Full definition
The included opening angle of the V-shaped groove machined into a pulley, which must match the belt profile for proper wedging action. Per ISO 4183 and DIN 2211, the groove angle varies with pulley pitch diameter: smaller pulleys use narrower angles (34°) because the belt conforms more tightly to the smaller radius, while larger pulleys use wider angles (36-38°). Standard groove angles: 34° for pitch diameters up to ~190 mm, 36° for 190-300 mm, 38° for >300 mm (varies by profile). An incorrectly machined groove angle causes the belt to ride too high (angle too narrow) or bottom out in the groove (angle too wide), both reducing traction and accelerating wear. Verify groove dimensions with a pulley groove gauge. Groove sidewalls must be smooth (Ra <3.2 μm) and free of rust, oil, or scoring.