Gearbox Guides: Worm, Planetary, and Bevel Gearboxes

Gearboxes in Mechanical Engineering: An Overview

Gearboxes transmit torque, convert speeds, and match drive machines to driven machines. Choosing correctly between worm, planetary, bevel, or spur gearboxes determines efficiency, service life, and total system cost.

Quick Orientation

High efficiency and compact design → Planetary gearbox. Self-locking and angular offset → Worm gearbox. 90° axis offset with high load → Bevel gearbox.

The Most Important Gearbox Types

Worm Gearboxes

Worm gearboxes consist of a helical worm and a worm wheel. They enable large gear ratios in a single stage (i = 5 to 100) and are self-locking at high ratios. Efficiency typically ranges from 40 to 90 % — depending on lead angle and lubrication.

Planetary Gearboxes

Planetary gearboxes achieve efficiencies of 95–98 % per stage and transmit torque through multiple simultaneous tooth engagements. The result: high power density in a compact package. Typical gear ratios: i = 3 to 10 per stage, up to i = 1000 in multi-stage configurations.

Bevel Gearboxes

Bevel gearboxes enable power transmission between intersecting axes — typically at 90°. Spiral-toothed bevel gears run more quietly than straight-toothed ones and are suited for higher speeds and loads.

Comparison: Efficiency and Gear Ratio

Gearbox Type	Efficiency	Gear Ratio i	Self-Locking
Worm Gearbox	40 – 90 %	5 – 100	✓ (at small lead angle)
Planetary Gearbox	95 – 98 %	3 – 10 (per stage)	–
Bevel Gearbox	95 – 98 %	1 – 6	–
Spur Gearbox	97 – 99 %	1.25 – 6 (per stage)	–

Selection Criteria at a Glance

Required gear ratio: Large i (> 20) in a single stage → worm gearbox; small i → spur or planetary gearbox
Efficiency: Energy-intensive continuous operation → prefer planetary or spur gearboxes
Self-locking: Holding loads without a brake → worm gearbox with sufficiently small lead angle
Shaft orientation: 90° angle → worm or bevel gearbox
Package size: Compact at high torque → planetary gearbox

Note on Sizing

For a definitive gearbox selection, we recommend contacting our application engineers directly. We will size the optimal gearbox based on your load, speed, and installation data.