Manufacturer of: herringbone gears, helical gears, spur gears, bevel gears, planetary gears, worm gears and rack & pinions


We hope this glossary of terms adds to your understanding of Summit Gearworks and the power transmission and gear industry. 

We have included images of the various Gear Types, definitions of Pitch Types and Other Gear Terms.

Gear Tooth Profile and Definitions





The distance a tooth projects above, or outside of, the pitch line or circle Up


The amount by which the width of a tooth space exceeds the thickness of the engaging tooth on the operating pitch circles. Up

Bottom Land

The root diameter Up

Chordal Addendum

The distance from the outer diameter to the pitch line Up

Chordal Thickness

The tooth thickness at the pitch line Up

Circular Pitch

The distance from the centre of one tooth to the centre of the next tooth measured round the circumference of the pitch circle. Up


The amount by which the dedendum of a gear tooth exceeds the addendum of a mating gear Up

Center Distance

The distance from the centre of the gear shaft to the centre of the pinion shaft Up


The depth of a tooth space below, or inside of, the pitch circle Up

Pitch Diameter

The diameter of the pitch circle Up

Pressure Angle

The angle between a tooth profile and a radial line at its pitch point Up

Tooth Fillet

The radius where the bottom land meets the tooth flank Up

Top Land

The outer diameter of the gear Up

Tooth Profile

The involute curve of a  gear tooth Up

Whole Depth

The total height of a tooth or the   total depth of a tooth space Up

Working Depth

The depth of tooth engagement of two mating gears. It is the sum of the addendums. Up



Helical Angle

The angle that a helical gear tooth makes with the gear axis at the pitch circle Up


Please click on the gear term to view the corresponding definition.

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