Tool Steel: A Comprehensive Guide
Tool steel is used in the making of so many products that we all use on a daily basis – we’d be a bit lost without it! The versatility of tool steel makes it applicable in the shaping of a whole range of materials.
With so many different types of tool steel, however, it can be a little confusing. With that in mind, we’ve used our expert in-house knowledge to create this comprehensive guide to tool steels.
What is Tool Steel?
Tool steel encompasses a wide variety of carbon and alloy steels that have particular mechanical or physical properties, such as strength, hardness, workability, abrasion, corrosion and heat resistance.
This makes them well suited to be made into tools, essentially used in the shaping of other materials, and especially for drilling and cutting as they are able to hold a cutting edge at elevated temperatures.
Tool steels contain differing amounts and combinations of tungsten, molybdenum, cobalt and vanadium.
What’s the difference between tool steel and high speed steel?
High-speed steel (HSS or HS) is a sub-group of tool steel with high carbon & high alloy content that is hardenable and can withstand the sort of high temperatures (400-600 degrees celsius) you get when turning, milling and drilling.
As a result they are commonly used in tool bits and cutting tools, such as power-saw blades and drill bits, where they can cut faster than high carbon steels which would lose their hardness (temper) if used in such temperatures.
What is Tool Steel used for?
Tool steel is used to make other products, for cutting, stamping, punching and machining other metals, plastics and wood. They are usually supplied in a soft annealed condition, machined into the tools required, then heat-treated to improve their hardness.
Tool Steel Grades
There are several types of tool steel grades:
Tool Steel Properties
The tool steel that is most appropriate for an application will depend on the combination of properties required.
The primary tool steel properties are:
High speed tool steel properties
- High strength at high temperatures
- Good toughness
- High compressive strength
- Good wear resistance
Comparing Tool Steel Grades
01 vs 02 tool steel
The two steels are very close in properties, both cold-work steels used for cutting tools like knives and blades. O2 has a slightly higher level of manganese (Mn) giving slightly better hardening properties. O1 tool steel is a bit more corrosion resistant and can keep a slightly better edge.
01 tool steel vs D2
O1 & D2 tool steel are both cold work steels, used for cutting tools. D2 can be sharpened to a greater degree. O1 is the strongest and the easiest to sharpen, but less rust resistant. D2 with its high chromium content is semi-stainless.
M2 tool steel vs D2
M2 is a popular high speed steel, whereas D2 is a cold work steel. M2 & D2 are about the same toughness, but M2 tool steel will hold a better edge as the grain structure is finer, but it is not very corrosion resistant & can rust, whereas D2 is semi-stainless.
A2 tool steel v D2
Both are cold work steels, with very high hardness after heat treatment. A2 tool steel is a multipurpose tool steel, offering a combination of good wear resistance and high toughness. D2 tool steel is harder and more wear-resistant, but less tough and a little more brittle.
Tool Steel FAQs
How do you drill tool steel?
You can drill into hardened tool steel with either a carbide bit or a diamond bit but it will most likely need cooling. A commercial metal working shop would do this with either a plasma cutter or a water jet cutter.
How do you soften tool steel?
To soften tool steel, and make it easier to work with, heat it up to 100 degrees F above its critical temperature in a heat treat oven or forge (this will be different for each grade of steel), soak it at that temperature for one hour for every inch of thickness and let it cool in a slow controlled way at a maximum rate of 70 F per hour.
How do you machine tool steel?
Tool steel is usually supplied in the soft annealed condition, so it can be machined into the required tool shape, then hardened.
What is the hardest tool steel?
Hardness in tool steel is measured by the Rockwell C test, whereby a standardised load is used to make an indentation. A small indentation indicates high hardness. Hardened cold work tool steels are generally about 58/64 HRC (hardness Rockwell C). Most are circa 60/62 HRC, although some can go up to 66 HRC.
The hardest tool steels are the ones with the highest content of vanadium carbides, for example A7 & D7 are high vanadium versions of A2 & D2
Looking for a tool steel supplier?
AKM Steels is one of the UK’s leading tool steel suppliers and stockholders. Contact us today for quote.