GATE ME 2018 Set 2 — Question 59
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Manufacturing Processes → Machining & Machine Tools → Tool Life (Taylor's Equation)
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Question
Taylor’s tool life equation is used to estimate the life of a batch of identical HSS twist drills by drilling through holes at constant feed in 20 mm thick mild steel plates. In test 1, a drill lasted 300 holes at 150 rpm while in test 2, another drill lasted 200 holes at 300 rpm. The maximum number of holes that can be made by another drill from the above batch at 200 rpm is ______ (correct to two decimal places).
Correct answer
252 to 254
Solution
Taylor's tool life equation is given by .
Since the diameter of the drill is constant, cutting velocity (rpm).
The tool life is the total time spent drilling. For a constant feed and plate thickness , the time per hole is .
Total tool life , where is the number of holes.
Thus, .
Substituting into Taylor's equation: .
From Test 1 and Test 2:
Now for rpm:
The maximum number of holes is approximately 253.47.
Since the diameter of the drill is constant, cutting velocity (rpm).
The tool life is the total time spent drilling. For a constant feed and plate thickness , the time per hole is .
Total tool life , where is the number of holes.
Thus, .
Substituting into Taylor's equation: .
From Test 1 and Test 2:
Now for rpm:
The maximum number of holes is approximately 253.47.
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