Spi 13-231-6 Precision Parallel Set 9x1x0.75 in Steel

Product Description

The SPI 13-231-6 is a matched pair of hardened steel precision parallels used in machining, grinding, and inspection setups to establish accurate reference planes and support workpieces at a consistent height. Each parallel measures 9 inches long, 1 inch high, and 0.75 inches thick, with all four faces precision ground to a parallelism tolerance of 0.0003 inches and a squareness tolerance of 0.0005 inches. Hardened to 50 Rc, these parallels maintain dimensional stability under the clamping forces and cutting loads typical in milling and surface-grinding applications. Machinists, tool-and-die makers, and precision metrology technicians are the primary users.

These parallels are suited for use on surface plates, in vises, and on magnetic chucks where a flat, square reference surface is required. The four-face ground construction gives the user multiple usable orientations, increasing setup flexibility. At 9 inches in length, they accommodate a wide range of workpiece sizes commonly encountered in job-shop and production machining environments. The matched-pair format ensures consistent stack height when both parallels are used simultaneously to support a single workpiece.

Key Features

• Parallelism tolerance of 0.0003 inches across all four precision-ground faces
• Squareness tolerance of 0.0005 inches for reliable right-angle reference setups
• Hardened to 50 Rc for wear resistance and long-term dimensional stability
• Four-face ground construction allows multiple orientations in a single setup
• Sold as a matched pair to ensure uniform support height on both sides of a workpiece
• High-grade hardened tool steel construction throughout

Compatibility

Designed as a general-purpose precision parallel set compatible with standard milling vises, surface grinders, and surface plate inspection setups requiring a 1-inch workpiece elevation with a 9-inch support span.

Installation Notes

Parallels should be handled with care to avoid nicking ground surfaces, which can degrade reference accuracy. Clean the vise bed, magnetic chuck, or surface plate contact area before placing parallels to prevent chips or debris from causing tilt errors. No special tools are required for placement, but a test indicator is recommended to verify seating before clamping a workpiece. Store parallels in a protective case or on a padded surface to prevent contact damage between setups.