Starrett 56990 O1 Tool Steel Flat Stock 5/16x1x18 in

Product Description

The STARRETT 56990 is an O1 oil-hardening tool steel flat stock bar used in toolmaking, die work, punches, and precision machining applications. It measures 5/16 inches thick, 1 inch wide, and 18 inches long, and is manufactured to AISI Type O1 material specification. Thickness and width tolerances run from +0.010 to +0.015 inches, length tolerance is +0.250 inches, and squareness is held to 0.003 inches per inch on all edges. The stock ships in an annealed, machinable condition ready for machining, grinding, and subsequent oil-hardening heat treatment. Machinists, tool-and-die makers, and toolroom technicians are the primary users of this material.

O1 tool steel flat stock is suited for low-to-medium production tooling where oil-quench hardening is the chosen heat treatment method. Typical applications include blanking punches, forming dies, drill jigs, gauges, and small machine parts requiring a hardened working surface. This bar stock is commonly used in job shops and toolrooms handling one-off and short-run tool fabrication where tight dimensional tolerances on raw stock reduce pre-machining setup time.

Key Features

• AISI Type O1 oil-hardening tool steel for predictable, controlled heat treatment response
• Tight dimensional tolerances: +0.010 to +0.015 inches on thickness and width
• Squareness held to 0.003 inches per inch on all edges for accurate layout and setup
• 18-inch length with +0.250-inch length tolerance provides usable stock with minimal waste
• Annealed condition allows machining, drilling, and grinding before hardening
• Single-piece minimum order quantity suits low-volume toolroom and prototype work

Compatibility

Designed as a standard AISI O1 oil-hardening tool steel flat bar compatible with conventional toolroom heat treatment processes requiring oil-quench hardening.

Installation Notes

Machining and grinding operations should be completed before heat treatment. Oil-hardening heat treatment of O1 tool steel should be performed by a qualified heat treater or toolroom professional following established metallurgical procedures. Use appropriate personal protective equipment when handling during and after heat treatment. Post-hardening grinding operations should account for scale removal and final dimensional finishing.