Precision Brand 56504 Mill Stock Key Stock 5/16x5/16x12 in

Product Description

The PRECISION BRAND 56504 is a mill stock key stock bar cut to 0.3125 x 0.3125 x 12 inches, manufactured from low-carbon steel to ASTM A108 specifications. Each piece carries a Rockwell B80-90 hardness rating, making it suitable for standard power-transmission keyway applications. The plain finish is ready for installation as-received or can be cut to length on-site. This package includes six pieces, providing enough stock for multiple jobs or a single multi-key assembly. Machinists, millwrights, and maintenance technicians are the typical installers.

Mill stock key stock in this 5/16-inch square profile is commonly used in light to medium industrial drive assemblies, including motors, gearboxes, pumps, fans, and conveyor shafts. The square cross-section mates with standard 5/16-inch keyways on both the shaft and the hub, transmitting torque between rotating components. It is used across residential HVAC equipment, commercial pump sets, and general industrial machinery wherever a removable, replaceable torque-transfer connection is required.

Key Features

• Low-carbon steel construction to ASTM A108 for consistent mechanical properties
• Rockwell B80-90 hardness for reliable torque transmission in standard keyway applications
• 5/16 x 5/16 x 12-inch square mill stock profile fits standard keyways without additional machining in most cases
• Plain finish — ready to cut, file, or install as-received
• Six pieces per package, minimizing trips to supply for multi-key jobs

Compatibility

Designed as an OEM-style replacement or service stock for any shaft and hub assembly with a standard 5/16-inch square keyway, consistent with ASTM A108 low-carbon steel key stock specifications.

Installation Notes

Key stock installation is typically performed by a millwright, maintenance technician, or experienced mechanic. Always de-energize and lock out the drive equipment per OSHA lockout/tagout procedures before removing or installing key stock. Cut the stock to the required length using a cold saw, angle grinder with cutoff wheel, or bandsaw, and deburr all cut edges before fitting. Do not force an oversized key into a keyway, as this can damage the shaft or hub bore.