Rake angle

A schematic showing positive (left) and negative (right) rake angles.

In machining, the rake angle is a parameter used in various cutting processes, describing the angle of the cutting face relative to the workpiece. There are three types of rake angles: positive, zero or neutral, and negative.

  • Positive rake: A tool has a positive rake when the face of the cutting tool slopes away from the cutting edge at inner side.
  • Zero rake: A tool has a zero (or neutral) rake when the face of the cutting tool is perpendicular to the cutting edge at inner side.
  • Negative rake: A tool has a negative rake angle when the face of the cutting tool slopes away from the cutting edge at outer side.

Positive rake angles generally:

  • Make the tool more sharp and pointed. This reduces the strength of the tool, as the small included angle in the tip may cause it to chip away.
  • Reduce cutting forces and power requirements.
  • Helps in the formation of continuous chips in ductile materials.
  • Can help avoid the formation of a built-up edge.

Negative rake angles generally:

  • Increase the strength of the cutting edge. The tool is more blunt.
  • Increases the cutting force.
  • Increases the power required for a cut.
  • Can increase friction, resulting in higher temperatures.
  • Can improve surface finish.

Zero rake angles:

  • Easier to manufacture.
  • Easier to resharpen.
  • Less power and cutting forces than a negative raked tool.
  • Chip will wear and 'crater' the rake face.[1]
  1. ^ "Geometry of Single Point Cutting Tools". Scribd. Retrieved 23 November 2019.