Starrett 6-Inch Combination Square C11H-6-4R

S. Starrett Company has been manufacturing precision measuring tools in Athol, Massachusetts since 1880.

The C11H-6-4R combination square is the benchmark against which every other combination square is measured — literally. The hardened, ground, and chrome-plated blade is accurate to within 0.

001 inches per 6 inches, a tolerance that cheaper squares cannot approach even when new. The cast iron head features a hardened steel square face ground to guaranteed squareness, with a built-in spirit level and scriber stored in the handle.

Every graduation is individually engraved, not stamped or printed, meaning the markings will remain legible after decades of shop use. Starrett sells replacement blades, scribers, and heads individually, so a damaged component never means replacing the entire tool.

Machinists, woodworkers, and toolmakers have passed these squares between generations. At roughly $130, the Starrett costs five times what a hardware store combination square does — but the hardware store square will be out of true within months.

The Starrett will still be dead accurate when your grandchildren use it. Precision tools do not depreciate; they appreciate.