How To Use an Angle Grinder

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So you’re ready to add an angle grinder to your DIY arsenal. Congratulations — your life is about to get a lot easier! Angle grinders make short work of tough jobs due to their impressive power and speed.  

Once you understand how to keep yourself safe while using one, you’ll be cutting, polishing, and grinding up a storm. 

What Is an Angle Grinder?

An angle grinder is a handheld abrasive power tool. It can be used to grind, cut, polish or sand different materials, including metal, tile, stone, concrete, and wood. It is not possible to use an angle grinder without an attachment, the same way it is not possible to use a drill without a bit.

The attachments are called blades, wheels or discs. 

Angle grinder on a table

How to Use an Angle Grinder

  1. Prepare your workspace. Remove any flammable material from the area. Securely attach the material to be ground, cut, sanded, or polished to your workbench using c-clamps or a vise. 

SAFETY TIP: If working indoors, seal off the room with plastic sheeting. If working outdoors, consider the wind conditions. Close all the windows and doors to the home. Consider warning your neighbors if you’re going to remove mortar, which generates high levels of dust.

  1. If you’re using the angle grinder to cut something, make the appropriate marks on the front and back of the material. Observe where the debris will go and make sure the drop zone is clear. 
  2. Put on appropriate protective gear — old clothes and a leather apron, eye and ear protection, and a full-face shield if you’re going to be using the tool overhead. Gloves are recommended when changing the attachment, but not while operating the tool. 
  3. Select and secure the appropriate attachment for the job you want to perform. To cut through metal, stone, tile or cement, use a cutoff tool. For cleaning jobs, a wire brush is used. A tuckpointing wheel will remove mortar from between bricks. 
  4. Connect the tool to a power source. Angle grinders may be electric or pneumatic (powered by air.)

SAFETY TIP: An electric power tool should always be powered by a GFCI outlet, which will cut off power to the tool in the event of electrical fault.

  1. Put one hand on the main handle and one hand on the auxiliary handle. Both hands should remain on the tool at all times. 
  2. Arrange the blade, disc, or wheel of the tool at the appropriate angle for the job at hand. For cutting and clearing mortar, use a 90 degree angle. To sharpen tools, the wheel should meet the tool at a 20-30 degree angle. For polishing jobs, a 5-10 degree angle is sufficient. No angle is necessary when using a wire brush or wheel. 
  3. Turn the tool on and let it run for one minute without introducing it to any material. This allows the tool to get up to full speed before use, decreasing the risk of injury. 

SAFETY TIP: If there is a defect in the disc or it is improperly attached, there will be a visible wobble as the blade rotates. If you see this, immediately cut power to the tool and unplug it. Try attaching the disc more securely. If it is still wobbly, replace it with a brand new disc. It’s better to delay your project with a trip to the hardware store than a trip to the emergency room. 

  1. Without applying pressure, introduce the attachment of the angle grinder to the material you’re working on. When cutting, this means dropping the blade through the material.  When polishing, sanding, sharpening, or cleaning, this means passing the attachment over the surface of the material at the appropriate angle (as outlined in Step 7.)
  2. Lift the blade, disc or wheel from the surface of the material and turn the power off. Wait until the attachment has completely stopped spinning to set the tool down. Unplug the angle grinder and clean up your workspace. 
Man using an angle grinder

Five Uses for Angle Grinders

The angle grinder is one of the most versatile and useful tools you can add to your tool chest. One of the strongest arguments in favor of purchasing an angle grinder is it’s multifunctionality.  Unlike other tools that only perform one job on one kind of material, angle grinders help you solve all kinds of DIY problems. 

  1. Using an Angle Grinder to Clean Metal

Angle grinders are powerful enough to remove rust, paint, and even hardened concrete from metal tools. Wire wheels are best for getting into cracks and corners. Wire cup brushes are better for broad, flat surfaces. Use caution when cleaning near edges. Make sure the brush is spinning away from the edge, not colliding into it. 

  1. Using an Angle Grinder to Sharpen Tools

Tools that can be sharpened using an angle grinder include; hoes, axes and hatchets, shovels, icepicks and lawn mower blades. As you work watch the metal for signs of overheating or burning. Overheated metal can turn straw-colored, or take on a blue-black tinge. 

  1. Using an Angle Grinder to Cut Metal

For thin materials like sheet metal, use a blade that is 1.0 millimeter or 0.8 millimeters thick. For thicker materials, choose either a 1 millimeter or 1.6 millimeter blade. For heavy steel cuts, use a 1.6 millimeter or 2.5 millimeter thick blade. To cut stainless steel, use an aluminum oxide blade.

Allow the cut to open and the remainder piece to drop freely. This decreases the risk of the blade getting caught. 

  1. Using an Angle Grinder to Cut Tile, Cement, or Stone

When in doubt, opt for a diamond tipped blade wheel. Serrated edge blades work best for natural stone. Blades with notches are used for porcelain tile. A segmented rim blade wheel is designed for cutting concrete. 

Score the front of the material ⅛ of an inch deep. Complete the cut from the back. 

  1. Using an Angle Grinder to Remove Mortar

Removing mortar generates a lot of dust. Consider sealing the area with plastic sheeting. Use a dust mask to protect your lungs. Never use anything but a diamond tip tuckpointing wheel for this job. Keep the edges of the wheel at least ⅛ inch away from brick at all times. 

Angle Grinder Safety Tips

Most DIYers are comfortable using a drill. A high-quality corded drill can rotate 3,000 times in the space of one minute. Angle grinders rotate at more than twice that speed, often with a blade attached. Keeping the tool under your control and taking precautions allows you to use an angle grinder without risking your safety or the safety of your workspace.

