Angle grinder

An angle grinder is a handheld power tool with a high-speed rotating disc used to cut, grind, sand, and clean metal, masonry, and other hard materials; it accepts interchangeable wheels and accessories, includes a guard and side handle for control, and helps with tasks like trimming bolts, cutting tile, removing rust, and sharpening blades.

Angle Grinder: What It Is and How to Use It

An angle grinder is a handheld power tool that spins a disc at high speed to cut, grind, sand, or polish hard materials. The motor sits at a right angle to the spindle, which is why it’s called an “angle” grinder. By swapping the disc or attachment, you can move from cutting rebar to smoothing welds, cleaning rust, or scoring concrete pavers.

Common DIY Uses and Applications

Angle grinders handle tough jobs quickly. Typical tasks include:

  • Cutting metal: Trim bolts, cut off nails, slice through rebar, angle iron, and sheet metal using a thin cut-off wheel.
  • Grinding and shaping: Smooth welds, chamfer sharp edges, and remove burrs with a grinding wheel.
  • Surface prep: Strip rust and paint using a wire cup or wire wheel, or use a strip disc for gentler removal.
  • Masonry work: Cut concrete, brick, pavers, and tile with a diamond blade; chase grooves for conduit; or remove mortar for tuckpointing with a segmented diamond or tuckpointing wheel.
  • Sharpening: Restore mower blades, axes, and garden tools with a grinding wheel or flap disc.
  • Sanding and blending: Use a flap disc to blend welds or clean up rough metal edges without gouging.
  • Polishing: With the right backing pad and compound, polish metal surfaces. Variable speed helps prevent overheating.

Types and Variations

Angle grinders vary in size, power, and features. Key differences include:

  • Size (disc diameter):

    • 4-1/2 inch (115 mm): Most common for DIY; compact, lighter, and fits tight spaces.
    • 5 inch (125 mm): Slightly more reach and often better for flap discs and grinding.
    • 7–9 inch (180–230 mm): Heavier-duty work and deeper cuts; more weight and kickback risk.

  • Power source:

    • Corded: Consistent power, usually measured in amps or watts; good for long grinding sessions.
    • Cordless: Great mobility; measured by voltage (18V/20V) and amp-hours (Ah). Brushless motors offer better runtime and longevity.

  • Speed and control:

    • Single-speed: Fixed RPM, common for metalwork.
    • Variable speed: Useful for polishing, wood carving discs, and certain wire wheels to reduce heat and burning.
    • Electronic brake and clutch: Brakes stop the disc quickly after trigger release; clutches reduce kickback by disengaging during a bind.

  • Switch style:

    • Paddle switch (deadman): Shuts off when released; preferred for safety.
    • Slide switch: Locks on for continuous use; convenient for prolonged grinding.

Choosing the Right Angle Grinder

Match the tool to your projects:

  • Project type: For general home metalwork and light masonry, a 4-1/2 or 5 inch grinder is a smart size.
  • Power: For corded, look for 7–11 amps for DIY. For cordless, pick a platform you already own and consider 5–8 Ah batteries for longer tasks.
  • Features: Prioritize a tool-free adjustable guard, two-position or three-position side handle, spindle lock, and solid overmolded grips. Variable speed and an electronic brake are worth the upgrade.
  • Dust control: If cutting masonry, get a grinder or shroud that connects to a shop vac with a HEPA filter.
  • Ergonomics: Check balance and grip. A comfortable grinder reduces fatigue and improves control.

Wheels and Accessories You’ll Use

Always match the wheel’s size and maximum RPM rating to your grinder. Common options:

  • Cut-off wheels (thin): Fast, straight cuts in metal; use only on the edge, not the side.
  • Grinding wheels (thick): Bevels, edge shaping, weld cleanup.
  • Flap discs: Sandpaper flaps on a disc; smooths and blends without deep gouges. Pick grit based on finish (40–80 for removal, 120+ for finer work).
  • Wire wheel/cup: Rust and paint removal, cleaning weld spatter. Lower speeds reduce wire breakage.
  • Diamond blades: Continuous rim for tile, segmented for concrete/pavers, turbo for general masonry cutting.
  • Strip/clean discs: Non-woven abrasives for coating removal with less base-metal damage.
  • Backing pad with sanding discs or polishing pads: For finer finishing; variable speed helps.

