Chainsaw chain, rim sprocket and sharpening file sizing guide

Ordering the right replacement saw chain, floating rim sprocket or round sharpening file comes down to four stamped numbers on your guide bar and drive links: pitch, gauge, drive link count, and spline bore diameter.

1. Understanding Drive Link Gauge Stamps (#3 vs. #6)

Look closely at the tang of your drive links. A stamped '3' indicates a .050 in. (1.3 mm) gauge drive link, while a stamped '6' indicates a .063 in. (1.6 mm) gauge drive link. The gauge must match your guide bar groove width.

2. Rim Sprocket Bore Sizes: Small 7-Spline (20 mm) vs. Large 7-Spline (23 mm)

A 3/8-7 rim sprocket comes in two spline bore sizes, both with a 35 mm outer diameter: the Small 7-Spline (SD7) has a 20 mm inner bore and 6 mm thickness, while the Standard 7-Spline (Large Hole) has a 23 mm inner bore and 7.5 mm thickness. Always measure your clutch drum spline before ordering.

3. Matching Round File Diameter to Chain Pitch

Use a 5/32 in. (4.0 mm) round file for 1/4 in. and 3/8 in. Low Profile Picco chains; a 3/16 in. (4.8 mm) file for .325 in. pitch chains; and a 13/64 in. (5.2 mm) or 7/32 in. (5.5 mm) file for standard 3/8 in. full-chisel chains.