How to Prevent Fires

When metal kisses metal at high speeds, sparks fly. Literally. Sparks can cause flammable objects (like your clothing) to ignite.  

To prevent this, direct the shower of sparks away from your clothing and onto a non-flammable surface. Keep the angle grinder moving to avoid accumulation of sparks in one spot. As always, you should have a recently inspected fire extinguisher close to your workbench.

Angle grinder on a table

How to Prevent Physical Injury

Using your angle grinder responsibly will help prevent dangerous accidents. The main causes of physical injury are disc failure, kickback, and debris.  

Physical Injury Due to Disc Failure

Angle grinder discs can and do shatter, usually due to user error. When discs break down, they become projectiles, flung into your workspace at a force of 10,000 RPM. Keep your literal and figurative guards up. 

There are a few reasons why discs might shatter. The first and most common is mismatched RPM between the angle grinder and its accessories.

  • The motor of an angle grinder spins at a certain speed, measured in revolutions per minute, or RPM. 
  • Whatever is attached to the motor will spin at the same speed, but not all accessories are designed for high speeds. 
  • When an accessory is forced to spin at a higher speed than it was designed to tolerate, it is more likely to shatter.

SAFETY TIP: All angle grinder accessories are labeled with the maximum RPM they can safely withstand. Make sure the RPM label on the accessory is equal to or greater than the RPM label on your angle grinder.

Your first line of protection from injury is the angle grinder’s adjustable guard. Never use an angle grinder without a guard. Always adjust the guard before starting to work. Position yourself so that the guard is between the disc and your face. Wear appropriate protective gear as discussed in Step 3. 

A second cause of shattered discs is using an attachment that is past its use-by date. This date can be found on the packaging. Purchase the discs you need on a project-by-project basis rather than stocking up in advance. 

Physical Injury Due to Kick-back 

When used properly, an angle grinder will smoothly cut through tile, concrete, stone, and metal. 

Imperfections in the material or user error can cause the teeth of the blade to ‘catch’, or stop spinning for a moment. 

If power continues to flow to the tool, the angle grinder will start to rotate around the blade, becoming difficult to control. This is called ‘kickback’. Kickback is very dangerous and should be avoided.  

SAFETY TIP: Some angle grinders come equipped with a ‘deadman switch’. When your hand comes off the tool, the switch is released, the electricity cuts off, and the disc will stop spinning.  If you are investing in a new angle grinder, look for one with this feature.

Common Causes of Kickback to Avoid

  • Using a cutting disc for the wrong purpose, such as grinding. Always select a disc or accessory that matches the job at hand. 
  • Grinding, cutting, or polishing near the edge of the material. Use extra caution and a light touch when grinding edges. 
  • Cutting, grinding, or polishing before the disc is spinning at full speed.
  • Operating the angle grinder using only one hand. 

How To Prevent Physical Injury from Debris

An angle grinder is an abrasive removal tool. Whether you’re cutting, grinding, polishing or sanding, debris will be generated. You can decrease the risk of injuries by preparing your workspace appropriately. 

Before you start using the tool, look at the set up of your workbench and material and ask yourself these questions:

Person demonstrating how to use an angle grinder
  • Will the debris generated be solid or particulate? An example of solid debris would be a piece of rebar.  Particulate debris includes dust from cutting stone, cement, or removing mortar, as well as flecks of metal. 
  • Is debris likely to interfere with safe operation of the tool?  The vent of the angle grinder can become clogged with dust, causing the motor to overheat. Check the vent before every use. 
  • Where will the debris go?  If cutting, define a drop-zone and make sure nothing fragile enters it. If generating particulate debris, consider how big the job is and how much dust it will create.  It goes without saying that you never want to inhale particulates. 

Physical Injury from Solid Debris 

To avoid being injured by falling debris, wear closed toed shoes and keep your feet out of the drop-zone. Steel-toed boots offer extra protection from heavy items.  

Physical Injury from Particulate Debris

Inhalation of particulate debris can cause problems ranging from a temporary sore throat to permanent lung damage.  When using an angle grinder, always use a dust-mask to protect your respiratory system. 

When NOT to Use an Angle Grinder (And What to Use Instead)

Should you use an angle grinder to cut wood? While it is possible, it is not recommended. 

Wood offers less resistance to the blade than harder, denser materials. The amount of resistance varies based on the angle of the cut. Less resistance = less control. Less control = increased risk of kickback and injury. 

Instead of an angle grinder, use a jigsaw or circular saw to cut wood. These tools operate at a lower RPM and are better suited to the low resistance of wood. If you must use an angle grinder to cut wood, use a three-tooth saw blade. Fewer teeth = increased resistance. Increased resistance = more control. 

For precision cutting and grinding, use a die grinder. Die grinders can be used with wood, plastic, and metal. Similar to drills, they use bits instead of discs, wheels, or blades.

Choose between a dual-action or random rotation polisher for fine sanding and polishing jobs. 

Conclusion

Angle grinders are more powerful and more dangerous than basic DIY tools such as jigsaws, drills, or electric screwdrivers. The learning curve is steep, and the potential for error and injury looms large. Don’t let this discourage you!

Now that you know how to safely and effectively use an angle grinder, a whole new world of projects is open to you. The flexibility and versatility of this multi-use tool far outweighs its intimidation factor. Stay safe, and happy grinding!

Ellenkate grew up on job sites run by her family’s construction company. She earned her theater degree from The Hartt School, a prestigious performing arts conservatory in Connecticut. Her design and DIY work from her Chicago loft was featured in the Chicago Reader and on Apartment Therapy.