A radial, grinder or angle grinder, angle grinder, flexible, biscuit cutter, reglette, burr or rotaflex is a tool used for cutting, grinding and polishing.

An angle grinder can be driven by a motor, which drives a gear head at a right angle on which is mounted a grinding wheel or a thinner cutting wheel which can be replaced when they wear out. Angle grinders typically have an adjustable guard for operation with either hand. Certain angle grinders, depending on their speed range, can be used as sanders using a sanding disc with a backing pad. The protective system is usually made of a hard plastic, phenolic resin or medium hard rubber depending on the amount of flexibility desired.

Angle grinders can be used both to remove excess material from pieces and to cut them into pieces. There are many different types of discs used for various types of materials and jobs: cutting discs (diamond blade), abrasive grinding discs, grinding stones (grinding stones), sanding discs, wire brush wheels, and polishing pads. The angle grinder has large ball bearings (ball bearings or bearings) to counteract the lateral forces generated during cuts. In this it differs from the drill, where the force is axial.

Angle grinders are widely used for metalworking and construction work, as well as in emergency rescue. We commonly find them in workshops, auto body repair shops, bodywork.[1]​.

There are a wide variety of angle grinders to choose from when it comes to finding the right one for the job. Disc size and motor power are the most important factors when choosing the right angle grinder.

Another factor is the driving power (pneumatic or electric), the rpm (revolutions per minute) and the arbor size. Usually the disk size and drive power increase together. Disc size is usually measured in inches or millimeters. Common disc sizes for angle grinders in the United States include 4, 4.5, 5, 6, 7, 9, and 12 inches. In Europe they range from 115 mm, 125 mm to 230 mm, there are also battery-powered grinders, which provides more comfort in hard-to-reach places. Discs for pneumatic grinders are also available much smaller. Pneumatic grinders are used for lighter jobs where more precision is required. This is because pneumatic grinders can be small and lightweight but remain powerful because they do not contain a heavy copper-wound motor, while it is harder for an angle grinder to maintain proper momentum if it were smaller. Electric angle grinders are commonly used more for heavier and larger jobs. However, there are also electric angle grinders and larger pneumatic angle grinders.