Metal has been one of the most important advances in human history. Wood, stone, and just about everything in between is easy to work with metal tools. But what do you use when you need to work metal? Tool steel.
Tool steel is a versatile class of metals. As the name implies, they are well-suited to making tools. Their main benefits are that they are particularly hard metals that withstand heat and resists abrasion. Tool Steel is available in a number of grades that are each suited to specific applications, such as punches, dies or cutting applications. What do these numbers mean though? How do you decide what grade to use for your purposes? We’re here to help answer that!
Tool Steel Grades
These metals all typically come in an annealed state. This softness allows you to work them into the shape you want. After that, you can harden them to the hardness you need. However, the method used to harden the piece depends on the grade of tool steel selected. Essentially there are three methods of hardening tool steel. Air, oil, and water.
Air hardened tool steels are also called self-hardening steel. These are heated up above their transformative temperature then allowed to cool in the air. This allows for a slow, even cooling that minimizes distortion. Also, air cooled steels tend to have intermediate hardness.
Water-cooled tool steel is the most popular type because it is the cheapest. Their popularity is declining in favor of oil-cooled, but for the time water is still the most common. Water-cooled steels are softer and more prone to cracking and distortion than other types of quenching.
The last method of quenching is oil-cooling. This method falls between air and water cooling. Specifically, it cools quickly like water. But it avoids the risk of cracking and distorting like water. Oil-cooled tools tend to have stronger surfaces but softer cores. This makes them useful for tools like blades or shears.
The most commonly available of the tool steels, 1018 has a good combination of all of the typical traits of steel. Strength, some ductility, and comparative ease of machining make this metal widely useful. 1018 is one of the air-hardened varieties of tool steel.
Typically, 1018 is used in pins, rods, shafts, spindles, and sprockets.
A versatile, all-purpose tool steel. A-2 is air-hardened with good strength and low distortion during heat treatment. Also, it machines well and is tough. Lastly, A-2 steel exhibits wear resistance that falls between O-1 and D-2 steel.
Typically, A-2 is used in punches, dies, cutting tools in woodworking, tooling for plastic, dowel pins, hammers, and industrial knives.
A high-carbon, air-hardening tool steel with excellent machinability. Also, D-2 has excellent resistance to wear, chipping, cracking and minimal distortion during cooling. These factors make it a great choice for tools specifically designed for long service lives. Overall, D-2 provides a good blend of toughness, strength, and affordability.
Typically, D-2 is used in rolls, punches, files, shear knives, food processing knives, woodworking knives, knurling tools, and gauges.
Designed for high toughness and very good stability during heat treatment. H-13 also has excellent shock and abrasion resistance. Furthermore, it has added strength and hardness to allow it to operate at high temperatures for prolonged periods.
Typically used in cores, hot shear knives, hot trimming tools, hot extrusions, cavities for dies, and tools that require toughness.
The most popular tool steel for high-speed applications. M-2 has excellent toughness, wear resistance, and has an affordable price point.
Typically, M-2 is used in drills, taps, milling cutters, reamers, saws, punches, and knives.
An oil-hardening, general purpose tool steel. O-1 holds its size and shape with excellent accuracy when being heat treated. Additionally, O-1 machines easily, with good abrasion resistance and toughness. Though not as strong or wear resistant as A-2 or D-2, it experiences significantly less distortion during the heat treating process.
Typically, O-1 used in rolls, punches, shear knives, food processing knives, knurling tools, drill bushes, and gages.
An oil or air-hardened tool steel that exhibits excellent high impact toughness and strength. Also, S-7 machines easily. However, as a trade off, S-7 has lower than average abrasion resistance.
Typically, S-7 is used in shear blades, battering tools, blacksmith tools, dies, chisels, chipper knives, and punches.
A water hardening tool steel. W-1 is one of the most commonly used tool steels due to high strength, ease of machining, and low cost. However, it does undergo a decent amount of distortion and possibly cracking during quenching. Also, it is more brittle than other steels.
Typically, W-1 is used in shafts, pins, blacksmithing tools, knives, reamers, cutlery, and short term wearing tooling.