Abstract: The tapping drill having a drive shaft driven with an alternating rotational movement, comprises, disposed between this drive shaft and the tool carrier, a ratchet mechanism capable, at will, of transforming the alternating rotational motion into a rotating movement by successive impulses in one direction or the other. The ratchet mechanism comprises a dog with spring extending through an annular member integral with the tool carrier, this dog bearing in an axial groove formed in an interior member integral with the drive shaft, in which interior member there can successively be distinguished three parts:a first part comprising solely the groove;a second part in which the groove is flanked by a cut-away on one side,a third part in which the groove is flanked by a cut-away on the other side,the dog being able to slide freely into the cut-aways and to be displaced along the groove. The dog is displaced along the groove by a control member bearing with play in an annular groove formed in the annular member.

Abstract: A process and apparatus for drilling holes in hard materials in surgical procedures, comprising driving a drilling tool with a movement of alternating rotation with an amplitude of less than one revolution. The tool can be driven from a motor having unidirectional continuous rotatable movement through a convertor which transforms this movement into the alternating rotation. The drilling tool can covered by a member which feeds the waste cutting materials rearwardly into an enclosed chamber. The apparatus can also be provided with a member that covers the drill during an insertion thereof through cut tissue prior to the drilling operation.