Friction at the tool - chip interface can be reduced by

In a machining experiment, tool life was found to vary with the cutting speed in the following manner

The exponent $$(n)$$ and constant $$(K)$$ of the Taylor's tool life equation are

In a machining experiment, tool life was found to vary with the cutting speed in the following manner

What is percentage increase in tool life when the cutting speed is halved.

What are the upper and lower limits of the shaft represented by $$60{f_8}$$?

Use the following data:
Diameter $$60$$ lies in the diameter step of $$50-80$$ $$mm$$
Fundamental tolerance unit, $$i,$$ in $$\mu m = 0.45\,\,{D^{1/3}} + 0.001D,$$
where $$D$$ is the representative size in $$mm;$$ Tolerance value for $${\rm I}T8 = 25i,$$ Fundamental deviation for $$'‘f’'$$ shaft $$ = - 5.5{D^{0.41}}$$