---
title: "Tool steel — density, melting point and properties"
description: "Tool steel has a density of 7,800 kg/m³ (7,700–7,900). Melting point, strength, conductivity, what it is used for, and whether it floats, rusts or is magnetic."
url: https://atoneplace.net/material/tool-steel/
site: "At One Place"
---

# Tool steel

**Density of tool steel: 7,800 kg/m³ (7,700–7,900)**

7.80 g/cm³ · 486.9 lb/ft³

A family, not a material: O1 hardens in oil and is forgiving, A2 hardens in air and moves less, D2 has 12% chromium and holds an edge far longer but will not take as fine a one, and M2 high-speed steel stays hard at red heat. The 600-2000 MPa span is annealed stock through fully hardened and tempered — a tool steel is soft when you machine it and only becomes a tool afterwards. Thermal conductivity is left blank here on purpose: it runs from about 20 W/(m·K) for D2 to 46 for O1, and a single figure would mislead.

## Properties

- **Density:** 7,800 kg/m³ (7,700–7,900) — 7.80 g/cm³
- **Melting range:** 1420–1500 °C
- **Tensile strength:** 600–2000 MPa
- **Young's modulus:** 200 GPa
- **Thermal expansion:** 11 µm/(m·K)
- **Floats in water:** No
- **Magnetic:** Yes

## What it is used for

- Punches, dies and press tooling
- Milling cutters, drills and taps
- Injection mould cavities
- Woodworking chisels and plane irons

## How it compares

*Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.*

- air: 1.2 kg/m³
- expanded polystyrene foam: 20 kg/m³
- rigid polyurethane foam: 40 kg/m³
- Water — the float line: 1,000 kg/m³
- tool steel: 7,800 kg/m³
- tungsten: 19,250 kg/m³
- gold: 19,300 kg/m³
- platinum: 21,450 kg/m³

*Water is 1,000 kg/m³. Anything below that floats.*

| Material | Density | Relative to water |
| --- | --- | --- |
| rigid polyurethane foam | 40 kg/m³ | 0.04× |
| expanded polystyrene foam | 20 kg/m³ | 0.02× |
| air | 1.2 kg/m³ | 0.00× |
| tool steel ← | 7,800 kg/m³ | 7.80× |
| platinum | 21,450 kg/m³ | 21.45× |
| gold | 19,300 kg/m³ | 19.30× |
| tungsten | 19,250 kg/m³ | 19.25× |

## Does it rust?

Yes, and readily. Rust is iron oxide, and it is flaky rather than adherent — it does not seal the surface, so oxygen and water keep reaching fresh metal underneath and the process continues until the section is gone. That non-protective quality is what makes rust different from the oxide layers on other metals.

## Is it magnetic?

Iron, nickel and cobalt are the three common ferromagnetic elements, and anything based mostly on them is strongly attracted to a magnet.

## Common questions

### What is the density of tool steel?

7,800 kg/m³ (7,700–7,900), or 7.80 g/cm³.

### Does tool steel float?

No. At 7,800 kg/m³ it is denser than water.

### Is tool steel magnetic?

Iron, nickel and cobalt are the three common ferromagnetic elements, and anything based mostly on them is strongly attracted to a magnet.

## Related pages

- [Does tool steel float?](https://atoneplace.net/does-it-float/tool-steel/)
- [Mild steel](https://atoneplace.net/material/mild-steel/)
- [Stainless steel 304](https://atoneplace.net/material/stainless-304/)
- [Brass](https://atoneplace.net/material/brass/)
- [Gray cast iron](https://atoneplace.net/material/cast-iron/)
- [High-carbon steel](https://atoneplace.net/material/carbon-steel/)
- [Stainless steel 316](https://atoneplace.net/material/stainless-316/)
- [Aluminum 6061](https://atoneplace.net/material/aluminum-6061/)
- [Bronze](https://atoneplace.net/material/bronze/)

## Sources

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