Sources and scope for this page: ISO 3002-1:1982, covering the definition of rake angle. No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
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.
Common misuse
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.