Angle grinders—handheld tools used to cut, sharpen, shape, and polish everything from stone and brick to steel and iron—are useful in many situations and found in many work environments. Infinitely versatile, they are especially common at auto garages and fabrication shops, but they are also utilized around the house for DIY projects.
While there are many different types of grinders available, including wet grinders that use water to cool its cutting wheel, and heavy-duty bench grinders that are stationary and attached to a work table, angle grinders are the most popular.
They’re called angle grinders because they are built with a right-angled gearhead that features an attached disc. This disc is what is swapped out and replaced with other specific abrasive discs based on the job at hand. Different disc attachments are used to do things such as cut a piece of kitchen tile, polish a slab of marble, or any number of tasks. Other attachments include wire brush wheels, which are useful for cleaning caked-on dirt from tools and equipment. The number of uses and corresponding attachments is almost endless.
Size Matters
Before purchasing an angle grinder, you first need to determine the disc size needed. Here’s a quick look at the two size categories:
- Small angle grinders feature discs 7" or smaller
- Large angle grinders have discs 7" or larger
Both can be electric or cordless, but all angle grinders are handheld. This mobility makes them ideal for large projects that could not be reached with a stationary machine.
If you plan to work on wider surfaces, the large angle grinder is typically the best choice, as it will deliver deeper cuts and make the work go quicker than if you used a grinder with small discs. Jobs requiring more precision, like polishing detailed metal or stone, call for a small angle model.
Speed Needs
The speed of an angle grinder is measured in what’s known as “no-load speed.” This refers to how fast the disc rotates before making contact with whatever material it is working on. The range is typically between 5,000 to 11,000 RPM. Higher RPMs equal a more precise cut and a more pronounced grinding action versus lower RPMs. However, slower speeds produce less heat and make less noise, so choose what works best for you.
Some angle grinders feature variable speed motors that provide more control by allowing you to adjust the speed of the disc. This makes the tool even more versatile, as you can switch from slow speeds on polishing jobs to higher speeds when cutting or sanding.
Attachments and Features
Look for grinders that feature vacuum attachments or another form of dust protection—this not only keeps the machine’s internal parts free from dirt and other particles, it also sucks up the inevitable dust build-up around your work area.
Movable side handles allow the tool to be used with both the right and left hands, while anti-vibration handles can bring added control and also help with fatigue when using your grinder for multiple hours at a time. Another handy feature is the lock-on switch, which lets the user keep the grinder running without repetitively pressing the switch on and off.
Safety First
Because the discs on even the lowest RPM models spin extremely fast, which creates sparks and sprays stray metal particles, most experts advise choosing an angle grinder that comes equipped with a safety guard. These covers not only protect the operator from injury, they also help prevent potential fire hazards in garages and other workplaces.
Another valuable safety feature is the anti-kickback clutch, which cuts the motor of the grinder if the spinning disc gets caught in a piece of metal or other material, stopping the machine from jerking back toward the operator when in use.
Tips for Using an Angle Grinder
While certain features can help enhance the safety of these powerful machines, always wear protective gear when operating them. That means long sleeves, work gloves, a plastic face shield, and hearing protection.
Be careful how you position the grinder when in use. Make sure to match the angle to the task at hand.
For example, simple surface grinding calls for the flat part of the wheel to sit at a 20° to 30° angle. Steady back and forth movements will do the trick. Apply a little pressure, but let the machine do the heavy lifting. The blade guard should be in the back, towards the body.
If you’re making a cut into metal or steel, you need to use the straight edge of the wheel. Make sure the blade guard is on top to protect your face and body from sparks and particles. Don’t turn the wheel in any direction other than straight down to make your cut.
When sanding or polishing, you usually want to hold the grinder at between 5° and 10° and apply the least amount of pressure possible to get the job done. Keep the tool moving at all times and you’ll minimize the chance of digging into the surface of your work material.
Finally, when you’re done using your grinder, always make sure the discs come to a complete stop before putting the machine down. Remember, even if the blade is spinning slowly, it can do serious damage to you or those around you.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.