A cylindrical steel workpiece of diameter 100 mm is to be turned down to a final diameter of 80 mm. The machine tool can run at a maximum spindle speed of 1500 rpm. The recommended cutting speed for the steel is 120 m min⁻¹. Each turning pass removes a radial depth of cut of 2 mm, and the feed rate is 0.2 mm rev⁻¹. The axial length of the cut is 150 mm. Between successive passes the tool makes a non‑cutting traverse that takes 5 s.

(a) Determine the spindle speed (rpm) that should be used for the first pass.
(b) Calculate the minimum number of passes required to reach the final diameter.
(c) Compute the total machining time for the whole operation (in minutes), including the non‑cutting traverses.

Question

A cylindrical steel workpiece of diameter 100 mm is to be turned down to a final diameter of 80 mm. The machine tool can run at a maximum spindle speed of 1500 rpm. The recommended cutting speed for the steel is 120 m min⁻¹. Each turning pass removes a radial depth of cut of 2 mm, and the feed rate is 0.2 mm rev⁻¹. The axial length of the cut is 150 mm. Between successive passes the tool makes a non‑cutting traverse that takes 5 s.

(a) Determine the spindle speed (rpm) that should be used for the first pass.
(b) Calculate the minimum number of passes required to reach the final diameter.
(c) Compute the total machining time for the whole operation (in minutes), including the non‑cutting traverses.

Accepted Answer

(a) 382 rpm; (b) 5 passes; (c) 10.2 minutes

City Guilds Model Questions Vol1 2020 Engineering Question 30

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