Spi 77-641-9 Square Straight Edge 18 in Spring Steel

Product Description

The SPI 77-641-9 is a square straight edge precision measuring tool used to verify flatness, check for surface irregularities, and establish reference lines on workpieces and machine surfaces. Manufactured from spring steel, it measures 18 inches in overall length, 1-13/32 inches wide, and 5/16 inches thick. Edge flatness is held to 0.0005 inches (12 micrometers) and parallelism to 0.0009 inches (24 micrometers), making it suitable for layout work and inspection tasks that demand tight tolerances. Machinists, tool and die makers, and precision fabricators rely on this type of straight edge for surface verification and scribing reference lines.

The 77-641-9 is suited for use in machine shops, fabrication facilities, and maintenance environments where reliable flatness reference is required. The spring steel construction resists deflection and maintains its geometry under normal shop conditions. It is appropriate for both bench-top layout work and in-place inspection of machine tables, surface plates, and fabricated components where a rigid, accurate straight edge is needed.

Key Features

• Edge flatness of 0.0005 inches (12 micrometers) for precise surface verification
• Parallelism tolerance of 0.0009 inches (24 micrometers)
• Spring steel construction for rigidity and durability
• 18 inches overall length covers a wide reference span
• Square edge type for consistent contact along the full edge length
• Compact profile at 5/16 inches thick for easy handling and storage

Compatibility

Designed as a general-purpose precision straight edge for use in machine shop, fabrication, and industrial inspection applications where a square-edge reference tool is required.

Installation Notes

Straight edges are handled and used by machinists and precision inspection personnel — no installation in the traditional sense applies. Clean the reference edge and the workpiece surface before use to prevent debris from affecting accuracy readings. Avoid dropping or impacting the tool, as spring steel straight edges can lose calibration if physically shocked. Store flat or in a protective sleeve to preserve edge geometry.