Working process of the GN-Gratex® I for taps

fig. 1 fig. 2 fig. 3 fig. 4
  • The right-hand cutting tap works as usual (see fig. 1).
  • When tapping has been finished, the spring of the GN-Gratex® I is tightened (fig. 2).
  • When turning back, the left-hand cutting GN-Gratex I deburs the tap hole at the same time (fig. 3).
  • After finishing the tap hole, it is already deburred or chamfered (fig. 4).

Set-up the tap depth

  • The teeth of GN-Gratex I-cutting head (E) has to be located at the surface of the work piece.
  • The screw (B) of the fixating ring (A) is loose.
  • The drilling spindle is lowered until the desired cutting depth is reached.
  • The fixating ring (A) of the GN-Gratex I is now pushed down to create the required pressure for the chamfering. The required pressure has to be adapted to the machined material and the size of the bur. The compression of the spring (C) should not exceed 80%. Some taps might have flutes that are too short for the required travel length of the GN Gratex I-cutting head. In this case, the flutes of the tap can be lengthened using a suitable grinding disc with rubber compound.

Mounting the GN-Gratex® I

In the case of taps with thicker shanks, the GN-Gratex I is mounted from the top edge of the tap starting with the fixating ring (A). It is fixed at the desired position by tightening the screw (B) on the fixating ring. For taps with thin shanks, the fixating ring (A) and the spring (C) of the GN-Gratex I are mounted from the shank's end starting with the spring. The cutting head (D) is mounted from the cutting end of the tap and fixed with its latch to the spring (C).


The GN-Gratex I cutting head should be free to move along the whole flute length, otherwise a special adaptation is required. Taps, whose flutes narrow towards the shank, need to be reground to avoid the breakage of teeth. All GN-Gratex I are suited to common machine taps with normal straight or slightly helical (max. 15°) flutes.