Question

A high-speed tool steel is used for machining of a workpiece of mild steel While machining at cutting speed of 30 m/min, the useful tool life of tool steel is found to be 1 hr. What will be the tool  life  if  the same tool is used  to cut  at  a speed of  40 m/min. ? (Assume n = 0.12)
1. 5 min
2. 5.75 min
3. 6 min
4. 5.5 min

Answer 1

Correct Answer - Option 4 : 5.5 min

Concept:

Taylor's tool life equation is:

VTⁿ = Constant

where V = cutting speed m/min, T = tool life in min

Calculation:

Given:

T₁ = 1 hr = 60 min, V₁ = 30 m/min, V₂ = 40 m/min, n = 0.12

V₁T₁ⁿ = V₂T₂ⁿ = Constant

V₁T₁ⁿ = V₂T₂ⁿ

30 × (60) ^0.12 = 40 × (T₂) ^0.12  

\(\frac{{30}}{{40}} = {\left( {\frac{{{T_2}}}{{60}}} \right)^{0.12}} \Rightarrow {T_2} = 5.45\min \approx 5.5\;min\)