There are a number of gear types and knowing the proper nomenclature can help in requesting a price or
information on a particular gear. Below we have put together a picture gallery showing gear types and the
nomenclature for each type.

Spur gears can be hobbed or shaped. Spur gears can be cut
internal or external. The teeth are cut stright along or across the part.


Racks can be cut spur or helical. Racks look like Key stock with
teeth cut on one side. Rack can be made in different lengths and
widths. They can also be put end to end to make a rack as long as
needed.

Splines can be cut internal or external. Internal splines can be
shaped or broached. There are involute splines and key splines.
The pressure angle can vary on an involute spine.

Spur gears can be hobbed or shaped. Spur gears can be cut
internal or external. The teeth are cut stright along the part and
have parallel sides.

Sprockets are used with chain drives. They can be single row
like the one shown or multi row depending on the chain used.
Sprockets have flame hardened teeth in some cases. Sprockets
can be shaped or hobbed.

Helical gears can be cut with a right handed helix or left handed
helix like the one shown. The helix angle can be as little as 15
minutes or as much as 45°. They can be shapped or hobbed.
Internal helicals are shaped.

Bevel gears are used in right angle drivers that need some
reduction. The teeth are cut straight on the face at an angle that
will make a 90° angle. The driver and the driven gear do not have
the same number of teeth. These gears are cut on a special machine.

Spiral bevel gears are similar to bevel gears but the teeth are
cut in an ark on the face at an angle that will make 90°. A spiral
bevel runs smoother and will handle a greater load. Spiral
bevel are cut on a special machine.

Hypoid gears are similar to spiral bevels except the axis
for the diver is offset from the driven. Hypoids can be found in car
rear ends.

Miter gears are for right angle drives. The teeth are cut straight
across the face at a 45° angle. The driver and the driven have the
same number of teeth and they do not give any reduction.

Herringbone gears are cut on a Sykes or a Ferral gear shapper.
True herringbone gears have a continues tooth cut in a "V". Some
herringbone gears are cut with a small groove at the apex to
relieve the center and speed up the cutting. Most herringbone are
cut on a 30° helix.

Stager tooth gears can be shapped or hobbed. The teeth on the
right hand are cut so that the top of the tooth is lined up with
the bottom of the tooth on the left. I do not know of any advantage
to cutting a gear this way.

Double helicals are similar to a herringbone but have a wider
groove in the center. The wider groove is needed if the gear is
hobbed instead of shapped.

Worms are like a thread. They can be right hand or left hand.
They can be single start or multi start. Worms are the mate to
the worm gear.

Worm gears teeth are cut to match the radius of the out side
diameter of the worm. These gears are hobbed and are made
of brass or cast iron.