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Chapter 9 Lathes and Lathe Machining Operations
Carriage

Engineman 2 - Intermediate engine mechanics training manual
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turning, boring, facing, and thread cutting. But it may also be used for drilling, reaming, knurling, grinding, spinning, and spring winding. Since you will primarily be  concerned  with  turning,  boring,  facing,  and  thread cutting, we will deal primarily with those operations in this chapter. The work held in the engine lathe can be revolved at  any  one  of  a  number  of  different  speeds,  and  the cutting  tool  can  be  accurately  controlled  by  hand  or power   for   longitudinal   feed   and   crossfeed. (Longitudinal feed is the movement of the cutting tool parallel  to  the  axis  of  the  lathe;  crossfeed  is  the movement of the cutting tool perpendicular to the axis of the lathe.) Lathe size is determined by two measurements: (1) the diameter of work it will swing (turn) over the ways and (2) the length of the bed. For example, a 14-inch by 6-foot lathe will swing work up to 14 inches in diameter and has a bed that is 6 feet long. Engine lathes vary in size from small bench lathes that have a swing of 9 inches to very large lathes for turning   large   diameter   work   such   as   low-pressure turbine rotors. The 16-inch lathe is the average size for general purposes and is the size usually installed in ships that have only one lathe. PRINCIPAL  PARTS To  learn  the  operation  of  the  lathe,  you  must  be familiar with the names and functions of the principal parts.   Lathes   from   different   manufacturers   differ somewhat in construction, but all are built to perform the same general functions. As you read the description of each part, find its location on the lathe in figure 9-1 and  the  figures  that  follow.  (For  specific  details  of features of construction and operating techniques, refer to   the   manufacturer’s   technical   manual   for   your machine.) Bed and Ways The bed is the base or foundation of the parts of the lathe. The main feature of the bed is the ways, which are formed on the bed’s upper surface and run the full length of the bed. The ways keep the tailstock and the carriage, which slide on them, in alignment with the headstock. Headstock The headstock contains the headstock spindle and the  mechanism  for  driving  it.  In  the  belt-driven  type, shown in figure 9-2, the driving mechanism consists of Figure 9-2.—Belt-driven type of headstock. a  motor-driven  cone  pulley  that  drives  the  spindle  cone pulley through a drive belt. The spindle can be rotated either directly or through back gears. When  the  headstock  is  set  up  for  direct  drive,  a bull-gear pin, located under a cover to the right of the spindle pulley, connects the pulley to the spindle. This connection causes the spindle to turn at the same speed as the spindle pulley. When  the  headstock  is  set  up  for  gear  drive,  the bull-gear  pin  is  pulled  out,  disconnecting  the  spindle pulley from the spindle. This allows the spindle to turn freely inside the spindle pulley. The back-gear lever, on the left end of the headstock, is moved to engage the back-gear set with a gear on the end of the spindle and a  gear  on  the  end  of  the  spindle  pulley.  In  this  drive mode, the drive belt turns the spindle pulley, which turns the back-gear set, which turns the spindle. Each drive mode provides four spindle speeds, for a  total  of  eight.  The  back-gear  drive  speeds  are  less slower than the direct-drive speeds. Tailstock The primary purpose of the tailstock is to hold the dead  center  to  support  one  end  of  the  work  being 9-2







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