A rotary tool is a hand held power tool

Power tool

A power tool is a tool that is actuated by an additional power source and mechanism other than the solely manual labour used with hand tools. The most common types of power tools use electric motors. Internal combustion engines and compressed air are also commonly used...

 with a variety of rotating accessory bits and attachments that can be used for cutting, carving, sanding, polishing and many other applications.

The smaller rotary tools use high RPM

Revolutions per minute

Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...

s to maintain the correct cutting conditions for the tool bits. They have low torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

 which makes them safer for freehand use than the larger higher powered models or similar power tools. A wide variety of accessories are available for applications such as cutting, carving, sanding, polishing

Polishing

Polishing is the process of creating a smooth and shiny surface by rubbing it or using a chemical action, leaving a surface with a significant specular reflection In some materials polishing is also able to reduce diffuse reflection to...

, and grinding

Grinding (abrasive cutting)

Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.A wide variety of machines are used for grinding:* Hand-cranked knife-sharpening stones * Handheld power tools such as angle grinders and die grinders...

. The carving (or cutting) bits are referred to as burrs

Burr (cutter)

Burrs are small cutters used in die grinders, rotary tools or dentist's drills. The name may be considered appropriate when their small sized head is compared to that of a seed of the burr fruit or the teeth compared to a metal burr.To maintain the correct surface speed and cutting conditions...

 and are similar to those used by dentist

Dentist

A dentist, also known as a 'dental surgeon', is a doctor that specializes in the diagnosis, prevention, and treatment of diseases and conditions of the oral cavity. The dentist's supporting team aides in providing oral health services...

s.

Rotary tools are sometimes called "Dremels" because of the market strength of Dremel, a particular brand. But the Dremel name is still protected and is far from legally genericized

Genericized trademark

A genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...

.

Similar tools

A tool similar to a rotary tool but larger and more powerful is a die grinder

Die grinder

A die grinder is a handheld power tool used to grind, sand, hone, polish, or machine material, typically metal but also plastic or wood. They are usually pneumatically driven, although versions with electric and flexible shaft drive also exist...

. Objectively there is little difference, and much overlap of principle and usage, between die grinders, rotary tools, and various surgical and dental drills. All are essentially just a powered spindle

Spindle (tool)

In machine tools, a spindle is a rotating axis of the machine, which often has a shaft at its heart. The shaft itself is called a spindle, but also, in shop-floor practice, the word often is used metonymically to refer to the entire rotary unit, including not only the shaft itself, but its bearings...

 that chucks

Chuck (engineering)

A chuck is a specialized type of clamp used to hold an object, usually an object with radial symmetry, especially a cylindrical object. It is most commonly used to hold a rotating tool or a rotating workpiece...

 cutting tools, usually with a collet

Collet

A collet is a holding device—specifically, a subtype of chuck—that forms a collar around the object to be held and exerts a strong clamping force on the object when it is tightened, usually via a tapered outer collar. It may be used to hold a workpiece or a tool.A collet is a sleeve with a ...

 or quick-change indexable

Indexing (motion)

Indexing in reference to motion is moving into a new position or location quickly and easily but also precisely. After a machine part has been indexed, its location is known to within a few hundredths of a millimeter , or often even to within a few thousandths of a millimeter , despite the fact...

 system, and the power is usually supplied either pneumatically, electrically, or via a flexible shaft

Flexible shaft

A flexible shaft is a device for transmitting rotary motion between two objects which are not fixed relative to one another. It consists of a rotating wire rope or coil which is flexible but has some torsional stiffness. It may or may not have a covering, which also bends but does not rotate...

 drive. The biggest differentiation between these tools is a socially conventional mental categorization by type of user and application: die grinders are mentally categorized as industrial tools; rotary tools are mentally classed as mass-consumer-as-end-user tools (e.g., hobbyists); and medical/surgical/dental tools are mentally classed as medical device

Medical device

A medical device is a product which is used for medical purposes in patients, in diagnosis, therapy or surgery . Whereas medicinal products achieve their principal action by pharmacological, metabolic or immunological means. Medical devices act by other means like physical, mechanical, thermal,...

s.