device for machining contours made of a soft material , such as plastic , and essentially including a rotary tool constituted by abrasive elastic plates whose flexibility makes it possible to dampen the jerks of the member bearing the tool . preferably , a pneumatic motor and a speedometer are used to automatically control the tool at a constant speed guaranteeing a stable machining or cutting force . the method for the automatic machining of flexible burrs on a contour formed of a soft material , is also described .