Cutting Speed vs Cutting Velocity: Difference and Comparison

Key Takeaways

1. Cutting speed is the relative velocity between the cutting tool and the workpiece material during the cutting process.
2. Cutting velocity is the speed at which a specific point on the cutting tool’s edge moves relative to the workpiece during cutting.
3. Cutting speed has scalar quantity as it only has magnitude and lacks direction information while cutting velocity has vector quantity, which includes both magnitude and direction.

What is Cutting Speed?

Cutting speed refers to the relative speed between the cutting tool and the workpiece material during the cutting process. It is measured in surface feet per minute (SFM) or meters per minute (m/min). The cutting speed directly affects how fast the cutting tool moves across the work piece’s surface, engaging the material and removing unwanted material to shape the final product.

The cutting speed is influenced by various factors- including the material, the type of cutting tool, and the specific machine operation. In general, harder material requires lower cutting speeds to prevent excessive tool wear and heat generation, while softer materials can withstand higher cutting speeds for increased productivity.

Manufacturers determine the ideal cutting speed based on extensive research, experience, and cutting data charts, considering the material’s hardness, workpiece dimensions, and the desired surface finish. 

What is Cutting Velocity?

Cutting velocity represents the speed at which the cutting tool’s outermost point cutting edge moves through the workpiece material. It is measured in feet per minute (FPM). Higher cutting velocities can lead to more material being removed in a given time, influencing the efficiency and productivity of the process.

It is essential in various machining operations like turning, milling, drilling and grinding. It is determined by considering several factors, such as the material’s hardness, workpiece material, tool material, depth of cut, and the desired surface finish. Different materials require different velocities. For example- softer materials like aluminium may require higher cutting velocities, while harder materials like stainless steel may need slower cutting speeds.

Higher cutting velocities are advantageous for achieving faster material removal rates, reducing cycle times, and increasing productivity. At the same time, lower cutting velocities reduce productivity and increase the risk of built-up edge-up formation.

Difference Between Cutting Speed and Cutting Velocity

1.  Cutting speed refers to the rate at which cutting tool moves relative to each other in the cutting process while cutting velocity denotes the actual speed and direction of the cutting tool’s movements in three dimensions.
2. Cutting speed is expressed in surface feet per minute (SFM), while cutting velocity is represented in feet per second.
3. Cutting speed only considers the relative motion between the cutting tool and the workpiece in the cutting plane, while cutting velocity considers the direction of the cutting tool’s movement in all three dimensions.
4. Cutting speed is easier to adjust and control as it focuses on a single plane’s motion while cutting velocity requires more sophisticated control and analysis due to its three-dimensional movements.
5. Cutting speed has scalar quantity as it only has magnitude and lacks direction information while cutting velocity has vector quantity, which includes both magnitude and direction.

Comparison Between Cutting Speed and Cutting Velocity

Parameters	Cutting Speed	Cutting Velocity
Definition	The rate at which cutting tool moves relative to each other	The actual speed and direction of the cutting tool’s movements in three dimensions
Measurement Units	SFM (surface feet per minute)	Feet per second
Direction	Only considers the relative motion between the cutting tool and the workpiece.	Considers the direction of the cutting tool’s movements in all three dimensions
Adaptability	Easier to adjust and control	Requires more sophisticated control
Quantity	Scalar	Vector

References

1. https://asmedigitalcollection.asme.org/IMECE/proceedings-abstract/IMECE2001/115/1123957
2. https://www.sciencedirect.com/science/article/pii/S0924013601009979