The current industry standard, these 20° pressure angle gears have thicker, stronger teeth than 14½° pressure angle gears. They're also known as spur gears.

For smooth, quiet operation at high speeds under heavy loads, helical gears have curved teeth that engage gradually and stay in contact longer than straight teeth.

Worm gears use screw threads to reduce shaft speed by ratios of 10:1 and greater while transmitting motion at a right angle.

A former industry standard, 14½° pressure angle gears are often found on older machinery.

These plastic gears are lighter and quieter than metal gears—pair them with metal worms for lubrication-free operation. Worm gears use screw threads to make large reductions to shaft speed while transmitting motion at a right angle.