Question

Centre lathe is to be used to cut inch thread of 4 threads per inch lead screw of lathe has 3 mm pitch. Then change gear to be used is
1. \(\frac{1}{12}\)
2. \(\frac{127}{60}\)
3. \(\frac{30}{127}\)
4. \(\frac{20}{80}\)

Answer 1

Correct Answer - Option 2 : \(\frac{127}{60}\)

Concept:

Gear ratio= (pitch in mm/ pitch of lead screw of lathe)

1 inch = 25.4 mm

Calculation:

Pitch in mm = 25.4/4 = 6.35

∴ Gear ratio= 6.35/3= 2.1166 i.e. 127/60