Starrett 50077 Combination Square Blade 4 Inch 4R

Product Description

The STARRETT 50077 is a 4-inch replacement blade for combination squares, graduated in the 4R pattern with markings at 1/64, 1/32, 1/16, and 1/8 inch intervals. It is machined from steel with a satin chrome finish that reduces glare and resists corrosion during regular shop use. At 0.63 inches wide and 0.06 inches thick, the blade fits standard combination square heads used in layout, scribing, and measurement tasks across HVAC fabrication, plumbing rough-in, electrical panel work, and general trade applications. Licensed tradespeople and skilled technicians who require precise layout work will find this blade suited for field and shop environments alike.

This blade is intended for use wherever a combination square is part of the standard toolkit. It is well suited to sheet metal shops, mechanical rooms, and job-site layout work. The 4R graduation pattern covers four common fractional scales on a single blade, making it practical for tasks that require switching between measurement increments without changing tools. It is typically used as a direct replacement when an existing blade is worn, damaged, or lost.

Key Features

• 4-inch blade length for compact layout and close-quarter measurement
• 4R graduation: 1/64, 1/32, 1/16, and 1/8 inch scales on one blade
• Steel construction for durability in shop and field conditions
• Satin chrome finish reduces glare and provides corrosion resistance
• 0.63-inch blade width and 0.06-inch blade thickness for standard combination square head compatibility

Compatibility

Designed as a replacement blade for standard combination squares that accept a 4-inch, 0.63-inch-wide blade. Verify head slot dimensions against existing hardware before installation.

Installation Notes

Installation is performed by loosening the locking nut or clamp screw on the combination square head and sliding the existing blade out before inserting the replacement. No power source or lockout procedure is required for this mechanical hand-tool component. Ensure the blade is fully seated and the locking mechanism is firmly tightened before use to prevent slippage during measurement. Inspect graduation markings for legibility before returning the tool to service.