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A 31.8 MM HSS drill is used to drill a hole in cast iron block 100 mm thick at cutting speed of 20 m/min and feed 0.3 mm/rev. If the over travel of drill is 4 mm and approach 9 mm, the time required to drill the hole is
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- 1 min 40 s
- 1 min 44 s
- 1 min 49 s
- 1 min 53 s
Correct Option: D
D = 31.8mm, t = 100 mm, V = 20m /min
f = 0.3 mm/rev,
Approach length = 4 mm
Over Travel = 9 mm
| Time/ hole = | = 1 min 53 sec. | |
| 0.3 × 200 |
