Choosing the right gearbox is one of the most important decisions in any drive system design. Select correctly and the gearbox runs reliably for decades; select incorrectly and you face premature failure, overheating, excessive noise or wasted energy. Yet with three main gearbox types — planetary, helical and worm — and dozens of variables, the choice can feel overwhelming.
This step-by-step guide walks you through exactly how to select the right industrial gearbox for your application, covering the key parameters and helping you decide between planetary, helical and worm gearbox types.
Step-by-Step Gearbox Selection Process
Define Your Output Torque
The single most important parameter. Calculate the torque required at the output shaft to drive your load. This depends on the force, load radius and any acceleration requirements. If you know the driven machine’s power and speed, torque (Nm) = 9550 × power (kW) / speed (RPM). Always design around the peak torque the application will demand, not just the average.
Determine the Gear Ratio
The gear ratio is the input speed divided by the required output speed. If your motor runs at 1440 RPM and you need 48 RPM at the output, your ratio is 30:1. Single-stage planetary and helical gearboxes handle low ratios (3:1 to 10:1); higher ratios need multiple stages or a worm gearbox, which achieves high ratios in a single stage.
Apply the Service Factor
Multiply your calculated torque by a service factor to account for real operating conditions. Smooth, intermittent duty uses a factor of 1.0–1.25; continuous operation with moderate shock uses 1.25–1.5; heavy shock loads or 24/7 operation use 1.5–2.0. This ensures the gearbox is sized for the real-world duty, not just the theoretical load.
Choose the Mounting Configuration
Decide how the gearbox connects to your motor and driven machine. Options include inline (coaxial input and output), right-angle (90° output), foot mount, flange mount and shaft mount (hollow-bore mounting directly on the driven shaft). The physical layout of your machine dictates this choice.
Consider Efficiency & Duty Cycle
For continuous-duty applications where energy cost matters, prioritise efficiency — helical and planetary gearboxes deliver 95–98% per stage. For intermittent or positioning duty where self-locking is valuable, a worm gearbox’s lower efficiency may be an acceptable trade-off for its holding ability.
Select the Gearbox Type
With the above parameters defined, choose the type that best fits. The comparison table below summarises when to use each. When in doubt, share your parameters with a manufacturer’s engineering team — they will confirm the optimal type and size.
Planetary vs Helical vs Worm – Which Type to Choose?
| Requirement | Best Gearbox Type |
|---|---|
| Maximum torque in minimum space | Planetary Gearbox |
| Highest efficiency, continuous duty | Helical or Planetary |
| High ratio in a single stage | Worm Gearbox |
| Self-locking (load holding) | Worm Gearbox |
| Right-angle output | Worm or Bevel-Planetary or Helical-Bevel |
| Low noise operation | Helical Gearbox |
| Precision positioning, low backlash | Planetary Gearbox |
| Lowest cost for simple low-ratio drive | Helical or Worm |
Choose a Planetary Gearbox when…
You need high torque density (lots of torque in a compact package), precision positioning with low backlash, or high efficiency for continuous duty. Ideal for robotics, cranes, mixers, and heavy industrial drives. See the planetary gearbox range.
Choose a Helical Gearbox when…
You need smooth, quiet, highly efficient power transmission for continuous operation. Helical gears run quieter than spur gears and deliver 95–98% efficiency. Ideal for conveyors, pumps, fans, cement and steel plant drives. See the helical gearbox range.
Choose a Worm Gearbox when…
You need a high reduction ratio in a single compact stage, a right-angle output, or self-locking to hold a load in position without back-driving. Ideal for hoists, lifts, conveyors and positioning applications. See the worm gearbox range.
Not Sure Which to Choose? Ask the Manufacturer
The safest way to select a gearbox is to share your application parameters — output torque, ratio, input speed, mounting and duty cycle — with an experienced manufacturer. Kavitsu Transmissions’ engineering team has selected and designed gearboxes across every major industry for 30+ years and will confirm the optimal type and size for your application, free of charge.
Checklist before you enquire: output torque (Nm), required output speed (RPM), input speed (RPM), mounting type, duty cycle (hours/day and load type), space constraints, and whether self-locking is needed. Having these ready gets you an accurate recommendation fast.
Get Expert Gearbox Selection Support
Share your application parameters and our engineering team will recommend the right gearbox type and size — with a competitive quote within 24 hours.
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