Eastern Tool
Steel Service, Inc.

1045 Delaum Rd.

P.O. Box 857

St. Marys, Pa 15857

Phone: (814) 834-7224
Fax: (814) 834-7225
Contact Us




O-1 Tool Steel Data Sheet

AISI O-1 is an oil-hardening tool steel which may be hardened from fairly low temperatures with little size change. O-1 combines deep-hardening qualities with a fine-grained structure, affording good initial production runs, and good continued production after grinding.

Chemical Composition

Carbon 0.90%
Manganese 1.25%
Chromium 0.50%
Silicon 0.50%
Tungsten 0.50%

Typical Applications

Blanking Dies Engraving Tools
Forming Dies Gauges
Knives Shear Blades

Cold Work Tool Steel Comparison Chart

Thermal Treatments

Note: Full hardness will only be attained in sections less than 3" thick

Preheat : 1250/1350F (675/730C), equalize

Austenize : 1450/1500F (790/815C), 30/45 minutes at temperature.

Quench : Oil to 150F (65C).

Temper : 350/600F (175/315C), hold 2 hours at temperature, air cool. Temper twice.

Cryogenic Treating : Refrigeration treatments may improve long term dimensional stability by transforming retained austenite. Refrigeration treatments should generally be performed after the first temper, and must be followed by a temper.

Hardness and Impact Toughness Data
Oil Quenched from 1475F(800C)

Tempering Toughness
Temperature HardnessCharpy C-Notch
Deg. FDeg. CHRCFt. Lbs.Joules
As quenched 65 -
300 150 64 14 19
3501756328 38
400 205 62 30 41
450 230 61 30 41
500 260 59 30 41
600 315 56 32 43
700 370 52 - -
800 425 49 - -
900 480 44 - -
1000 540 40 - -

Surface Treatments

O-1 can be given standard surface treatments such as hard chrome plating if desired. Nitriding is not generally practical due to a substantial loss of core hardness.


A. Heat to 1425/1450F(775/790C), hold two hours, cool slowly, 50F(30C) per hour maximum, to below 1000F(540C), then air cool.
B. Heat to 1425/1450F(775/790C), hold 2 hours, cool to 1275F(690C) 6 hours, then air cool.
Typical annealed hardness: 187/221 BHN.

Stress Relieving

Annealed Material: Heat to 1100/1300F(595/705C), hold two hours, cool in still air.
Hardened Material: Heat to 50F(15C) below original tempering temperature, hold two hours, cool in still air.


Use oil hardening (O-1) tool steel filler material.

Annealed Material:Preheat to 400/600F(205/315C). Maintain above 400F(205C) during welding. Reanneal or temper 1250/1300F(675/700C) 6 hours.

Hardened Material: Preheat to 50F(15C) below original tempering temperature (300F(150C) minimum). Maintain above 300F(150C) during welding. Cool to 150F(65C) after welding. Retemper twice 25F(15C) below original tempering temperature.

Physical Properties

Modulus of Elasticity
30psix10(6)(207 GPa)
Density0.283 lb/in3(7850 kg/M3)
Thermal Conductivity20 BTU/hr./ft./F34 W/m/ K)

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