Burr (cutter)

Burrs or burs (sometimes called rotary files)[1][2] are small cutting tools; not to be confused with small pieces of metal formed from cutting metal, used in die grinders, rotary tools, or dental drills.

They share many similarities with endmills and router bits, with the notable distinction that the latter typically have their toolpaths dictated by the machine, while burrs are frequently operated in a freehand manner.

The cutters depicted in the image, being made of tungsten carbide, can withstand and operate at these elevated speeds.

This allows them to function at higher velocities compared to equivalent "HSS" (High-Speed Steel) cutters, all the while retaining the sharpness of their cutting edges.

Hard metal or ceramic workpieces cannot flex beyond the cutting edges, so the tools remove material from them.