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, negative, and neutral.

POSITIVE RAKE:-A tool has a positive rake when the face of the cutting tool slopes away from 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.

Generally, positive rake angles:

  • 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, by contrast:

  • Make the tool more blunt, increasing the strength of the cutting edge.
  • Increase the cutting forces.
  • Can increase friction, resulting in higher temperatures.
  • Can improve surface finish.

A zero rake angle is the easiest to manufacture, but has a larger crater wear when compared to positive rake angle as the chip slides over the rake face.[1]

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

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