Starrett 50111 Double Square Blade 6 Inch 4R

Product Description

The STARRETT 50111 is a hardened steel double square blade designed for precision layout and measurement work in mechanical, fabrication, and trade applications. The blade measures 6 inches in length and 1 inch in width, featuring 4R graduation with four scales: 1/64 inch, 1/32 inch, 1/16 inch, and 1/8 inch. This type of blade is used with a double square head to check 90-degree and 45-degree angles, scribe lines, and verify flatness on machined or fabricated surfaces. Machinists, pipefitters, ironworkers, and sheet metal workers rely on this tool for accurate layout work in the shop or field.

This blade is suited for use in metal fabrication shops, machine shops, HVAC sheet metal work, plumbing rough-in layout, and general trade applications where repeatable square and angle references are required. The 4R graduation style provides four measurement scales on a single blade, reducing the need to switch tools during layout tasks. It is appropriate for both bench work and field use wherever a compact, precision layout reference is needed.

Key Features

• 6 inch blade length for compact, close-tolerance layout work
• 4R graduation includes 1/64 in, 1/32 in, 1/16 in, and 1/8 in scales
• 1 inch blade width provides a stable reference edge
• Hardened steel construction resists wear and maintains calibration under shop conditions
• Compatible with standard double square heads for 90-degree and 45-degree angle checking

Compatibility

Designed as a replacement or additional blade for standard double square sets accepting a 6 inch hardened steel blade with 4R graduation.

Installation Notes

This blade is a hand tool component installed by the user into a compatible double square head — no power source or electrical shutoff is required. Ensure the blade locking mechanism on the head is fully disengaged before inserting or removing the blade. Inspect the blade edges for burrs before use, as burrs can affect measurement accuracy. Handle with care to avoid bending, which will compromise squareness readings.