Key Steel

Here at Cromwell we stock an extensive choice of engineering materials including key steel. Available in a wide range of lengths and thicknesses, we supply durable, quality key steel from market-leading brands like Bonut Engineering Ltd® and our own brand Kennedy®.

What is key steel?

Manufactured from pure carbon steel, key steel is manufactured in square and rectangular bars and can feature plating, a shiny finish or be a self-coloured final product.

Why key steel?

Used for creating tools, small components and machine keys for gears and pulley mechanisms, key steel is supplied in a wide range of lengths to reduce waste material.

Key steel types

Available as individual lengths in metric and in a variety of finishes, key steel is often used in the construction of taper, Gibhead, plain and parallel keys.

• Square   -   available in a range of widths and heights for precision machining

• Rectangle   -   available in metric sizing, all rectangle bars vary in width and length

Considerations when choosing key steel

Dimensions - usually key steel is supplied in set stock lengths, but to avoid wastage, choose the width and length most suited to your requirements.

Finish - key steel can be self-coloured, shiny stainless steel or plated with non-corrosive metals, such as zinc.

Tolerance - this measurement should be available on technical data sheets and relies on the application the key steel will be used for.

Key steel jargon buster

Quality standards can be a minefield to navigate, so, to help you with your purchase we've put together a brief outline of quality standards relating to key steel.

What does the standard BS 4235-1:1972 mean?

This standard covers parallel and taper key steel manufactured between 6mm to 500mm in diameter and classified under ICS category 21.120.30. It outlines the dimensions and tolerances required in square parallel, rectangular parallel, square taper, gib-head and plain, and rectangular taper, gib-head and plain.

Let's break it down...

• BS - This standard was published by the British Standards Institute

• 4235 - The assigned legislation number

• 1 - The part of the document that relates to parallel and taper key steel

• 1972 - The year this standard was published. It's since been checked and confirmed in 2007


Is key steel EN8?

Key steel is similar in structure to EN8 and is a good alternative in that it's a pure carbon, medium steel that's durable and has excellent machining properties for a range of structural and machine applications.

Can key steel be hardened?

Key steel is quite tough with good tensile strength, so it's unusual practice to harden it. However, it can be done using conventional heat methods like induction or flame treatment.