An angle grinder is a compact, powerful tool that spins abrasive and cutting discs at extremely high speed. It cuts metal, grinds welds, removes rust, sharpens blades, and polishes surfaces. For anyone who works with metal — even occasionally — an angle grinder is essential. It is also one of the most dangerous power tools, so proper technique and safety gear are non-negotiable.

Angle Grinder Guide: Cutting, Grinding, and Polishing Metal

Choosing a Size

Angle grinders are measured by disc diameter:

4-1/2 inch: The standard size for home use. Compact, lightweight (4 to 5 pounds), and easy to control with one hand. Handles most cutting and grinding tasks on material up to about 1 inch thick. Price range: $30 to $80.

5-inch: Slightly larger discs mean a deeper cut and faster material removal. Compatible with many 4-1/2 inch accessories. Good middle ground.

7-inch and 9-inch: Professional and industrial sizes. Heavy, powerful, and intended for cutting thick steel, stone, and concrete. Not recommended for casual home use.

For most homeowners, a 4-1/2 inch corded or cordless grinder is the right choice. If you already own a cordless battery platform, the battery-powered version offers excellent portability.

Essential Discs and Wheels

Grinding disc: Thick (1/4 inch) abrasive disc for removing weld spatter, smoothing rough metal, and shaping. Rated for side grinding.

Cutting disc (cutoff wheel): Thin (1/16 inch or less) disc for slicing through metal pipe, angle iron, bolts, and rebar. Use only the edge — never side-load a cutting disc.

Flap disc: Overlapping abrasive flaps on a backing plate. Combines grinding and finishing in one disc. Available from 40 to 120 grit. The most versatile disc for general metalwork.

Wire wheel: Twisted or crimped wire for removing rust, paint, and corrosion. Essential for prep work on outdoor metal projects like fence hardware and gate hinges.

Diamond blade: For cutting concrete, brick, and stone. A segmented diamond blade on a 4-1/2 inch grinder handles small masonry tasks like cutting pavers.

Safety — This Is Critical

Angle grinders spin at 10,000 to 12,000 RPM. At these speeds, a disc failure sends fragments flying like shrapnel. Burns, cuts, and eye injuries are common with improper use.

Required safety gear:

Full face shield or safety glasses with side shields
Hearing protection
Leather gloves
Long sleeves
Closed-toe shoes

Safety rules:

Always use the guard. Never remove it. Adjust it to direct sparks away from you.
Inspect discs before use. Do not use cracked, chipped, or worn discs.
Use the right disc for the task. Cutting discs are for cutting. Grinding discs are for grinding. Using the wrong type can cause disc failure.
Secure the workpiece in a vise or with clamps. Do not hold it with your free hand.
Let the tool reach full speed before contacting the material.
Watch your sparks. They ignite sawdust, paper, solvents, and clothing.
Never use on wood. Wood-specific discs exist but are extremely dangerous. Use a circular saw instead.

Common Tasks

Cutting Metal

Install a thin cutting disc. Mark your cut line. With the grinder running at full speed, lower the disc straight into the material. Let the disc do the cutting — do not force it sideways. Support the workpiece so the cut does not close on the disc.

Removing Rust

A wire wheel or flap disc removes rust and old paint from metal quickly. Work methodically across the surface, keeping the grinder moving to avoid gouging.

Sharpening Garden Tools

A flap disc quickly restores the edge on lawn mower blades, shovels, hoes, and axes. Maintain the original bevel angle and work in one direction. Cool the metal in water periodically to prevent overheating.

Maintenance

Replace discs when they are worn down significantly (cutting discs should not be used below their minimum diameter)
Check the disc flanges and tightening nut for wear
Blow out the motor vents with compressed air periodically
Replace any guard that is cracked or does not lock securely

An angle grinder paired with a bench grinder gives you comprehensive metalworking capability for a combined investment under $150.