Frustoconical portions of a blade blank are ground only along their external periphery so that the grounds are cylindrical. The frustoconical portion form openings as well as of 20.degree. to 30.degree. with the generatrix of the cylinder. The blades can be ground a number at a time in the form of a stack with the disk portion. The resulting blades are mounted on the spindles of a ring spinning or ring twisting machine to cut the threads to turn the last thread on spool or bobbin and lower turns on a collecting region of the respective spindle.