Method and tool for producing a threaded hole

A method for producing a threaded hole in a workpiece with a thread tapping tool bit, which has a main cutting edge at its drill bit tip and a thread profile that trails in a thread tapping direction with at least one thread cutting tooth, comprising:

• in a thread tapping stroke, the main cutting edge produces a core hole, and, at the same time, the thread profile forms an internal thread at the inner wall of the core hole until a target thread depth is reached, and, is conducted with a thread tapping advance in the thread tapping direction and at a thread tapping rotational speed of the thread tapping tool bit synchronized with it, wherein, after the thread tapping stroke, an oppositely directed reversing stroke is produced, in which the thread tapping tool bit is withdrawn out from the threaded hole in a reversing direction, and, is conducted with an opposite reversing advance, wherein the thread profile has at least one broaching cutting edge, and when the reversing stroke is carried out, a broached groove is produced by the broaching cutting edge, through which the thread cutting tooth is withdrawn out from the threaded hole in a load-free manner, without removal of material, in that, between the thread tapping stroke and the reversing stroke, a groove-forming step is produced, in which the thread tapping stroke is prolonged in the thread tapping direction by a groove-forming stroke, and, this is conducted for forming a peripheral groove without thread pitch that adjoins the internal thread, in which the thread profile can rotate without advance in a load-free manner, and, in the groove-forming step, the thread tapping drill bit is moved in the thread tapping direction beyond the target thread depth until it reaches a target hole depth, and, is moved with a groove-forming advance and at a groove-forming rotational speed that are not synchronized with each other, and/or are different from the thread tapping advance and from the thread tapping rotational speed.

A thread tapping tool bit for carrying out a method for producing a threaded hole in a workpiece, comprising:

• a clamping shaft and thread tapping body that is adjoined thereto, and along the longitudinal axis of which at least one chip groove extends up to a front-end main cutting edge at the drill bit tip, at which main cutting edge, a chip surface delimiting the chip groove and a front-end free surface of the drill bit tip converge, wherein, in the peripheral direction of the tool bit, the chip groove is delimited by at least one drill bit web, and the chip surface of the chip groove transitions, with the formation of an auxiliary cutting edge, into a back surface of the drill bit web on the outer peripheral side, and wherein the auxiliary cutting edge and the front-end main cutting edge converge at a radially outer main cutting edge, wherein, at the back surface of the drill bit web on the outer peripheral side, a thread profile with at least one thread-profile cutting tooth is formed, wherein the thread-profile cutting tooth has a radial outer profile-base cutting edge, which protrudes radially outward over the main cutting edge by a cutting tooth height, and wherein the radial outer profile-base cutting edge extends along the longitudinal axis of the drill bit, wherein the thread profile has at least one broaching cutting edge, and, when the reversing stroke is carried out, a broached groove can be produced by the broaching cutting edge, through which the thread cutting tooth can be withdrawn out from the threaded hole in a load-free manner, in that the thread-profile broaching cutting edge has a radially outer groove-bottom cutting edge, which protrudes radially outward over the main cutting edge by a broaching cutting edge height, and the groove-bottom cutting edge transitions into lateral groove-flank cutting edges, and the groove-bottom cutting edge extends in the peripheral direction of the drill bit and is aligned at a right angle to the profile-base cutting edge of the thread-profile cutting tooth.