What Hand Means
The hand of a spiral bevel gear is the direction in which its teeth lean. Look at the face of the gear, with the teeth towards you. If the outer end of a tooth leans to the right of the tooth's centre line, the gear is right hand; if it leans to the left, the gear is left hand.
Mating Gears Have Opposite Hands
A pinion and its gear always have opposite hands. If the pinion is left hand, the gear is right hand.
Why Hand Matters
The hand and the direction of rotation together decide whether the pinion pushes into the mesh or away from it. A thrust that pushes the pinion out of mesh is easier on the setting; a thrust that draws it in can reduce backlash under load, so many designers choose the hand so that the thrust pushes away. Bearings must carry the thrust in either case.
How to Tell the Hand of a Gear
Hold the gear with its teeth towards you and look at which way the teeth lean, as above. For a quick check, remember that the mating gear must be the opposite hand.
When Ordering
State the hand of the pinion and the direction of rotation, or send the old set. If you only have the gear, tell us and we work out the pinion. See how to measure a worn gear and custom spiral bevel gears.
