Cutting Speed vs. Spindle Speed: What Is the Difference

When you first start out in a machining shop, you will be introduced to a lot of jargon and shorthand. Between Jo Blocks, dovetails, and chucks, it’s like learning an entirely new language. On top of that, every individual machine has a long list of specific terms.

For instance, if you were to look up the speed of a machining tool, you may find a plethora of different numbers that all mean something different. For example, there is cutting speed vs. spindle speed. What is the difference? Knowing that information will help you know your machine and what it’s capable of.

What Is Cutting Speed?

Cutting speed refers to how quickly a machine can cut through material. If you compare a machining machine to a car, this would be how fast a car travels, or its miles per hour. Most likely, you aren’t cutting through miles of material, so typically we measure cutting speed in surface feet per minute (SFM).

What Is Spindle Speed?

Spindle speed, on the other hand, refers to the rate at which the spindle rotates, or how many times it spins in a designated amount of time. If we went back to the car analogy, this would be comparable to how many times the tires spin. We measure this in rotations per minute, or RPM.

Pro Tip: Doing the Math

If you can find one of these numbers, then you can find the other using a simple equation. That equation is RPM = SFM ÷ diameter × 3.82. With basic algebraic principles, you can solve for either RPM or SFM, as long as you have the other value and the diameter of the spindle. Whatever each number is, they will be proportionate to each other.

The Significance of Cutting Speed and Spindle Speed in Machining

Naturally, knowing how fast your machine will be able to cut through material will give your company valuable insight into how long it will take to complete a task. However, greater speed isn’t always ideal, especially when you consider friction.

Friction between two objects creates heat. The more speed, the higher the friction. The higher the friction, the higher the heat. And the speed at which the spindle moves and the speed it moves along the material both impact friction separately. Prolonged exposure to high heat can wear down a spindle. So, it’s crucial to balance efficiency with the need to preserve the equipment.

Knowing the difference between cutting speed and spindle speed will help your company know your machinery. And if you want to make sure your spindles are in top condition, Industrial Automations has the CNC spindle motors you need to keep your machinery running.