How to Use an Angle Grinder

We got our Pro team together to give you some tips on how to use an angle grinder from basics to some advanced techniques and shortcuts. Angle grinders are controlled by either a trigger, paddle, or switch. They spin a disc at an incredible rate of speed for the express purpose of sanding, grinding, or cutting.

Due to the rapid advancements in lithium-ion battery technology, the many angle grinder uses have expanded dramatically. This makes it a versatile tool used by a wide range of professionals. With so much flexibility at your disposal, the angle grinder also has a steep learning curve compared to many other tools.

Before you use an angle grinder, you’ll want to grab some personal protection gear. The reality of the angle grinder is that it’s a loud tool that kicks a whole lot of debris around. Plus, you’re not always grinding or polishing. Oftentimes, the job entails cutting. If you get sloppy with a cutting wheel or simply have bad luck, that wheel could turn into high-speed shrapnel.

For these reasons, you’ll do yourself a favor if you grab some hearing protection, long sleeves, gloves, and something to shield your entire face. You don’t want to take a hot shard of cut-off wheel to the moneymaker, after all. A grinder can also ruin your clothing, so wear protective outerwear if you don’t want pinholes in your clothes from flying hot metal.

Pro Tip: Having a cutting wheel fly apart on you at 10,000 RPM is no joke. There’s nothing you can do when it happens. As a result, you want to always wear a full face shield when using a cutting wheel—even when using a guard. Grinding and using a flap disc doesn’t typically present the same level of danger, so the guard and adequate eye protection are often enough.

We recommend doing what’s known as a “ring test” on any grinding wheel before affixing it to your grinder. You can actually do this on bench grinders as well. You basically suspend the grinder wheel from a pencil or other project. Then, gently tap it with the handle of a screwdriver or similar tool—anything not made of metal. Rotate it 180 degrees and do it again. A wheel in good condition should let out a distinctive metallic “ringing” sound.

That metallic ring comes indicates the integrity of the grinder wheel. An internally- or externally-cracked wheel typically stops the vibrations at the damaged point—preventing a clear ring. While the ring test does a good job of giving you an idea of the integrity of the wheel, you also want to follow up with a quick visual inspection.

Once you’re reasonably certain of the integrity of your grinding wheel, go ahead and mount it. The last thing we recommend before starting is to run that wheel on its own (pointed away from your face) for 15-30 seconds. This helps you know (by feel) if it’s properly centered and mounted and if there are any issues with the wheel balance.

Because angle grinders quickly remove lots of material, lower the risk as much as possible by positioning the tool properly. Using an angle grinder in different applications and with certain attachments calls for different angles. Ensuring sparks and debris fly away from your body reduces your chances of getting injured. Your work clothes will last longer, too!

For surface grinding, use the flat part of the wheel, maintaining a 20°-30° angle between the tool and the work surface. Position the blade guard at the back toward your body. Use a smooth back-and-forth motion to guide the flap disc over the material. Let the wheel do the work, but feel free to apply enough pressure to ensure you’re being productive.

You can really grind down welds quickly in preparation for painting using this method.

You should tackle cutting straight on since you want to use the edge of your wheel to cut into the work surface. Be careful not to bend the cutting wheel in any direction. In this mode, the guard always goes on top to protect you from debris. Wearing a face shield also protects you against premature disc failure. And remember—if the guard isn’t between the cutting disc and your face—move it until it is.

Also—and this might go without saying—never “plunge cut” a cutting wheel into the material. Cutting at the 12 o’clock position is a recipe for kickback and loss of control. Instead, cut downward as shown in the image above.

Kickback occurs any time the grinder wheel stops suddenly. This forces the grinder in the opposite direction of the rotation at the point of pinching. Knowing how to use an angle grinder in a way that avoids this can keep you safe. For cut-off applications, this can happen when the waste piece sags under its own weight—suddenly pinching the blade and causing the tool to transfer all that rotational energy into a kickback event.

Guard against this by properly using blade guards and by supporting your material properly so it doesn’t sag when making an abrasive cut.

You can also experience kickback when using abrasive wheels to grind down material. Corners, sharp edges, and other areas present possible points of kickback that can damage and/or stop a wheel suddenly. Take care to use the auxiliary handle in a way that gives you leverage to protect yourself should this occur. Never EVER use a grinder with one hand!

For sanding applications, hold the tool at a 5°-10° angle to the work surface. For pretty much all grinder applications, apply only minimum pressure. You want to let the tool and the abrasive accessory do the hard work.

Check the manufacturer’s specs when attaching your wheel, disc, or cup. The max RPM on the accessory should meet or exceed the max RPM of the grinder you plan to use. If the rated speed of the accessory is lower than your grinder, you run the risk of the wheel flying apart.

I don’t care if a company offers circular saw-style blades that fit your grinder. These tools operate at a significantly higher RPM than any handheld circular saw. You NEVER want to use toothed blades on a grinder. That includes those “wood carving chain discs” that use chainsaw teeth as well as anything with carbide-toothed blades. Just don’t do it.

If you’ve got any additional tips or tricks on how to use an angle grinder, feel free to leave a comment below.

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