Full definition
A V-belt pulley with a mechanically adjustable pitch diameter, allowing fine-tuning of the output speed on an existing drive without changing pulleys. The adjustment mechanism typically uses a threaded hub or set-screw arrangement to move one flank relative to the other, changing the effective groove width and thus the diameter at which the belt rides. Typical adjustment range: ±15-20% of nominal pitch diameter. The belt must be re-tensioned after each adjustment. Used in HVAC fans (balancing airflow), centrifugal pumps (fine-tuning flow rate), textile machines, and test benches where precise speed matching is needed. Limited to single-belt drives and moderate power. Not suitable for high-torque or shock-load applications. Brands: TB Woods, Browning, Maurey. Per ISO 4183 for groove dimensions. Requires a standard V-belt, not a special variable-speed belt.