HHS Steels with good machinability
    Rm < 750 N/mm² (101,500 PSI)
    Nodular graphite, Malleable cast iron
    Long chip brass, Cast aluminium alloys
       Si > 10% ( short-chipping )

   Handtap No. 1 of a serial tap set consists
   of 3 or 2 taps.
   This tap cannot finish the thread because

   it is serial form, (major & pitch diameters
   below the basic thread dimensions).
   4 thread chamfer lead.
   Rake angle 8° - 10°.

   Handtap No. 2 of a serial tap set consists
   of 3 taps.
   This tap cannot finish the thread because

   it is serial form, (major & pitch diameters
   below the basic thread dimensions).
   3 thread chamfer lead.
   Rake angle 8° - 10°.

   Handtap No. 3 of a serial tap set consists
   of 3 or 2 taps.
   This tap finishes the thread to the
   required tolerance.

   2 thread chamfer lead (DIN-Form C).    Rake angle 8° - 10°.

   Handtap set consisting of 3 or 2 taps:

   101 = 101/1 + 101/2 + 101/3
   for M - UNC - W threads.

   101 = 101/1 + 101/3
   for MF - UNF - BSF - G threads.