METRIC (Coarse and Fine) Chrome Alloy Hand Taps Angle of thread is 60. The crest is flat and the thread has clearance at the root allowing external thread and internal thread to engage well. Larger root radius and lower thread height enable easy screw thread processing and increase thread screw strength. The major diameter of external thread and pitch are specified by a simple numerical value (most commonly measured in millimeters). Bottoming Taps have a lead of two threads and are used to ensure minimum thread run-out when tapping to the bottom of a blind hole. Bottoming Taps are typically preceded by the use of a Taper or Intermediate Tap.