Angle Grinder

An angle grinder is a hand-held power tool that spins an abrasive wheel at high speed on a spindle set 90 degrees to the motor. It cuts, grinds, and cleans metal, concrete, and masonry depending on the wheel fitted.

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Models

4–9 in (10.2–22.9 cm)

Wheel diameter

Brands

Cat classes

Pick a size class — capacity and reach differ across the range.

How it works

The motor drives a right-angle gearbox that turns the spindle at 8,500–11,500 RPM on common sizes. Interchangeable discs do the work: bonded abrasive wheels for cutting and grinding, flap discs for blending, wire wheels for cleaning, and diamond blades for masonry. A guard covers the rear half of the wheel and a side handle gives two-hand control against the reaction torque.

Types & variants

4-1/2 to 5 in grinders: One-handed machines for cutting rebar, weld cleanup, and work in tight spots.
6 to 7 in grinders: Two-hand tools for deeper cuts and more surface per pass in steel prep and concrete edge work.
9 in and up grinders: Heavy machines for deep cuts through thick steel, block, and pipe where small wheels cannot reach.
Cordless grinders: Battery models for mobile cutting and grinding.

Key specifications

Specification	Typical range	What it means
Wheel diameter	4–9 in (10.2–22.9 cm)	Larger wheels cut deeper and cover more surface but demand two-hand control.
No-load speed	8,500–11,500 RPM	Wheel speed rating must meet or exceed the tool's RPM.
Power source	4.5–120 V cordless or corded	Corded models sustain heavy grinding; cordless favors mobility.
Net weight	3.1–5.7 lb (1.4–2.6 kg)	Light tools reduce fatigue during overhead and vertical grinding.

How the industry sizes it

The class bands by wheel diameter. The 4-1/2 to 5 in size is for one-handed cutting of rebar and threaded rod, weld cleanup, and work in tight spots. The 6 to 7 in band offers two-hand control, deeper cuts, and more surface per pass for steel prep and concrete edge work. The 9 in and up class handles deep cuts through heavy steel, block, and pipe where a small wheel cannot reach through.

Applications

Cutting rebar, bolts, and angle iron to length
Grinding welds flat and beveling plate edges
Removing rust, paint, and coatings from steel
Cutting and notching tile, pavers, block, and concrete

Safety & operation

The wheel guard must stay fitted and positioned between wheel and operator; wheel bursts are the tool's defining hazard.
Ring-test and inspect bonded wheels before mounting, and never exceed the wheel's rated speed.
Grinding masonry releases silica dust; use a shroud with extraction, and always wear eye and face protection.

Standards & certifications

OSHA · 29 CFR 1926.303: Abrasive wheels and tools: guarding, inspection, and mounting requirements.
ANSI · B7.1: Safety requirements for the use, care, and protection of abrasive wheels.

Frequently asked

What wheel size covers most work?

A 4-1/2 or 5 in grinder handles the majority of cutting and grinding tasks; larger wheels are reserved for thick sections and large surfaces.

Can one grinder cut both metal and concrete?

Yes, by changing the disc: bonded or carbide wheels for metal, diamond blades for concrete and masonry. Guards and speed ratings must match the wheel.

Why do wheels shatter?

Usual causes are a cracked wheel, over-speed, side-loading a cutting disc, or pinching in the kerf. Inspection, correct mounting, and steady technique prevent bursts.