Starrett 51451 Four Face Tool Steel Parallel 6in Matched Pair

Product Description

The STARRETT 51451 is a four-face precision-ground parallel made from a special grade of tool steel. Sold as a matched pair, these parallels measure 6 inches long, 1/2 inch high, and 3/8 inch thick. All four faces are accurately ground to close limits, delivering a squareness tolerance of 0.0005 inches per 1 inch. Machinists, toolmakers, and setup technicians use precision parallels to support and locate workpieces at a consistent, repeatable height during machining, grinding, and inspection operations. The four-face design increases versatility by providing multiple usable reference surfaces.

Four-face parallels like the 51451 are standard equipment in machine shops, toolrooms, and manufacturing environments. They are used to elevate workpieces in vises or on surface plates, ensuring parts are held square and at the correct elevation before milling, grinding, or layout work. The matched-pair configuration allows left and right support of a workpiece at identical heights, which is critical for maintaining parallelism and preventing rocking or tilting during fixturing.

Key Features

• All four faces precision ground to close limits for consistent reference surfaces
• Squareness tolerance of 0.0005 inches per 1 inch
• Manufactured from a special grade of tool steel for durability and wear resistance
• Sold as a matched pair for symmetric workpiece support
• Compact profile at 1/2 inch high and 3/8 inch thick suits tight vise setups

Compatibility

Designed as a general-purpose precision parallel for use with milling vises, surface plates, and grinding fixtures in toolroom and production machining applications.

Installation Notes

Parallels are handled and placed by machinists and toolmakers — no power tools or fasteners are required for use. Surfaces should be clean and free of chips or burrs before placing parallels in a vise or on a surface plate, as contamination will compromise accuracy. Inspect the parallel faces periodically for nicks or wear that could affect ground tolerances. Store pairs together to preserve matched dimensions.