Starrett 56991 O1 Tool Steel Flat Stock 5/16x1-1/4x18 in

Product Description

The STARRETT 56991 is an O1 oil-hardening tool steel flat stock bar used in toolmaking, die work, jig fabrication, and precision machining applications. Manufactured to AISI Type O1 specification, this flat bar measures 5/16 inches thick, 1-1/4 inches wide, and 18 inches long, with a weight of 1.99 pounds. Thickness and width tolerances are held to +0.0100 to +0.0150 inches, and length tolerance is +0.2500 inches. Edge squareness is held to 0.003 inches per inch across all edges. O1 tool steel is a general-purpose oil-hardening grade known for good machinability in the annealed state and consistent response to heat treatment.

This flat stock is suited for machinist shops, tool-and-die operations, and maintenance environments where close-tolerance steel bar stock is needed for custom tooling, punches, dies, blades, or gauges. The 18-inch length is a standard cut suitable for bench machining or further parting on a metal-cutting saw. Licensed machinists and tool-and-die makers are the primary users of this material. It ships in annealed condition, ready for machining prior to hardening and tempering.

Key Features

• AISI Type O1 oil-hardening tool steel — good machinability in annealed state, consistent hardening response
• Thickness: 5/16 inches with tolerance of +0.0100 to +0.0150 inches
• Width: 1-1/4 inches with tolerance of +0.0100 to +0.0150 inches
• Length: 18 inches with tolerance of +0.2500 inches
• Edge squareness held to 0.003 inches per inch on all edges
• Weight: 1.99 pounds per piece

Compatibility

Designed as a standard O1 oil-hardening tool steel flat bar for use in toolmaking, die making, and general precision machining applications requiring AISI Type O1 material specification.

Installation Notes

This is raw bar stock material worked by machinists and tool-and-die makers using standard metal-cutting and grinding equipment. Material is supplied in the annealed (soft) condition and must be heat treated by a qualified professional to achieve desired hardness after final machining. Follow established shop safety practices when cutting, grinding, or machining tool steel. Heat treatment should follow AISI O1 recommended procedures for hardening temperature, quench medium, and tempering cycle.