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Thread Dial Indicator
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Engineman 2 - Intermediate engine mechanics training manual
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Figure 9-17.—Micrometer carriage stop. the lead screw. On the upper end of the shaft is the dial. As the lead screw revolves, the dial is turned and the graduations  on  the  dial  indicate  points  at  which  the half-nuts may be engaged. Carriage    Stop The carriage stop can be attached to the bed at any point where the carriage should stop. It is used primarily for  turning,  facing,  or  boring  duplicate  parts,  as  it eliminates  taking  repeated  measurements  of  the  same dimension. In operation, the stop is set at the point where the  feed  should  stop.  To  use  the  stop,  just  before  the carriage   reaches   the   stopping   point,   shut   off   the automatic feed and manually run the carriage up against the  stop.  Carriage  stops  are  provided  with  or  without micrometer   adjustment.   Figure   9-17   shows   a micrometer carriage stop. Clamp it on the ways in the approximate position required, and then adjust it to the exact setting by using the micrometer adjustment. (Do not confuse this stop with the automatic carriage stop that  automatically  stops  the  carriage  by  disengaging  the feed  or  stopping  the  lathe.) MAINTENANCE Every lathe must be maintained strictly according to  requirements  of  the  Maintenance  and  Material Management (3-M) Systems. The first requirement of maintenance  to  your  lathe  is  proper  lubrication.  Make  it a  point  to  oil  your  lathe  daily  where  oil  holes  are provided. Oil the ways daily-not only for lubrication but to protect their scraped surfaces. Oil the lead screw often while  it  is  in  use;  this  is  necessary  to  preserve  its accuracy, for a worn lead screw lacks precision in thread cutting. Make sure the headstock is filled to the proper oil level; drain the oil out and replace it when it becomes dirty  or  gummy.  If  your  lathe  is  equipped  with  an automatic oiling system for some parts, make sure all those parts are getting oil. Make it a habit to CHECK frequently  to  see  that  all  moving  parts  are  being lubricated. Before engaging the longitudinal ‘feed, be certain that  the  carriage  clamp  screw  is  loose  and  that  the carriage  can  be  moved  by  hand.  Avoid  running  the carriage  against  the  headstock  or  tailstock  while  it  is under the power feed; running the carriage against the headstock  or  tailstock  puts  an  unnecessary  strain  on  the lathe and may jam the gears. Do not neglect the motor just because it may be out of sight; check its lubrication. If it does not run properly, notify  the  Electrician’s  Mate  who  is  responsible  for caring for it. He or she will cooperate with you to keep it in good condition. On lathes with a belt driven from the motor, avoid getting oil or grease on the belt when you oil the lathe or motor. Keep your lathe clean. A clean and orderly machine is an indication of a good mechanic. Dirt and chips on the ways, on the lead screw, and on the crossfeed screws will cause serious wear and impair the accuracy of the machine. NEVER put wrenches, files, or other tools on the ways. If you must keep tools on the bed, use a board to protect the finished surfaces of the ways. NEVER  use  the  bed  or  carriage  as  an  anvil. Remember, the lathe is a precision machine, and nothing must  be  allowed  to  destroy  its  accuracy. BASIC SETUP A knowledge of the basic setup is required if you are to become proficient in performing machine work with a lathe. Some of these setups are considered in the following  sections. Cutting Speeds and Feeds Cutting speed is the rate at which the surface of the work passes the point of the cutting tool. It is expressed in feet per minute (fpm). Feed  is  the  amount  the  tool  advances  for  each revolution   of   the   work.   It   is   usually   expressed   in thousandths  of  an  inch  per  revolution  of  the  spindle. Cutting  speeds  and  tool  feeds  are  determined  by various considerations: the hardness and toughness of 9-10







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