Difference between Positive and Negative Rake Angles
| | Positive Rake Angles | Negative Rake Angles |
1. | A positive rake angle is a top rake angle of less than 90° | A negative rake angle is a top rake angle of 90° or larger. |
2. | A positive rake angle to cut hard materials such as cast iron. | A negative rake angle to remove large amounts of material. |
3. | Positive rake angle, the leading edge of the cutting tool is behind the perpendicular of the material to be cut. | Negative rake angle while the tool leading edge is ahead or beyond the perpendicular of the material to be cut. |
4. | A positive rake angle tends to pull the work towards the blade this is desireable in a table saw as that also pulls the work down onto the surface of the table. | A negative rake angle on the other hand tends to push the work away from the blade which is desireable in a radial arm saw because it pushes the work towards where it is being supported. |
5. | The positive rake angle cause the face of the cutting tool to slant downward when moving away from the cutting edges. | The negative rake angle cause this surface to slant upward when moving away from the cutting edge. |
6. | Positive rake angle are less cutting force. | Negative rake angle are more cutting force. |
7. | Positive rake angle should be used whenever possible for all types of high-speed steel milling cutters. | Negative rake angle are frequently employed to provide more material back of the cutting edge to resist shock loads. |
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