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In an orthogonal machining with a single point cutting tool of rake angle 10°, the uncut chip thickness and the chip thickness are 0.125 mm and 0.22 mm, respectively. Using Merchant’s first solution for the condition of minimum cutting force, the coefficient of friction at the chip-tool interface is _____ (round off to two decimal places).
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- 0.7355
- 0.74
- 0.243
- 0.144
Correct Option: B
t = 0.125 mm tc = 0.22 mm
rake angle, α = 10°
| Chip thickness ratio , r = | ||
| tc |
| r = | = 0.568 | |
| 0.22 |
| tanφ = | ||
| 1 - rsinα |
| tanφ = | ||
| 1 - 0.568sin10° |
Shear angle φ = 31.83°
| 2φ + β - α = | = 90° | |
| 2 |
⇒ 2 × 31.83 + β – 10 = 90°
Friction angle β = 36.33°
∵ tan β = μ
⇒ Coefficient of friction, μ = tan36.33 = 0.7355°
μ = 0.7355 ≈ 0.74
