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Railways NTPC (Technical Ability) Metal Forming, Casting and Cutting Question Bank Metal Cutting

  • question_answer
      A single short thread of pitch 2 mm is to be produced on a lathe having a lead screw with a double start thread of pitch 4 mm. The ratio of speeds between the spindle and lead screw for this operation is:

    A) 1 : 2                             

    B) 2 : 1

    C) 1 : 4                             

    D) 4 : 1

    Correct Answer: C

    Solution :

    \[\frac{Spindle\,\,of\,\,fset}{Lead\,\,screw\,\,speed}\] \[\frac{pitch\,\,of\,\,threads\,\,to\,\,be\,\,produceed}{Number\,\,of\,\,starts\times Pitch\,\,of\,\,threads\,\,of\,lead\,\,screw}\]\[=\frac{2}{2\times 4}=\frac{1}{4}\,\,or\,\,1:4\]


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