Spi 13-287-8 Combination Square Protractor Head

Product Description

The SPI 13-287-8 is a cast iron protractor head designed for use with combination square blade sets ranging from 12 to 24 inches in length. It mounts to the blade of a standard combination square and allows the user to measure and transfer angles with precision. The head is fully hardened and tempered for durability in demanding shop and field environments. Machinists, tool and die makers, pipefitters, and fabricators use this type of protractor head when layout and angle work demands repeatable accuracy over a range of blade lengths.

This protractor head is suited for metalworking, fabrication, and precision layout applications across both shop and field settings. It is compatible with blade lengths from 12 to 24 inches, making it a versatile addition to a multi-blade combination square set. The interchangeable design allows it to swap across popular combination square systems without modification, reducing the need for dedicated single-purpose tools on the job.

Key Features

• Cast iron construction — hardened and tempered for long service life
• Compatible with blade lengths from 12 to 24 inches
• Interchangeable with all popular makes of combination squares
• Allows angle measurement and transfer as part of a combination square set
• Weighs 0.5 pounds — lightweight enough for repeated handling during layout work

Compatibility

Designed to fit combination square blades from 12 to 24 inches in length and interchangeable with all popular makes of combination squares.

Installation Notes

This protractor head is a hand tool attachment — no power tools, wiring, or shutoff procedures are required for installation. Slide the head onto a compatible combination square blade and secure it using the locking nut or clamp screw per the blade manufacturer's instructions. Inspect the blade and head mating surfaces for debris before assembly to ensure accurate seating. Follow standard shop safety practices when working with hardened steel tools.