Quantcast Figure 1-24.Twist drill nomenclature.

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The principal parts of a twist drill are the body, the shank, and the point (fig. 1-24). The dead center of a drill is the sharp edge at the extreme tip end of the drill. It is formed by the intersection of the cone-shaped surfaces of the point and should always be the exact center of the axis of the drill. The point of the drill should not be confused with the dead center. The point is the entire cone-shaped surface at the end of the drill. The lip or cutting edge of a drill is that part of the point that actually cuts away the metal when drilling a hole. It is ordinarily as sharp as the edge of a knife. There is a cutting edge for each flute of the drill. The  shank  is  the  part  of  the  drill  that  fits  into  the socket,  spindle,  or  chuck  of  the  drill  press.  Several types exist (fig. 1-25). The  maintenance  of  twist  drills  and  more  about how to use them on specific jobs are discussed later. REVIEW QUESTIONS Q7. Identify the different types of metal-cutting tools. Q8. What are hawks-bill snips used for? Q9. What are hacksaws used for? Q10. What are taps and dies used for? WRENCHES LEARNING   OBJECTIVES:   Identify   the different types of wrenches. Describe the uses of different types of wrenches. List the safety precautions that apply to wrenches. A  wrench  is  a  basic  tool  that  is  used  to  exert  a twisting force on bolt heads, nuts, studs, and pipes. The special  wrenches  designed  to  do  certain  jobs  are,  in most  cases,  variations  of  the  basic  wrenches  that  are described in this section. The best wrenches are made of chrome vanadium steel.  Wrenches  made  of  this  material  are  lightweight and almost unbreakable. This is an expensive material, however,  so  the  most  common  wrenches  found  in  the Navy are made of forged carbon steel or molybdenum steel.  These  latter  materials  make  good  wrenches,  but they  are  generally  built  a  little  heavier  and  bulkier  to achieve   the   same   degree   of   strength   as   chrome vanadium steel. 1-18 Figure 1-24.—Twist drill nomenclature. Figure 1-25.—Representative shanks.



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