Gear Glossary

Active profile - Is that part of the gear tooth that actually comes into contact with its mating tooth along the line of action.
Addendum - The height of the tooth above the pitch circle diameter.
Angular bevel gears - Are bevel gears in which the axes are not at right angles.
Axle - A round, hollow metal bar on which the rear wheels are mounted on.
Axial load bearing - A bearing in which the load acts in the direction of the axis of rotation.
Axial pitch - Is the distance in an axial plane surface between corresponding adjacent tooth profiles.
Axial pressure angle - Is the angle between the tangent to the tooth profile in an axial plane at the pitch surface and a line perpendicular to the axis.
Backlash - A strong and sudden reverse movement in a moving part of a machine.
Base circle - An imaginary circle used in involut gearing to generate the involutes that form the tooth profiles.
Base lead angle - Is the lead angel between the base cylinder.
Bevel gears - Are gears of conical form designed to operate on intersecting axes.
Center distance - The distance between axes of two gears in mesh.
Circular pitch - Is the distance on the circumference of the pitch circle between the corresponding points of adjacent teeth.
Circular thickness - The thickness at the point where the gear engages.
Clearence - The difference between the dedendum of one gear and the addendum of the mating gear.
Cogwheel - A wheel with a rim notched into teeth, which meshes with those of another wheel or a rack to transmit or receive motion.
Common tangent - The line tangent to the pitch circle at the pitch point.
Dedendum - The depth of the tooth below the pitch circle diameter.
Diametrical pitch - The number of teeth per one inch of the pitch circle diameter.
Differential gear - A bevel gear that permits rotation of two shafts at different speeds.
Double helical gear - Is a gear of cylindrical form with two sections of teeth that engage simultaneously with teeth of similarly designed mating gear.
External gear - The simplest gear systems with cylindrical gears and teeth parallel to the axis.
Face gear - It is a gear with cogs mortised into its face, usually in conjugation with a lantern pinion.
Face width - Is the width of the pitch surface.
Gears - It is a toothed machine part that meshes with another toothed part to transmit motion or to change speed or direction.
Gear center - Iis the center of pitch circle.
Gear box - The manual transmission on a shifter kart.
Gear ratio - It is the ratio between number of teeth of the meshing gears.
Gear train - A gear train is two or more gear working together by meshing their teeth and turning each other in a system to generate power and speed.
Helical gear - Is a cylindrical gear with helical teeth.
Idler gear - A gear wheel placed between two other gears to transmit motion from one to the other.
Involute - Is the curve described by the end of a line that is unwound from the circumference of a circle.
Internal gears - Gears that have cylindrical pith surface with teeth parallel to the axis.
Line of action - Is that portion of the common tangent to the base circles along which contact between the mating involute teeth occurs.
Line of contact - Is the line or curve along which two tooth surfaces are tangent to each other.
Miter gear - Bevel gears put together with equal numbers of teeth and axes that are usually at right angles.
Module - Is the ratio of the pitch diameter to the number of teeth.
Path of contact - The path traced by the contact point of a pair of tooth profiles.
Pawl - A mechanical device allowing rotation in only one direction.
Pinion - A small cogwheel, the teeth of which fit into those of larger gearwheel or those of a rack.
Pitch circle - Is the circle through the pitch point having its center at the axis of the gear.
Pitch diameter - Is the diameter of the pitch circle.
Pitch radius - Is the radius of the pitch circle.
Planetary gears - A device allowing several gears to orbit about others.
Pressure angle - The angle between the tooth profile at the pitch circle diameter and a radial line passing through the same point.
Rack gear - It is a gear of infinite pitch radius into which a pinion meshes.
Ratchet - A toothed wheel or bar that catches and holds a pawl, which thus prevents backward movement.
Spiral bevel gears - Designed for an angle change of 90 degrees, where the two axes are concurrent and in the same plane.
Sprockets - Are teeth like projections arranged on a wheel rim to engage the links of a chain.
Spur gear - They connect parallel shafts, have involute teeth that are parallel to the shaft and can have internal or external teeth.
Sun gear - Small gearwheel that revolves around its own axis and also around a gear meshing with it.
Velocity ratio - The ratio of the number of revolutions of the driving gear to the number of revolutions of the driven gear, in a unit of time.
Whole depth - Is the radial distance between outside circle and the root circle.
Working depth - Is the greatest depth to which a tooth of one gear extends into the tooth gear of the mating gear.
Worm gear - It is a gea with one or more teeth in the form of screwed threads.
Zerol bevel gears - Is a bevel gear with intersecting shafts.