Types of Gears: A Simple Guide

What Are Gears?

Gears are round parts with teeth. These teeth help move power from one turning part to another. Gears help machines work by:

• Moving power from one spot to another
• Making things turn faster or slower
• Changing the direction things turn

Gears are in many things you see every day like cars, clocks, and bikes!

7 Main Types of Gears

Let’s look at the big types of gears and what makes each one special!

1. Spur Gears

Spur gears have straight teeth that stick out. They are the most common type of gear.

• What they do: Move power between parts that run side by side
• Where you find them: Clocks, toy cars, and moving walkways
• Good things: Work very well (85-98% efficient)
• Not so good: Can be noisy

Fun fact: About 65% of all gear systems in factories use spur gears! 

2. Helical Gears

Helical gears have teeth that go at an angle. They look like they twist around the gear.

• What they do: Move power smoothly and with less noise
• Where you find them: Car parts and water pumps
• Good things: 20% stronger than spur gears and 6-12 dB quieter
• Not so good: Push sideways while turning

Toyota cars use helical gears to make their hybrid cars run more quietly. 

3. Bevel Gears

Bevel gears look like cones with teeth. They help turn power around corners.

• What they do: Change turning direction by 90 degrees
• Where you find them: Hand drills and car parts
• Good things: Turn power around corners
• Not so good: Hard to make

Helicopters use special bevel gears to help move their big blades! [^4] You can see bevel gears made with precision CNC milling when very exact parts are needed.

4. Worm Gears

Worm gears have a screw shape that turns a wheel. They look different from other gears!

• What they do: Slow down turning a lot (up to 100:1 ratio)
• Where you find them: Elevators and big machines
• Good things: Can stop things from moving backward
• Not so good: Can waste some power as heat

Elevators use worm gears as safety devices that stop them from falling down! 

5. Rack and Pinion

A rack and pinion has a straight bar with teeth and a small round gear.

• What they do: Turn spinning motion into straight-line motion
• Where you find them: Car steering and some machines
• Good things: Simple design
• Not so good: Need good setup to work well

6. Planetary Gears

Planetary gears have a center “sun” gear with smaller “planet” gears going around it.

• What they do: Change speed a lot in a small space
• Where you find them: Wind turbines and cars
• Good things: 3 times more powerful than other gears in same space
• Not so good: More complex

Wind turbines use planetary gears to turn the slow movement of big blades into fast spinning for making power.  Planetary gears often need custom metal machining to work right.

7. Internal Gears

Internal gears have teeth on the inside of a ring instead of the outside.

• What they do: Help make planetary systems work
• Where you find them: In planetary gear sets
• Good things: Save space
• Not so good: Hard to make

Special Gear Types

There are some special gears for certain jobs:

• Hypoid Gears: Used in cars to make them run 15% better on gas
• Herringbone Gears: Double helical teeth that don’t push sideways
• Spline Gears: Special shape to lock onto shafts
• Magnetic Gears: Work without touching (used in robots)

Choosing the Right Gear Type

How do you pick the best gear? Think about these things:

Key Things to Think About:

For Different Jobs:

• Cars: Use hypoid and planetary gears
• Air planes: Use light, strong bevel gears
• Robots: Need precise spur and magnetic gears

Companies that make robots need precision grinding services for their gears.

Gear Materials

Gears can be made from many different things:

• Metal: Steel, iron, brass, bronze
• Plastic: Nylon, acetal, POM
• Other: Carbon fiber, wood (for some things)

Why Material Matters:

• Steel gears are very strong but heavy
• Plastic gears are quiet but not as strong
• Bronze gears work well with steel and help reduce friction

For plastic gears, CNC plastic machining gives good results.

How Gears Are Made

Gears need to be made very precisely. They are made by:

• Cutting: Using special machines to cut teeth
• Heat treating: Making metal harder
• 3D printing: For plastic gears and test parts

Gear Problems and Fixes

Gears can have problems. Here are some common ones:

• Noise: Use helical gears or better lubrication
• Wear: Pick harder materials or better surface finish
• Breaking: Don’t put too much force on the gear

Gear Standards

Gears follow special rules so they work together:

• ISO 1328: Rules for how exact gears must be
• AGMA 2000: Rules for how much load gears can take
• DIN 3961: Rules for gear tolerances

More than 70% of industrial gears follow these rules. 

Questions People Ask

What is the strongest type of gear?

Spur and helical gears made from hardened steel are strongest for most jobs.

Which gear type is best for high speed?

Precision-ground helical gears work best at high speeds because they run smoothly.

How can I make gears quieter?

Use helical or herringbone gears and keep them well lubricated.

What makes gears break?

Bad alignment, poor lubrication, or putting too much force on them.

Summary

Gears are amazing parts that help machines work. From the simple spur gear to complex planetary systems, each type has a special job.

• Spur gears are simple and common
• Helical gears are quieter
• Bevel gears turn corners
• Worm gears slow things way down
• Rack and pinion gears make straight movement
• Planetary gears pack lots of power in small spaces
• Internal gears work from the inside out

Next time you hear a machine working, think about the gears inside making it all happen!