The angle between the tool's cutting face and a line perpendicular to the machined surface.
Rake angle controls how the chip forms and how much force the cut takes. A positive rake presents the cutting edge at an angle that slices into the material, reducing cutting force and power consumption but weakening the edge. A negative rake presents the edge bluntly, which strengthens it at the cost of higher forces and more heat.
The practical split follows the material: aluminium and plastics take positive rake for their low cutting forces; hardened steel, cast iron and interrupted cuts take negative rake because edge strength matters more than force. Most indexable inserts are negative-rake for this reason, which is why they can be turned over and used on both faces.
Confusing rake angle with clearance angle. Rake faces the chip; clearance faces the machined surface. Swapping them produces a tool that rubs instead of cutting — a common cause of poor finish and rapid edge failure.
This site uses Google Analytics to count visits and see which pages are useful. It sets cookies only if you agree. See the privacy policy.