What Is an Angle Grinder?
An angle grinder is a handheld power tool that spins an abrasive disc or cutting wheel at very high RPM — typically between 7,000 and 12,000 RPM depending on the disc size. It's one of the most versatile tools in metalworking, construction, and fabrication, capable of grinding, cutting, polishing, and surface preparation.
The most common sizes are 4-1/2 inch and 5 inch for general use, with larger 7-inch and 9-inch models used in heavy industrial applications.
What Can You Do with an Angle Grinder?
- Cut metal: Rebar, steel pipe, sheet metal, bolts
- Grind and smooth welds: Flush out weld beads after welding
- Remove rust and paint: Surface preparation before painting or coating
- Sharpen tools: Axes, lawnmower blades, chisels
- Cut tile and masonry: With the right diamond disc
- Polish metal: With a polishing disc and compound
Choosing the Right Disc
The disc you use determines what your angle grinder can do. Never use a disc rated for a lower RPM than your tool's maximum speed — this is a serious safety hazard.
| Disc Type | Use Case |
|---|---|
| Grinding disc (metal) | Smoothing metal, removing material |
| Cutting disc (metal) | Cutting steel, rebar, bolts |
| Diamond cutting disc | Tile, concrete, stone, masonry |
| Flap disc | Grinding and finishing in one step |
| Wire cup/wheel | Rust removal, paint stripping |
| Polishing pad | Metal polishing and buffing |
Safety: Non-Negotiable Rules
Angle grinders cause a disproportionately high number of serious workshop injuries. Respect these rules every single time:
- Always wear a face shield — not just safety glasses. Disc fragments travel at extreme velocity.
- Use the side handle. Always attach and use the auxiliary handle for two-handed control.
- Keep the guard in place. The disc guard is not optional — it deflects sparks and fragments away from you.
- Inspect discs before use. Never use a cracked, chipped, or damaged disc. Discard immediately.
- Never use a disc rated below your tool's RPM. A disc rated for 8,000 RPM on a tool spinning at 11,000 RPM can shatter explosively.
- Let the tool reach full speed before contact. Apply disc to material gradually — never jam it in.
- Secure your workpiece. Use clamps — never hold material with your hand while grinding.
- Be aware of kickback. If the disc catches or binds, it can violently throw the tool. Maintain a firm grip at all times.
Corded vs. Cordless Angle Grinders
Corded grinders deliver consistent, high power ideal for extended grinding sessions. For most cutting and grinding tasks, a corded 7–9 amp, 4-1/2" model is the workhorse choice. Cordless models have improved with higher-voltage batteries and are excellent for remote work or quick cuts — but for sustained heavy grinding, corded still has the edge.
Final Thoughts
The angle grinder earns its place in any serious tool collection. It's fast, powerful, and incredibly versatile — but it demands respect. Master the safety basics, choose the right disc for your task, and this tool will handle some of the toughest jobs in your shop or on the jobsite with impressive efficiency.