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Back Rake

In the context of lathe tools, “back rake” refers to the angle of inclination of the top surface or face of the cutting tool relative to a plane parallel to the base of the tool:


  • Back Rake: It is the angle formed between the top surface of the cutting tool and a plane parallel to the base of the tool, measured in the vertical plane perpendicular to the cutting edge. This angle determines the orientation of the tool relative to the workpiece during machining operations.

Purpose and Effects:

  • Cutting Efficiency: Back rake helps in directing the cutting force in a favorable manner, aiding in efficient chip removal and reducing cutting resistance.
  • Tool Life: Proper back rake can extend the tool life by reducing wear and heat generation, especially in materials that are difficult to machine.
  • Surface Finish: It influences the surface finish of the machined part, with higher back rake often resulting in smoother finishes due to reduced friction and heat.

Types of Back Rake:

  • Positive Back Rake: When the top surface of the tool slopes upward toward the cutting edge, forming an acute angle with the base. This is common in turning tools and helps in effective chip evacuation.
  • Neutral Back Rake: The top surface of the tool is parallel to the base, resulting in zero back rake angle. This configuration is used in certain applications where minimal cutting force is required.
  • Negative Back Rake: The top surface slopes downward toward the cutting edge, forming an obtuse angle with the base. This angle is less common but may be used in specific cutting conditions where a strong cutting edge is needed.


  • Turning Operations: Back rake is critical in turning operations to optimize cutting performance, tool life, and surface finish. It is adjusted based on the material being machined, cutting conditions, and desired outcome.

Back rake plays a significant role in determining the cutting performance and efficiency of lathe tools. Understanding and optimizing this angle is essential for achieving desired machining results, whether in terms of surface finish, tool longevity, or cutting force management. Adjustments to back rake are made based on the specific requirements of the machining operation and the properties of the workpiece material.

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