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The OnlineMetals Guide to Tool Steel


The term Tool Steel is a generic description of steel which has been developed specifically for tooling applications. Generally speaking, Tool Steels are known for their distinctive toughness, resistance to abrasion, their ability to hold a cutting edge, and/or their resistance to deformation at elevated temperatures (red-hardness). Some of the operations that tool steels are used in include Drawing, Blanking, Mold Inserts, Stamping, Metal Slitting, Forming and Embossing, although they are not limited to just those areas.


Tool Steels are produced in the annealed condition for ease of machining. After machining, the steel is heat-treated and quenched depending upon the type of steel being used. The heat treating and quenching operations increase the toughness and strength of the material.


There are three classes of tool steel generally available in the market today - cold work, hot work, and high speed steel:
  • Cold Work steels have high strength, hardenability, impact toughness, and wear resistance. As the name would imply, they are used in environments with lower operating temperatures, typically at 400° or less. The materials that we carry that fall into the Cold Work category are O1, A2, D2, S7 and W1.
  • Hot work steels have many of the same properties of cold working steels, with the added advantage that that those properties are retained at elevated operating temperatures where the tool literally becomes red-hot.
  • High speed steels have all of the properties listed above, but retain those properties in operating areas where the temperatures exceed 1000° F.

Tolerances of Tool Steel 

Drill Rod Tolerances
Diameter Diameter Tolerance Straightness Length Tolerance
.124” and less +/- .0003” .005” +1/8”, -.0”
.499“ to .125” +/- .0005” .005” +1/8”, -.0”
3.000” to .500” +/- .0010” .005” +1/8”, -.0”


Ground Flat Stock Tolerance
Thickness Width Length 18” Length 36" Squareness Edge Squareness End
+/-.001” +.000/.005 +.125/.250” +.250/.500” .003”/in. .004” /in.



Oversize Flat Stock Tolerance
Thickness Width Length 18” Length 36" Squareness Edge Squareness End
+.010/.015” +.000/.005 +.125/.250” +.250/.500” .003”/in. .004” /in.


Square Bar Tolerances
Ground Stock Oversized Length 18” Length 36" Squareness Edge Squareness End
+/-.001” +.010/.015” +.125/.250” +.250/.500” .003” per inch .004” per inch


The basic properties of the tool steel carried by are listed below:


W-1 Tool Steel
  Heat treat temperature 1450-1600 F
  Quench Water or Brine
  Hardness Rockwell 56c
  Applications Blacksmith tools
Cold Chisels
Hand punches
Cold Forming Tools
Scissors and Shears
Woodworking Chisels
  Disadvantages Water hardening tool steels tend to experience significant distortion during the quench operation. In addition, the hardening operation applies only to the outer "case" of the material, rather than being "through-hardened".


O-1 Tool Steel
  Heat treat temperature 1450-1600 F
  Quench Oil
  Hardness Rockwell 62c-64c
  Applications Taps
Knurling Tools
Shear Blades
Coining Dies
Trimming Dies
  Disadvantages Oil hardening tool steels tend to experience less distortion during the quench operation, but they do still show distortion from the original size. The hardening operation is more thorough than with water hardening steels, but not as thorough as the air-hardening grades.


A-2 Tool Steel
  Heat treat temperature 1700-1900 F
  Quench Air
  Hardness Rockwell 59c-62c
  Applications A2 can be used in the same applications as both O1 and W1, but the heat-treated air-hardening steels have deeper hardenability and there is less movement or distortion during heat treatment.


S-7 Tool Steel
  Heat treat temperature 1725-1750 F
  Quench Air or Oil
  Hardness Rockwell 55c-57c
  Applications S7 is good for general tooling and molding applications. It possesses high toughness and shock resistance.
  Disadvantages While S7 is very tough compared to other tool steels, it doesn't have hardness comparable to the other tool steels.


D-2 Tool Steel
  Heat treat temperature 1600-1650 F
  Quench Air or Oil
  Hardness Rockwell 60c-62c
  Applications D2 has high wear resistance, good toughness, and low distortion. It is often chosen when long tool life is required.