Thread Cutting Operation On Lathe Machine PowerPoint Presentation

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SLIDE-1

THREAD CUTTING OPERATION ON LATHE MACHINE

SLIDE-2

  • INTRODUCTION
  • COMMON OPERATIONS
  • THREAD CUTTING
    • EXTERNAL THREAD CUTTING
    • INTERNAL THREAD CUTTING
  • BORING

SLIDE-3

  • INTRODUCTION
    • A MACHINE TOOL IS A POWER DRIVEN APPARATUS
    • DESIGNED TO PERFORM METAL CUTTING BY VARIOUS TYPES OF CUTTING TOOLS
    • MOSTLY THE MACHINED SURFACES ARE REQUIRED TO BE CYLINDRICAL OR FLAT
    • THE WORK OF MACHINE TOOLS IN GENERAL IS CONCERNED WITH PRODUCING ONE OR BOTH

SLIDE-4

  • INTRODUCTION
    • THE LATHE IS A MACHINE TOOL
    • REMOVES THE METAL FROM A PIECE OF WORK TO GIVE THE REQUIRED SHAPE AND SIZE.
    • BY HOLDING THE WORK SECURELY AND RIGIDLY ON THE MACHINE AND THEN TURNING IT AGAINST CUTTING TOOL
    • REMOVE METAL FROM THE WORK IN THE FORM OF CHIPS

SLIDE-5

  • COMMON OPERATIONS
    • THREAD CUTTING – A THREAD IS A UNIFORM HELICAL GROOVE CUT INSIDE OF A CYLINDRICAL WORKPIECE, OR ON THE OUTSIDE OF A TUBE OR SHAFT
    • BORING – ALSO CALLED INTERNAL TURNING, IS USED TO INCREASE THE INSIDE DIAMETER OF A HOLE. THE ORIGINAL HOLE IS MADE WITH A DRILL, OR IT MAY BE A CORED HOLE IN A CASTING
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SLIDE-6

  • THREAD CUTTING
    • MOST IMPORTANT OPERATIONS
    • PRINCIPLE OF THREAD CUTTING IS TO PRODUCE A HELICAL GROOVE ON A CYLINDRICAL OR CONICAL SURFACE
    • BY FEEDING TOOL LONGITUDINALLY WHEN JOB IS REVOLVED BETWEEN CENTRES OR BY A CHUCK
    • LONGITUDINAL FEED SHOULD BE EQUAL TO THE PITCH OF THE THREAD TO BE CUT PER REVOLUTION OF THE WORKPIECE
    • LEAD SCREW THROUGH SADDLE RECEIVES TRAVERSING MOTION, HAS A DEFINITE PITCH

SLIDE-7

  • EXTERNAL THREAD CUTTING
    • FIRST STEP IS TO REMOVE THE EXCESS MATERIAL FROM THE WORKPIECE TO MAKE ITS DIAMETER EQUAL TO THE MAJOR DIAMETER OF THREAD
    • CHANGE GEARS OF CORRECT SIZE ARE FITTED TO THE END OF THE BED BETWEEN THE SPINDLE AND THE LEAD SCREW
    • SHAPE OR FORM OF THE THREAD DEPENDS ON THE SHAPE OF THE CUTTING TOOL TO BE USED

SLIDE-8

  • EXTERNAL THREAD CUTTING
    • IN A METRIC THREAD, THE INCLUDED ANGLE OF THE CUTTING EDGE SHOULD BE GROUND EXACTLY 60°
    • TOP OF THE TOOL NOSE SHOULD BE SET AT THE CENTRE OF THE WORKPIECE
    • ANGLE GAUGE IS USUALLY USED AGAINST THE TURNED SURFACE
    • SPEED OF THE SPINDLE IS REDUCED BY ONE HALF TO ONE-FOURTH OF THE SPEED REQUIRED FOR TURNING
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SLIDE-9

  • EXTERNAL THREAD CUTTING
    • HALF-NUT IS THEN ENGAGED
    • DEPTH OF CUT, WHICH USUALLY VARIES FROM 0.05 TO 0.2 MM
    • TOOL HAS PRODUCED A HELICAL GROOVE UPTO THE END OF THE WORK, QUICKLY WITHDRAWN BY THE USE OF THE CROSS SLIDE
    • HALF NUT DISENGAGED, AND THE TOOL IS BROUGHT BACK TO THE STARTING POSITION TO GIVE A FRESH CUT

SLIDE-10

  • EXTERNAL THREAD CUTTING
    • BEFORE RE-ENGAGING THE HALF NUT, IT IS NECESSARY TO ENSURE THAT THE TOOL WILL FOLLOW THE SAME PATH IT HAS TRAVERSED IN THE PREVIOUS CUT, OTHERWISE THE JOB WILL BE SPOILED
    • SEVERAL CUTS ARE NECESSARY BEFORE THE FULL DEPTH OF THREAD IS REACHED.

SLIDE-11

  • INTERNAL THREAD CUTTING
    • PRINCIPLE OF CUTTING INTERNAL THREADS IS SIMILAR TO THAT OF AN EXTERNAL THREAD
    • ONLY DIFFERENCE BEING IN THE TOOL USED
    • SIMILAR TO A BORING TOOL WITH CUTTING EDGES GROUND TO THE SHAPE CONFORMING TO THE TYPE OF THREAD TO BE CUT

SLIDE-12

  • INTERNAL THREAD CUTTING
    • HOLE IS FIRST BORED TO THE ROOT DIAMETER OF THE THREAD.
    • TOOL IS FIXED ON THE TOOL POST OR ON THE BORING BAR AFTER SETTING IT AT RIGHT ANGLES TO THE LATHE AXIS, USING A THREAD GAUGE/ANGLE GAUGE.
    • DEPTH OF CUT IS GIVEN BY THE COMPOUND SLIDE AND THE THREAD IS FINISHED IN THE USUAL
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SLIDE-13

  • BORING
    • OPERATION OF ENLARGING AND TRUING A HOLE PRODUCED BY DRILLING, PUNCHING, CASTING OR FORGING
    • CAN’T ORIGINATE A HOLE
    • SIMILAR TO THE EXTERNAL TURNING OPERATION
    • CAN BE PERFORMED IN A LATHE

SLIDE-14

  • COUNTER BORING
    • OPERATION OF ENLARGING A HOLE THROUGH A CERTAIN DISTANCE FROM ONE END INSTEAD OF ENLARGING THE WHOLE DRILLED SURFACE
    • SIMILAR TO A SHOULDER TURNING OPERATION IN EXTERNAL TURNING

SLIDE-15

  • TAPER BORING
    • THE PRINCIPLE OF TURNING A TAPER HOLE IS SIMILAR TO THE EXTERNAL TAPER TURNING OPERATION
    • ACCOMPLISHED BY ROTATING THE WORK ON A CHUCK AND FEEDING THE TOOL AT AN ANGLE TO THE AXIS OF ROTATION OF THE WORK PIECE

SLIDE-16

  • THANK YOU

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