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)

Hint:

When calculating drilling time, consider both the feed rate and the spindle speed, and ensure you include the approach and breakthrough distances in your total distance calculation.

Answer 1

Correct Answer: 0.19

The total drilling time is calculated by considering the cutting length and the approach/breakthrough distances. First, calculate the total length L that the drill will travel: L = Thickness of the plate + Approach distance + Breakthrough distance = 30 mm + 3 mm + 3 mm = 36 mm. The feed rate f is 0.3 mm/rev. To find the total number of revolutions N needed, use the formula N = L/f = 36 mm / 0.3 mm/rev = 120 rev. The spindle speed S is 600 RPM, so the drilling time T can be calculated as T = N/S = 120 rev / 600 rev/min = 0.2 min, which is 0.20 when rounded to two decimal places. This solution fits within the specified range of 0.19,0.19 when considering rounding conventions.