Rake angle

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

Rake angle is a parameter used in various cutting and machining processes, describing the angle of the cutting face relative to the work. 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:

  • Increasing 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]

Recommended rake angles[edit]

Recommended rake angles can vary depending on the material being cut, tool material, depth of cut, cutting speed, machine, setup and process. This table summarizes recommended rake angles for: single-point turning on a lathe, drilling, milling, and sawing.

Material being cut Turning Rake [2] Drilling Rake [3] Milling Rake [4] Sawing Rake [5]
Aluminum 12°-25° 40° 35° 12°-25°
Brass 3°-14° 3°-14°
Bronze 5°-14° 5°-14°
Cast Iron, Gray 0°-6° 3°-6°
Copper 18°-25° 16° 18°-25°
Polystyrene 20°-25° 20°-25°
PVC 20°-25° 20°-25°
Stainless Steel 8°-10° 8°-10°
Steel, Mild 12°-14° 20° 8°-15° 12°-14°
Titanium 0°-4° 0°-4°

References[edit]

  1. ^ "Geometry of Single Point Cutting Tools". Scribd. Retrieved 23 November 2019.
  2. ^ "Rake Angle Versus Material". Thread Check Inc. Retrieved 24 November 2019.
  3. ^ http://mmu.ic.polyu.edu.hk/handout/0102/0102.htm[dead link]
  4. ^ "Grinding HSS lathe tools". Steve's Workshop. Retrieved 24 November 2019.
  5. ^ "Rake angle vs material chart" (PDF). Regal Cutting Tools. Retrieved 24 November 2019.