Store accessories flat and dry. Discard cracked or dropped wheels.

Safe and Effective Use

Angle grinders can remove material quickly, so good habits matter.

  • PPE: Wear safety glasses and a face shield, hearing protection, gloves, and sturdy clothing. Use a respirator when grinding or cutting masonry, paint, or rust.
  • Guard on, always: Position the guard to deflect sparks away from you and bystanders. Never remove it.
  • Check the wheel: Ensure the wheel matches the grinder size and RPM, is seated correctly, and tightened just snug. Inspect for chips or cracks.
  • Secure the work: Clamp material firmly. Avoid holding small pieces in your hand.
  • Starting and cutting: Hold with two hands, let the tool reach full speed, then bring it to the work at a shallow angle. Let the wheel do the work—don’t force it.
  • Cut-off technique: Keep the disc straight; don’t twist or side-load. Plan your cut to avoid pinching; support the offcut so it can fall away.
  • Sparks and fire safety: Sparks travel far. Clear flammables, keep a fire extinguisher nearby, and check for smoldering debris when you’re done.
  • Masonry dust: Use a shroud and vacuum, or wet-cut where appropriate. Silica dust is hazardous—use a P100 or N95 respirator at minimum.
  • Wood caution: Standard cut-off and grinding wheels are not for wood. If carving wood, use dedicated wood discs on a variable-speed grinder with extra care.

Maintenance and Care

  • Clean: Blow out vents with low-pressure air and wipe the tool after dusty work.
  • Brushes and batteries: On older corded models, replace motor brushes as needed. For cordless, store batteries at moderate charge and temperature.
  • Check hardware: Inspect the flange, backing flange, and spindle threads. Replace worn flanges and damaged guards.
  • Accessory storage: Keep discs dry and protected from impacts and extreme heat.

Common Mistakes to Avoid

  • Removing the guard or side handle.
  • Using the wrong disc size or an under-rated RPM wheel.
  • Grinding on the side of a thin cut-off wheel.
  • Over-tightening the flange nut or stacking multiple discs.
  • Cutting without planning for the kerf closing and pinching the disc.
  • Setting the grinder down before the disc stops spinning.
  • Working near fuel, solvents, or sawdust piles that can catch fire from sparks.

Related Terms

  • Cut-off wheel: Thin disc for slicing metal.
  • Flap disc: Sanding-style disc for smoothing and blending.
  • Diamond blade: Grit-embedded rim for tile, stone, and concrete.
  • Wire cup/wheel: Steel or brass wires for rust and paint removal.
  • Arbor/spindle: The threaded shaft that holds the disc.
  • Paddle switch/slide switch: Trigger styles that control power.
  • Die grinder: In-line grinder for small, precise work; uses burrs instead of large discs.

Practical Examples

  • Shorten a door bolt: Clamp the bolt, fit a 1 mm cut-off wheel, score a guide line, and complete the cut with light pressure. Deburr with a flap disc.
  • Cut a patio paver: Mark the cut, use a segmented diamond blade, make a shallow scoring pass, then deepen the cut. Control dust with a shroud and vacuum.
  • Remove rust on a trailer frame: Fit a wire cup, run at moderate speed, and finish with a flap disc before priming and painting.
  • Sharpen a mower blade: Secure the blade, grind the cutting edge at the factory angle, and rebalance before reinstalling.

With the right wheel, setup, and technique, an angle grinder can speed up metal and masonry work while keeping finishes clean and edges accurate.

Back to DIY Dictionary