What an angle grinder is
An angle grinder is a handheld power tool with a motor that drives a spinning disc through a right-angle gearhead. It is also called a side grinder or disc grinder. The “angle” in the name refers to that right-angle head: the disc sits at about 90 degrees to the motor body, which presents the disc to the work in a convenient way.
What makes the tool so versatile is the accessory. With a grinding wheel it removes material, with a cutting wheel it slices metal or masonry, and with a flap disc or wire wheel it blends welds or cleans surfaces. For the accessory side, see our guides to grinder wheel types and cutting wheel types.
Angle grinders are commonly grouped by power source, disc size, switch design and extra features. Each is covered below.
Types of angle grinders by power source
Corded angle grinders
Corded models plug into mains power and can run as long as you need. They usually give the most sustained power for the price and have no battery to charge or replace, which makes them a common choice for workshops and long cutting or grinding sessions. The trade-offs are the cable, which can snag or become a trip hazard, and the need for a nearby outlet or a suitable extension lead.
Cordless angle grinders
Cordless grinders run on rechargeable battery packs, typically as part of a manufacturer’s battery platform (18V and 20V systems are common). They suit work on ladders, scaffolds, roofs and sites without convenient power. Runtime depends on battery capacity, the wheel and how hard you push. Heavy grinding drains a pack faster than light cutting, so many users keep a spare battery. Cordless grinders also vary in how closely they match corded power, so check the manufacturer’s specifications for the disc size you plan to use.
Air-powered (pneumatic) angle grinders
Pneumatic grinders run on compressed air. They are generally light and compact for their output, and are common in auto body and fabrication shops. They need a compressor that can supply enough air continuously, plus hoses and fittings, so they are less practical for occasional home use.
| Power source | Strengths | Limits |
|---|---|---|
| Corded | Steady power, no battery limits | Cable, needs an outlet |
| Cordless | Portable, no cable | Runtime, battery cost |
| Air-powered | Light, durable | Needs a suitable compressor and hose |
Types by disc size
Angle grinders are sold by the diameter of the disc they take. Common sizes include 4-1/2 inch (115 mm), 5 inch (125 mm), 7 inch (180 mm) and 9 inch (230 mm), and smaller mini grinders are also available.
- Small (about 4-1/2 to 5 inch): the most popular size for DIY, light fabrication and general use. Lighter and easier to control.
- Large (about 7 to 9 inch): more power and cutting depth for heavy stock removal, thick steel or masonry, but heavier and used with two hands and extra care.
Always match the wheel to the grinder. The wheel’s diameter and maximum rated speed must suit the tool, as covered in the grinder wheel guide.
Types by switch and handle
- Paddle switch: you hold the paddle to keep the grinder running, and releasing it stops the tool. Many safety guides favor this style because the tool stops if you lose control.
- Slide switch: can be locked on, which is comfortable for long cuts but means the tool keeps spinning if dropped unless it has other protections.
- Rear-handle grinders: put the grip behind the motor, a layout often seen on larger models.
- Side handle: most grinders accept an auxiliary handle, often in more than one position, which helps control.
Features that vary between models
- Variable speed: useful for polishing, sanding and working on softer materials where full speed is too aggressive.
- Brushless motors (cordless): often improve efficiency and runtime.
- Anti-restart and soft start: reduce the chance of a sudden surge or of the tool restarting on its own after a power interruption.
- Adjustable guard: the guard should stay fitted and be set to deflect sparks and fragments away from you.
- Dust shroud connections: helpful for masonry cutting when used with suitable dust extraction.
How angle grinders compare with other grinders
The phrase “types of grinders” also covers other tool families, which are different machines.
- Bench grinders: fixed to a bench, with wheels for sharpening and shaping tools.
- Die grinders: small, high-speed handheld tools for fine work with burrs and small abrasives.
- Surface grinders: precision machines for flat finishes in machine shops. They are not handheld.
- Concrete floor grinders and belt grinders: specialist tools for floors and for shaping or finishing.
Which type suits which job
| Job | Often suitable |
|---|---|
| Occasional home repairs | Small corded or cordless grinder |
| Long cutting or grinding sessions | Corded |
| Work away from power | Cordless |
| Auto body or fabrication shop with a compressor | Pneumatic |
| Heavy stock removal or thick material | Larger disc size, used carefully |
| Welders blending and cleaning welds | Small to mid-size grinder with flap discs or grinding wheels |
Safety basics
Angle grinders are among the more hazardous hand tools because the disc spins at very high speed. General practice that most manufacturers recommend:
- Wear eye or face protection, hearing protection, gloves and suitable clothing.
- Keep the guard fitted and use the correct wheel for the job and the correct rated speed.
- Inspect wheels before use and never use a damaged one.
- Let the wheel reach full speed before touching the work, and secure the workpiece.
- Follow your grinder’s manual and local safety rules.
FAQ
Why do they call it an angle grinder? Because the gearhead turns the motor’s drive through about 90 degrees, so the disc sits at an angle to the body of the tool.
Which two types of grinders are commonly used by welders? Angle grinders are the most common for weld preparation, blending and cleanup. Bench grinders are also widely used in welding shops, for example for shaping parts or sharpening tools.
What is a metal grinder used for? Removing material, shaping, deburring, blending welds, cleaning rust or paint, and, with the right wheel, cutting metal.
What are the three basic types of surface grinders? Surface grinders are a different machine from angle grinders. They are usually described by their table and spindle arrangement, such as horizontal-spindle reciprocating-table and rotary-table machines. A machining reference will give the full classification.