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Chapter 38 Taps and Dies
Types and Uses - Continued - 14256_231

Tools And Their Uses - Hand tools and what they are used for
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TM 9-243 TYPES AND USES Taps  and  dies  are  used  to  cut  threads  in  metal,  plastics or hard rubber. The taps are used for cutting internal threads, and the dies are used to cut external threads. TAPS Taps  are  made  of  hardened  steel  and  have  the  following parts:  a  square  end  (1)  a  round  shank  (2)  a  body (threaded) section (3) and a chamfer (4). The square end is used to turn the tap with either a straight or T-handled  tap  wrench.  The  shank  is  a  smooth,  rounded section which is immediately behind the threaded sec- tion. The body (threaded) section contains four flutes which  have  threads  cut  into  their  upper  edges.  They have a hollow section near the center to permit metal shavings to fall away from the cutting edges. The chamfer is the non-threaded end of the tap. It allows the tap to be positioned squarely in the metal to be threaded without engaging the threads of the tap. TAPER  (STARTING)  HAND  TAP The taper (starting) hand tap has a chamfer (non- threaded)  length  equal  to  eight  to  ten  threads.  The  taper hand tap is used to start tapping operations. BOTTOMING  HAND  TAP The bottoming hand tap has a chamfer length equal to one to one and one-half threads. This tap is used for threading  the  bottom  of  a  blind  hole  only  after  the  taper and plug taps have been used. This tap is also used when tapping hard materials. PLUG/PIPE  HAND  TAP The  pipe  tap  has  a  tapered  diameterwhich  increases  at a rate of 3/4 inch per foot. All the threads on the pipe tap are designed to cut pipe. The pipe tap is used for cutting pipe fittings and in other places where extremely tight fits are required. BOILER  HAND  TAPS There  are  two  types  of  boiler  taps,  straight  and  tapered. Straight boiler taps range in size from 1/2 inch to 1-1/2 inches in diameter and have a chamfer for starting the tap. Tapered boiler taps have tapered diameters which increase at a rate of 3/4 inch per foot. 38-2 Change   1







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