Soft plastics melt because they conduct heat poorly and the swarf re-welds behind the bit, seizing it in the hole. The answers are correspondingly opposite: reduce the rake and support the exit for brittle plastics, and increase speed of chip clearance while reducing heat for soft ones. Backing the workpiece with scrap is the single most effective step for both, and peck drilling — withdrawing repeatedly — keeps the flutes clear and the temperature down.

## The options, ranked

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

| Option | Good at | Bad at |
| --- | --- | --- |
| Plastic-specific drill bit | Ground with almost zero rake so it scrapes rather than grabs, which is exactly what brittle acrylic needs. | A separate purchase, and slower in every other material. |
| Standard HSS bit | Fine in soft plastics such as polyethylene, polypropylene and PVC. | Its aggressive rake screws itself into acrylic and polycarbonate and cracks the sheet at breakthrough. |
| Step bit | Excellent in thin sheet — it enlarges gradually and cannot grab. | Thin material only, and it leaves a chamfered hole. |
| Spade or Forstner bit | Useful for large holes in thick sheet at very low speed. | Melts the plastic if run fast, welding the swarf back into the hole. |

## Technique that changes the outcome

1. Clamp a scrap backing board tight against the exit face
2. Run at low speed with light, steady pressure
3. Peck-drill: withdraw every few seconds to clear swarf and heat
4. For acrylic, blunt a spare bit slightly by honing the cutting edge to near-zero rake
5. Leave the protective film on the sheet while drilling

## What goes wrong

- A sharp new twist drill straight into thin acrylic
- High speed in soft plastics, which melts and welds the swarf
- Drilling close to an edge without support, where acrylic splits along the hole

> 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. |
| 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 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.

### What should I avoid?

A sharp new twist drill straight into thin acrylic High speed in soft plastics, which melts and welds the swarf Drilling close to an edge without support, where acrylic splits along the hole

## 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 will go through hardened steel?](https://atoneplace.net/which/drill-bit-hardened-steel/)
- [Which glue works on plastic?](https://atoneplace.net/which/glue-plastic/)
- [Which sandpaper grit for plastic?](https://atoneplace.net/which/sandpaper-plastic/)
- [Which paint sticks to plastic?](https://atoneplace.net/which/paint-plastic/)
- [Which screw should I use in plastic?](https://atoneplace.net/which/screw-plastic/)

## Sources

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