O1 Tool Steel

General purpose oil-hardening. Good machinability, low distortion. Used for dies, punches, gauges.

Reference ratings

• Type: Cold Work
• Hardness: 57-62 HRC
• Wear resistance: 4/10
• Toughness: 5/10
• Machinability: 8/10

Selection considerations

O1 is not a first choice where abrasive wear dominates, has moderate shock tolerance, machines easily in the annealed condition. At 57-62 HRC it sits in the cold work family, so the quench medium, section size, and distortion allowance should be planned together — a grade that rates well on wear but low on toughness will fail by chipping long before it wears out if the application is wrong.

Use the ratings here for comparison, then confirm the grade-specific data sheet and heat-treatment instructions from the selected supplier. Specify hardness range, heat-treatment process, finish stock, coating sequence, and inspection requirements on the tooling record. Large sections, sharp corners, interrupted cuts, and repair welding can materially change risk.

Sourcing and data sheets

• Cincinnati Tool Steel
• Alro Steel

Production verification

Review the application with the tool designer, heat treater, and responsible engineer before release. Track wear and failure mode after startup so the next maintenance or replacement decision uses actual performance instead of a generic ranking. These values are reference data and are not a heat-treatment certificate.

Open the tool steel comparison matrix, read choosing tool steel for stamping dies, or return to tooling materials.