Starrett 66682 Combination Square Set 12 in 4 Piece

Product Description

The STARRETT 66682 is a 4-piece combination square set built for layout, inspection, and measurement work across mechanical, fabrication, and trade applications. The set includes a 12-inch hardened steel blade with 4R graduation, meaning the blade is marked in 1/16, 1/32, 1/64, and 1/8 inch increments for precise measurement at multiple resolutions. Three interchangeable cast iron heads are included: a square head, a center head, and a protractor head. Together they allow the same blade to perform right-angle layout, center-finding on round stock, and angle measurement without swapping tools. The set weighs 2 pounds and is suited for machinists, pipefitters, sheet metal workers, and general mechanical tradespeople.

This combination square set is used in shops, fabrication environments, and field service work where accurate layout and inspection are required. The 4R graduation system provides four scales on a single blade edge, reducing the need to switch measuring tools mid-task. The protractor head allows direct angle transfer and setting. The center head is commonly used when locating the center of cylindrical stock. Residential and light commercial trades such as HVAC sheet metal, plumbing rough-in layout, and electrical panel work benefit from having all three head types available in one kit.

Key Features

• 12-inch hardened steel blade for durability and long-term accuracy
• 4R graduation: 1/16, 1/32, 1/64, and 1/8 inch increments on a single blade
• Three cast iron heads included: square, center, and protractor
• Interchangeable head design allows one blade to serve multiple layout functions
• Cast iron head construction resists wear under repeated shop use
• Compact 2-pound total weight for easy transport and bench use

Compatibility

Designed as a general-purpose combination square set suitable for machinists, fabricators, and trade professionals requiring 4R-graduated layout and inspection tools.

Installation Notes

No installation is required for this hand tool. Before use, verify the blade is fully seated and the head locking nut is snug to prevent blade shift during measurement. When using the protractor head for angle transfer, confirm the workpiece surface is clean and flat to avoid reading error. Store the set in a dry location to prevent rust on the hardened steel blade and cast iron heads.