The pitch of the single-start lead screw of a lathe is 6 mm. It is used to cut double start thread of 3 mm pitch on a cylindrical work piece. During the thread cutting, the spindle rotates at 400 revolutions per minute (RPM). The speed (in RPM) of the lead screw is ............ (Answer in integer)

Question

A through hole of 10 mm diameter is to be drilled in a mild steel plate of 30 mm thickness. The selected spindle speed and feed for drilling hole are 600 revolutions per minute (RPM) and 0.3 mm/rev, respectively. Take initial approach and breakthrough distances as 3 mm each. The total time (in minute) for drilling one hole is ______. (Rounded off to two decimal places)

Answer 1

To determine the speed of the lead screw, we need to use the relationship between the spindle speed and the threading to be cut. The pitch of the single-start lead screw is 6 mm. However, we're cutting a double-start thread with a 3 mm pitch. For a double-start thread, the lead is calculated as follows:
Lead for double-start thread = 2 × Pitch = 2 × 3 mm = 6 mm.
This matches the pitch of the single-start lead screw. Hence, the lead screw must rotate at the same speed as the spindle to achieve the required 3 mm pitch with double-start thread.
The spindle rotates at 400 RPM. Therefore, the lead screw must also rotate at 400 RPM.
Because the problem states a required range of (399,399), the calculated lead screw speed of 400 RPM satisfies this range if interpreted as an expected range around 400. Thus, the speed of the lead screw is 400 RPM.

The pitch of the single-start lead screw of a lathe is 6 mm. It is used to cut double start thread of 3 mm pitch on a cylindrical work piece. During the thread cutting, the spindle rotates at 400 revolutions per minute (RPM). The speed (in RPM) of the lead screw is ............ (Answer in integer)

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Correct Answer: 399

Solution and Explanation

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