How to Use a Cordless Angle Grinder Safely and Effectively

Before you start: gear and safety

An angle grinder spins a thin abrasive wheel at very high speed, so protection is not optional. Wear safety glasses or a face shield, hearing protection, gloves and close-fitting clothes. Tie back long hair and remove loose jewelry.

Clear the area of anything that burns. Grinding metal throws hot sparks, and they can travel several feet. Keep paint thinner, rags, sawdust and gas cans well away, and keep a fire extinguisher nearby. Wear a dust mask or respirator when grinding rust, paint, masonry or tile, since the dust is harmful to breathe.

Clamp the workpiece firmly. Never hold a small piece in one hand while you grind it with the other.

Know your tool and pick a disc

Most cordless grinders take 4-1/2 in discs, and some also take 5 in. Compact 3 in models fit tight spots but cut shallower. Check the maximum disc size and the arbor size before you buy accessories. For example, the DEKOPRO kit fits wheels with a 7/8 inch arbor, while the Milwaukee M18 FUEL uses a 5/8"-11 spindle.

The disc must match the job. A cutting wheel is thin and made for slicing. A grinding wheel is thicker and made for removing material. A flap disc smooths and blends. Never grind sideways with a cutting wheel, because it is not built to take side load. If you are shopping for discs, see our best angle grinder disc for cutting metal page, and for garden tools, our best angle grinder disc for sharpening mower blades page.

Set up the grinder step by step

Always remove the battery before changing a disc, guard or handle. A grinder that starts by accident while your fingers are near the wheel can cause a serious injury.

• Remove the battery pack.
• Fit the guard so it sits between you and the wheel. Many guards rotate; set it so sparks and debris fly away from your body.
• Install the side handle on the left or right, depending on which hand is more comfortable.
• Press the spindle lock, then tighten or loosen the nut with the wrench. Never press the spindle lock while the wheel is spinning.
• Inspect the disc. Do not use one that is cracked, chipped or damaged, and check that its rated speed is at least the grinder's maximum speed.
• Insert the battery, hold the grinder away from your body and run it for about 30 seconds before the first cut. If it wobbles or vibrates, stop and refit the disc.

Hold it and make the cut or pass

Use both hands. One hand grips the body and the other holds the side handle. Stand with your feet apart and keep your body out of line with the wheel, so that if something breaks the pieces do not travel toward you.

Squeeze the trigger and let the wheel reach full speed before it touches the work. Many cordless models have a two stage trigger or a slide switch, so learn how yours starts. Some, like the DEWALT DCG413B, have a no-volt release so the trigger must be cycled before the tool restarts after a power interruption.

For grinding, hold the disc at roughly 15 to 30 degrees to the surface and move it back and forth with light pressure. For cutting, keep the wheel square to the line and cut steadily. Forcing the tool slows it down, overheats the wheel and raises the risk of a bind.

If the wheel binds, the grinder can kick back toward you. Features like a kickback brake or electronic clutch help, and our best angle grinder cordless page notes which models include them. They reduce the risk, but they do not replace good technique.

Cordless-specific tips

Battery tools are quiet when idle, so it is easy to forget they are live. Take the battery out whenever you set the tool down for a longer break, change accessories or carry it around.

Cordless grinders vary in weight. Models in our comparison run from 3.3 lb to 10.63 lb, with the DEKOPRO kit at 3.3 lb and the DEWALT DCG413B at 3.75 lb. A lighter tool is easier to hold overhead, but check that it comes with the guard and handle you need.

Some grinders are sold as bare tools, such as the DEWALT DCG413B and the Milwaukee 2880-20, which come without a battery or charger. Others, like the DEKOPRO and FULLYEA kits, include two batteries and a charger. If you are picking a model, our best cordless angle grinder page lays out the specs side by side.

Variable speed helps on delicate work. The FULLYEA model offers three speeds up to 12000 RPM, so you can slow down for sanding or polishing and use the top speed for cutting.

Finish up and look after the tool

When you are done, release the trigger and keep the grinder pointed away from you until the wheel stops completely. Set it down on a bench with the wheel clear of the surface, or remove the battery before you put it away.

Let hot work cool before you touch it. Metal and discs can stay hot for several minutes after grinding.

Take the battery out, wipe the dust off the vents and body, and check the disc and guard for damage. Brushless motors do not need brush changes, but vents still clog with dust. Store discs flat and dry, since damp can weaken some types.

Frequently asked questions

Can I use a cordless angle grinder without the guard?

No. The guard catches sparks and shields you if a wheel breaks. Removing it is a common cause of injury, so always fit the guard that suits the disc.

How do I know when to replace a disc?

Replace it if it is cracked, chipped, badly worn down or has been dropped. A cutting wheel that has shrunk close to the flange also needs replacing.

Is it safe to use a grinder one-handed?

Not on a full-size grinder. Use both hands and the side handle. Some compact 3 in models are designed to balance in one palm, but a firm grip and clamped work are still wise.

Can a cordless grinder cut tile or plastic?

Yes, with the right blade. Use a diamond blade for tile and a suitable blade for plastic, and match the blade to the grinder's disc size and speed.

Why does the grinder feel like it is fighting me?

Usually the disc is the wrong type, the pressure is too high, or the wheel is binding in the cut. Ease off, check the disc and let the wheel do the work.