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A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev. The required approach and over run of the drill together, is equal to the radius of drill. The drilling time (in minute) is
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- 1.00
- 1.25
- 1.50
- 1.75
Correct Option: B
| T = | |
| fN |
L = t + Ap1
Ap1 = 0.5 D (holes diameter)
= 10 mm
t = 40 mm
| T = | = 1.25 min. | |
| 0.1 × 400 |
