How to Use an Angle GrinderUpdated: Oct. 02, 2018
Angle grinders are versatile tools that can grind metal and cut tile, stucco and pavers, rout out mortar, plus they can sand, polish and sharpen.
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- An hour or less
- Less than $20
Overview of angle grinders
You’ll find angle grinders anywhere power tools are sold. Larger hand grinders are available, but the popular 4-in. and 4-1/2 in. grinders are the right size for most tasks. You can buy very inexpensive angle grinder tool, but for frequent use or for demanding jobs like cutting stucco or cement, I’d recommend spending a little more for a grinder with a more powerful motor (look for a motor that draws 5 to 9 amps).
The ability to handle different wheels and accessories is what makes angle grinders so versatile. Your angle grinder includes a spindle washer and spindle nut that you’ll install in different configurations to accommodate thicker or thinner wheels or remove altogether when you screw wire wheels and cups onto the threaded spindle. Consult your manual for instructions on mounting wheels and accessories.
You’ll find abrasive wheels for an angular grinder in any hardware store or home center. Although the wheels all look similar, they’re designed for different tasks. Read the labels.
Photo 1: Use a wire brush for cleaning
Clean rust and caked-on cement and dirt from garden tools with a wire cup. Secure the work with clamps or a vise. Make sure the brush is spinning away from, not into, the edge. Otherwise, the brush can catch on the edge and cause the grinder to kick back at you.
Photo 2: Paint removal
Remove paint with a wire wheel. Again, be careful to work away from, not into, sharp edges. Wire wheels fit into crevices and tight areas.
Wire wheels remove rust and flaking paint quickly. Wire wheel and brush angle grinder attachments are designed for different types of stripping, cleaning and deburring tasks. Wire cup brushes work best for stripping paint or rust from broad, flat areas. Wire wheels fit into crevices and corners more easily. Wheel and brush attachments come in a wide variety of styles. Read the packaging to find one that works for your application. Also, make sure to match the threads to the spindle threads on your grinder. Most angle grinders have 5/8-in. spindle threads, but there are a few oddballs.
Cut bars, rods and bolts
Photo 3: How to cut rebar
Mount a metal cutoff wheel in your angle grinder. Prop up the long side of the rebar and hold it securely. Drop the cutoff wheel through the metal, allowing the weight of the tool to do most of the work. Allow the short end to drop freely to avoid binding the blade.
Photo 4: Cut frozen bolts
Grind bolts flush to concrete. You can brush against the concrete, but don’t try to cut into it with this wheel.
If you’re patient, you can cut most metal with a hacksaw. But for quick, rough cuts, it’s hard to beat a grinder. I’ve used an angle grinder to cut rebar (Photo 3), angle iron, rusted bolts (Photo 4) and welded wire fencing. Use an inexpensive cutoff wheel for these and other metal-cutting tasks.
Cut tile, stone and concrete
Photo 5: Score the tile face
Mark the outline of the cut accurately on both the front and the back of the tile. Clamp the tile to your workbench and score the outline about 1/8 in. deep on the front with the diamond blade.
Photo 6: Finish the cut on the back
Flip the tile over and cut through the tile from the back. Extend the cuts slightly past the lines at the corners to make crisp, square corners.
Notching and cutting ceramic or stone tile to fit around outlets and other obstructions are difficult if not impossible with standard tile cutters. But an angle grinder fitted with a dry-cut diamond wheel makes short work of these difficult cuts.
Restore cutting edges
Photo 7: Sharpen blades
Clamp the blade in a vise or to your workbench with hand clamps. Orient the grinder and adjust the blade guard to deflect sparks from your face and body. Align the grinding wheel with the angle on the blade. Start the grinder and move the grinding wheel steadily across the blade while applying light pressure.
Outfitted with a grinding wheel, an angle grinder is a great tool for restoring edges on rough-and-tumble tools like hoes, shovels and ice scrapers or for the initial grinding of axes, hatchets and lawn mower blades. If you need a sharper edge than the grinder leaves, follow up with a mill bastard file. Photo 7 shows how to sharpen a lawn mower blade. Use the same technique to restore the edge on other tools. Orient the grinder so that the wheel spins from the body of the blade toward the edge (refer to the arrow on the body of the grinder to determine which direction the wheel spins).
Finally, with the grinder off, rest the grinding wheel against the blade and adjust the angle of the grinder to match the blade’s bevel. This is the position you’ll want to maintain as you grind the edge. Lift the grinder from the edge, switch it on and let it come to speed before moving it into the blade.
Stroke the grinder across the work in the direction of the handle rather than grinding back and forth. Then lift it off and repeat, concentrating on holding the grinder at a consistent angle throughout the stroke.
It’s easy to overheat a metal blade with a grinder. Overheated metal turns a bluish black or straw color and won’t stay sharp for long. To avoid overheating, apply only light pressure and keep the grinder moving. Also, keep a bucket of water and sponge or rag handy and drench the metal frequently to keep it cool.
Cutting out old mortar
Photo 8: Grind mortar
Grind out old, loose mortar with an angle grinder and diamond tuckpointing wheel. Make two or three 1/2-in. deep passes to completely clear the joint. Stay about 1/8 in. from the brick to avoid damaging it.
Grinding beats a chisel and a hammer for removing old mortar. It would be worth buying a grinder just to remove mortar if you had a lot of tuckpointing to do. Thicker diamond tuckpointing wheels remove old mortar quickly without disturbing or damaging the bricks. It’s dusty, though, so wear a dust mask and make sure to shut your windows and warn the neighbors.
We’ve only touched on the jobs you can do with an angle grinder. Browse your local hardware store or home center to get a better idea of the angle grinder attachments available. They can save you a ton of time.
Unlike drill motors that run at about 700 to 1,200 rpm, grinders spin at a breakneck speed of 10,000 to 11,000 rpm. They’re fast enough to be scary! Follow these precautions for safe grinder use:
- Wear a face shield and gloves.
- Unplug the grinder when you’re changing wheels.
- Attach the handle and maintain a firm grip with both hands.
- Use the guard if possible.
- Run new wheels for one minute in a protected area before using them to make sure the wheel isn’t defective.
- Orient the work so debris is directed downward.
- Keep bystanders away. Everyone in the vicinity should wear safety glasses.
- Orient the work so the wheel spins away from, not into, sharp edges. Wheels, especially wire wheels, can catch on an edge and throw the workpiece or cause the grinder to kick back (Photo 1).
- Keep sparks away from flammable materials.
- Clamp or secure the workpiece in some fashion.
- Store angle grinders out of children’s reach.
Required Tools for this Project
Have the necessary tools and angle grinder attachments for this DIY project lined up before you start—you’ll save time and frustration.
- Extension cord
- Hearing protection
- Safety glasses
Dry-cut diamond wheel,
Metal cutoff wheel,
Wire cup brush,