Tap with a non-cutting pilot

A method for cutting threads into an interior wall of a bore comprising:

• providing a tap, comprising:
• a torque input head;
• a shaft below the torque input head;
• a cutting zone below the shaft having cutting teeth extending helically along a length of said cutting zone, the cutting teeth defining an inner diameter at a root of the cutting teeth and an outer diameter at a periphery of the cutting teeth;
• a pilot means below the cutting zone for orienting the cutting zone properly in an existing bore, the pilot means defining a guiding zone extending from below the cutting zone to a bottom of the tap, the pilot means having a diameter approximately the same as the inner diameter of the cutting teeth;
• a teeth form relief at a first section of the cutting zone adjacent the pilot means and distal from the shaft;
• at least one area of radial form relief opposite in orientation to the teeth form relief, the radial form relief disposed on the pilot means adjacent the bottom of the tap;
• and
• at least one flute extending from the bottom of the tap and beyond the cutting zone to the shaft;
• and
• inserting the tap into the bore;
• rotating the tap at a speed slow enough to allow the pilot means to align the tap coaxially with the bore;
• rotating the tap further at a speed sufficient for the cutting teeth to form threads on the interior wall of the bore;
• and
• withdrawing the tap from the bore.

A tap for forming threads into an interior bore comprising:

• a cutting zone;
• a pilot means below said cutting zone;
• a first form relief adjacent to a lowest end of said pilot means;
• a second form relief adjacent a lowest part of said cutting zone;
• said second form relief is opposite in orientation to said first form relief;
• and
• a means to cause relative rotation between said tap and the interior bore for forming threads therein.