Angle grinder speed is measured in revolutions per minute (rpm). Speeds typically range between 5,000 and 10,000 rpm, though some very robust grinders reach up to 12,000 rpm. Keep in mind, however, that the rpm rating is under “no-load” conditions, meaning that the disc isn’t cutting or grinding anything, just spinning in the air. Other high quality grinders have variable speed to dial in just the right amount of RPM for finishing and polishing operations.
Obviously, the higher the rpm, the easier and more quickly the tool can cut through the target material. Although some discs operate at nominal rpm and remove metal faster, known as fast grind wheels.
Angle grinders measure power output potential in volts (V) and amperes (amps). Cordless angle grinders use volts to measure the power available from their battery, with most cordless models using 18-volt or 20-volt batteries and outliers ranging from 7.5 volts to 24 volts. The “magic number” in most cordless power tools is 18 volts to 20 volts, offering the best mix of affordability and functionality.
Voltage readings on corded angle grinders only indicate whether they can be used with 120-volt or 220-volt power outlets. Shoppers can assess the power output potential of corded models by checking amperage, which ranges from 5 amps to 15 amps. Larger discs will require a larger output, so for a 7- or 9-inch grinder, expect it to have a higher power output potential.
The guard on an angle grinder is a crucial safety measure that covers half the disc. Its purpose is to protect the user’s hands, by preventing sparks and debris from flying toward the user, and to protect surfaces from damage when using the grinder in tight spaces.
Because angle grinders are fast, powerful tools, they can recoil a bit upon power-up. This is particularly true if the grinding wheel is large and heavy. The recoil from the motor can result in the angle grinder jumping in the user’s hands, potentially causing serious injury.
To combat recoil, soft-start technology reduces the power output to the motor at first, slowly increasing until the angle grinder is fully up to speed. This throttled control over the power output prevents an angle grinder from recoiling during start-up, increasing safety while also reducing the jolt to the user’s arms and wrists.
Tips for Buying and Using an Angle Grinder
Keep these tips in mind when choosing and using an angle grinder.
- Always wear personal protective equipment (PPE) including safety glasses/goggles, hearing protection, and respiratory protection when grinding.
- Check the grinder before use to ensure the disc and guard are properly attached and tightened. Discs and guards can become loose between uses. Tighten them before connecting the power to the angle grinder.