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Download O6 Spec sheet

WM O-6 is an oil-hardening, graphitic tool steel with outstanding resistance to metal-to-metal sliding wear and galling. The steel contains a uniform dispersion of graphite particles, which impart excellent machinability and non-seizing characteristics. The graphite particles make the steel self-lubricating in dry environment, and help to retain oil in lubricated environments.

WM O-6 can be hardened to over 60 Rockwell C from a relatively low hardening temperature, which minimizes size change and distortion during heat treatment.


Carbon 1.45
Manganese 1.00
Silicon 0.90
Molybdenum 0.25


Thread gauges, master gages, cams, bushings, sleeves, meat granulator plates, arbors, forming rolls, shear blades, punches, dies, bar feed guides, and other machine tool parts.


Density – 0.278 lb/in3

Specific gravity – 7.70

Coefficient of Thermal Expansion

70 – 400°F 6.23 x 10-6 in/in/°F
70 – 600°F 6.74
70 – 800°F 7.06
70 – 1000°F 7.23
70 – 1200°F 7.56


Heat at a rate not exceeding 400°F per hour to 1200-1250°F and equalize.


Heat slowly from the preheat to 1450-1550°F
– Less than ½ inch thickness: use 1450°F
– ½ to 2 inches thickness: use 1475°F
– Over 2 inches thickness: use 1500°F


Oil or pressurized gas.
For oil, quench to 150-125°F
For pressurized gas, the quench rate to below 1000°F should be a minimum of 400°F per minute, and is critical for obtaining the desired properties.


Temper immediately after quenching.

The typical tempering range is 300-400°F. Hold at temperature for 1 hour per inch of thickness, 2 hours minimum, then air cool to ambient temperature. The actual hardness obtained is dependent upon the section size of the part being quenched and tempered.

To minimize internal stresses in cross sections greater than 3 inches and to improve stability in parts that will be EDM’d after heat treatment, a soaking time of 4-6 hours at the tempering temperature is strongly recommended.

Cryogenic Treatment: Refrigeration treatments should typically be performed after the temper, and must be followed by a second temper.



Annealing must be performed after hot working and before rehardening.

Heat at a rate not exceeding 400°F per hour to 1450°F, and hold at temperature for 1 hour per inch of maximum thickness, 2 hours minimum. Then cool at 10°F per hour to 1300°F. Then cool at 25°F per hour from 1300°F to 1000°F. Then cool in air to ambient temperature. The resultant hardness should be a maximum of 229 HBW.

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