Rake angle
In machining, the rake angle is a parameter used in various [cutting Tool bit|tool (machining)|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 the inner side.Zero rake: A tool has a zero rake when the face of the cutting tool is perpendicular to the cutting edge at the 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 the 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.
- 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.
- Easier to manufacture.
- Easier to resharpen.
- Less power and cutting forces than a negative raked tool.
- Chip will wear and 'crater' the rake face.
Recommended rake angles
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 | Drilling Rake | Milling Rake | Sawing Rake |
| Aluminum | 12°-25° | 40° | 35° | 12°-25° |
| Brass | 3°-14° | 8° | 0° | 3°-14° |
| Bronze | 5°-14° | 0° | 5°-14° | |
| Cast Iron, Gray | 0°-6° | 0° | 5° | 3°-6° |
| Copper | 18°-25° | 16° | 18°-25° | |
| Polystyrene | 20°-25° | 20°-25° | ||
| PVC | 20°-25° | 20°-25° | ||
| Stainless Steel | 8°-10° | 8° | 8° | 8°-10° |
| Steel, Mild | 12°-14° | 20° | 8°-15° | 12°-14° |
| Titanium | 0°-4° | 0°-4° |