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Boring
Summary - 14076_180

Engineman 2 - Intermediate engine mechanics training manual
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Figure  9-30.–Boring bars. Figure  9-31.–Tapers. of  large  diameter.  The  head  is  fitted  with  a  fly  cutter similar to the one shown in view A of figure 9-30. The setscrew with the tapered point adjusts the cutter to the work TAPERS Although  you  will  probably  have  little  need  to machine   tapers,   we   have   provided   the   following explanation for your basic knowledge. A taper is the gradual decrease in the diameter of a piece of work toward one end. The amount of taper in any given length of work is found by subtracting the size of the small end from the size of the large end. Taper is usually  expressed  as  the  amount  of  taper  per  foot  of length  or  taper  per  inch  of  length.  We  will  take  two examples. (See fig. 9-31.) Example  l.–Find  the  taper  per  foot  of  a  piece  of work 2 inches long. The diameter of the small end is 1 inch; the diameter of the large end is 2 inches. The amount of taper is 2 inches minus 1 inch, which equals 1 inch. The length of the taper is given as 2 inches. Therefore, the taper is 1 inch in 2 inches of length. In 12 inches of length the taper is 6 inches. (See fig. 9-31.) Example  2.–Find  the  taper  per  foot  of  a  piece  6 inches long. The diameter of the small end is 1 inch; the diameter of the large end is 2 inches. The amount of taper is the same as in example 1, that is, 1 inch. However, the length of this taper is 6 inches; hence the taper per foot is 1 inch times 12/6, which equals 2 inches per foot (fig. 9-31). SAFETY  PRECAUTIONS In  machining  operations,  always  keep  safety  in mind,  no  matter  how  important  the  job  is  or  how well  you  know  the  machine  you  are  operating. Listed  here  are  some  safety  precautions  that  you MUST  follow: 1.  Before  starting  any  lathe  operations,  always prepare  yourself  by  rolling  up  your  shirt  sleeves  and removing  your  watch,  rings,  and  other  jewelry  that might become caught while you operate the machine. 2. Wear goggles or an approved face shield at all times whenever you operate a lathe or when you are near a lathe that is being operated. 3.   Be sure the work area is clear of obstructions that you might fall or trip over. 4. Keep the deck area around your machine clear of oil or grease to prevent the possibility of slipping or falling  into  the  machine. 5.   Always   use   assistance   when   handling   large workpieces or large chucks. 6.  NEVER  remove  chips  with  your  bare  hands. Use a stick or brush, and always stop the machine. 7.   Always secure power to the machine when you take measurements or make adjustments to the chuck. 8. Be attentive, not only to the operation of your machine, but also to events going on around it. NEVER permit skylarking in the area. 9.   Should it become necessary to operate the lathe while  the  ship  is  underway,  be  especially  safety conscious.  (Machines  should  be  operated  ONLY  in relatively calm seas.) 9-19







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