Question

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 speed of the lead screw is:

• A. 200 rpm
• B. 20 rpm
• C. 120 rpm
• D. 180 rpm

Hint:

To calculate lead screw speed, use the formula: Lead screw speed = (Spindle speed × Pitch of lead screw) / Pitch of thread.

Answer 1

The Correct Option is B

1. Relation Between Spindle Speed and Lead Screw Speed:
The speed of the lead screw (or the feed rate) is determined by the spindle speed and the pitch of the lead screw. The relationship is: \[ \text{Lead screw speed} = \frac{\text{Spindle speed} \times \text{Pitch of lead screw}}{\text{Pitch of thread to be cut}} \] 2. Substituting Values: \[ \text{Lead screw speed} = \frac{60 \, \text{rpm} \times 6 \, \text{mm}}{2 \, \text{mm}} = 20 \, \text{rpm} \] 3. Conclusion:
The speed of the lead screw is 20 rpm to cut the screw threads with a 2 mm pitch.