Helical & Spur Gear

Operating principles and characteristics

Spur gear teeth run parallel to the shaft. Parallel-axis helical gears engage progressively along inclined teeth, supporting greater continuity of contact. Single-helical gears generate axial thrust and need suitable bearing support. Both require assessment of tooth-root strength and contact fatigue.

Applications and operating conditions

Spur gears commonly provide parallel-shaft reduction, roller synchronization, feeding and general machine drives. Helical gears serve reducers, machine tools and conveying drives requiring smoother continuous operation. Packaging and food-processing mechanisms, and sun and planet gears in planetary reducers, may use spur or helical teeth according to design. Compare center distance, ratio, backlash, noise and efficiency; helical gearing also requires axial-thrust and bearing checks.

Selection and drawing checklist

Distinguish normal from transverse module on the drawing. Specify pressure angle, helix angle and hand, center distance, backlash and accuracy. Equal numerical modules do not guarantee compatibility across systems. Also discuss heat-treatment distortion and finishing requirements.

Technical question