Brittle materials are machined with tools having zero or negative rake angles because it

During machining, the wear land $$(h)$$ has been plotted against machining time $$(T)$$ as given in the following figure.

For a critical wear land of $$1.8mm,$$ the cutting tool life (in $$min$$) is

In an orthogonal cutting test, the following observations were made
Cutting force $$=1200N ;$$ Thrust force $$=500N$$
Tool rake angle $$=zero ;$$ Cutting speed $$=1$$ $$m/s,$$
Depth of cut $$=0.8mm;$$
Chip thickness $$=1.5$$ $$mm$$

Friction angle during machining will be

In an orthogonal cutting test, the following observations were made
Cutting force $$=1200N ;$$ Thrust force $$=500N$$
Tool rake angle $$=zero ;$$ Cutting speed $$=1$$ $$m/s,$$
Depth of cut $$=0.8mm;$$
Chip thickness $$=1.5$$ $$mm$$

Chip speed along the tool rake face will be