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

  • question_answer
    It is required to cut screw threads of 2 mm pitch on a lathe. The lead screw has a pitch of 6 mm.If the spindle speed is 60 rpm, then the speed of the lead screw will be:

    A) 10 rpm             

    B) 20 rpm

    C) 120 rmp                       

    D) 180 rpm

    Correct Answer: B

    Solution :

    \[\frac{Speed\,\,of\,\,lead\,\,screw}{Speed\,\,of\,\,spindle}=\frac{Pitch\,\,of\,\,threads}{pitch\,\,of\,\,lead\,\,screw}\] Speed of lead screw \[=\left( \frac{2\times 60}{6} \right)=20\,rmp\]


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