When a shaft has to turn a corner, most engineers reach for either miter gears or bevel gears. They look related because they are: both transmit power between intersecting shafts, both are typically mounted at 90 degrees, and both are cut with the same tooth-form systems. But they solve different problems, and choosing the wrong one is a common failure mode in rebuilt or replacement drives.
Miter gears: the fixed 1:1 right-angle drive
Miter gears are used as right-angle drives transmitting power between intersecting shafts at a fixed 1:1 ratio. They are the go-to when the goal is simply to change the direction of rotation without changing speed. Only miters of the same number of teeth, pitch, and pressure angle can be operated together, and more than two miters may be used in sets — for example, in a differential.
Two details matter on installation. First, the thrust of miter gears causes the gears to separate, so ball or roller bearings should be used rather than sleeve bearings, and thrust bearings should be used to absorb backward thrust. Second, all standard stock miter gears must be mounted at right angles (90 degrees) for proper tooth bearing. Most stock miters are manufactured from 1144 carbon steel, offered as unhardened (M series), hardened teeth (HM), or hardened teeth with keyway and setscrew (HMK). Hardened miter gears have roughly 50% more horsepower capacity and provide greater wear resistance than untreated gears.
Bevel gears: right angle plus a ratio
Bevel gears cover the same right-angle geometry but are stocked in ratios from 1:1 to 6:1. That makes them the choice when you need to change both direction and speed in one component — for example, driving a higher-speed or lower-speed shaft off a right-angle input.
Bevel gears are cut with the long-and-short addendum system and a 20-degree pressure angle to compensate for tooth undercut in gears and pinions with low numbers of teeth. Like miters, most are cut with the coniflex tooth form, which allows a slight misalignment at assembly and during operation — a real advantage on equipment with worn housings or flexible mounting. Mounting distance must still be held to maintain proper backlash and keep the ends of the teeth flush with each other.
A straight mineral oil note
For most miter and bevel gear applications, a straight mineral oil is the recommended lubricant. Splash or forced lubrication keeps the tooth mesh cool and carries away wear particles — a simple step that extends gear life dramatically, especially on hardened-tooth sets where lubrication quality matters most.
Whether you need a fixed 1:1 miter set or a bevel set with a specific ratio, send us the number of teeth, pitch, pressure angle, and bore requirements. We will match a stock set and confirm the mounting arrangement before you order.
Catalog item plug: RBC Industrial stocks Martin miter and bevel gears in the 20-degree pressure angle system, including M (unhardened), HM (hardened), and HMK (hardened with keyway) series.