The Simonds triangular hand file, also known as a three square file, has a triangular shape with double-cut, variable-pitch American pattern teeth for filing angles, grooves, corners, and dies. The file tapers slightly toward the point to ease access into grooves. It has double-cut American pattern teeth on all sides for rapid material removal, and the teeth are variably pitched to help reduce chattering and prolong tool life. The tang can be used with an optional handle for secure gripping (sold separately).
Hand files are used to remove material and smooth and shape workpieces. They have forward-facing cutting teeth and cut when pushed over either a stationary or rotating workpiece. Single-cut teeth are single rows cut diagonally across the width of the file. Double-cut teeth have two sets of rows cut in opposite directions. American pattern files have three coarseness grades. Coarse, also known as bastard cut, is suitable for efficient, heavy material removal where finish is not a concern. Medium, also known as second cut, offers average material removal and finish quality. Fine, also known as smooth cut, provides the smoothest finish. Swiss pattern files have eight coarseness grades, from 00 (coarse), 0 (medium), and 1 to 6 (fine to finest), offering a smoother finish than equivalent American pattern files. For Swiss pattern files the length of the tool is the length of the blade, not counting the tang, which is the pointed end fitted for a handle; for American pattern files the length of the tool is its entire length, including the tang.
Simonds International manufactures tools for cutting and finishing. The company, founded in 1832, is headquartered in Fitchburg, MA.