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 Oil Hardening Tool Steel 

Precision Marshall’s PRESCO is a general purpose, non-deforming oil hardening tool steel for applications where maximum accuracy is required during the hardening of the end product. PRESCO has deep hardening properties and fine grain structure with unusual toughness. Meets ASTM A-681 and W 2510. 

Phosphorus.03 maxSilicon.40
Sulfur.03 max


Applications for PRESCO include gauges, stamps, jigs, cutters, templates, cams, guides, levers, saws, knives, straight edges, fixtures, machine parts, punches, blanking dies, molding dies, swaging dies, screw dies and trim dies. 


Heat uniformly to 1400/1450°F and hold at the annealing temperature for two hours per inch of cross section. Cool in the furnace at a rate not exceeding 50°F per hour down to a temperature of 1000°F, after which a faster rate can be allowed. 

Heat Treating

Preheat thoroughly to 1200/1250°F, then heat to 1450/1500°F depending on the section size. Hold until uniformly heated through. Use high side of hardening range for thicker sections. 

Quench in warm thin quenching oil to about 125°F. To prevent soft spots, the tools should be rapidly agitated in oil when a circulating oil bath is not available. The material should be tempered as soon as it has cooled to 125°F. 


Temper immediately to desired hardness. For most applications a tempering temperature of 400/450°F is employed. However, for cutting tools requiring high hardness, low temperatures of 300/375°F are suitable. Temper a minimum of two hours for sections under two inches and a minimum of one hour per inch of thickness over two inches. 

The following table shows the hardness value obtained at various tempering temperatures on a two-inch cube of PRESCO hardened from 1475°F and tempered two hours. 

 Tempering Temperature (°F) Rockwell Hardness (RC) 
As quenched 63/65 
300 62/64 
400 60/62 
500 57/59 
600 55/57 


Electro-discharge machining is used in the production of various tooling. This process produces recast, rehardened and retempered layers on the EDM surface. It is recommended that PRESCO O-1 be stress relieved at 50°F below the final tool tempering temperature, after the EDM process, to temper the rehardened layer produced by EDM. 


PRESCO O-1 is provided completely decarb free and stress relieved. 


Ground oversize to typical rms 50/75, maximum 125. 


Available in standard thickness increments 1/4” thru 2”.