What is a CNC Spindle – CNC Machine Tool Spindle Definition, Types and Uses | CNCLATHING


CNC spindle has a great impact on the performance of the machine tool. When we determine which spindle to choose, it’s essential to understand the spindle mechanism. In this article, we are going to talk about what is a CNC spindle and how it works on machine tools, as well as the common types of CNC spindle.

What is a CNC Spindle?

CNC spindle often refers to the shaft at the center of the rotating axis of the machine tools, sometimes spindle is used to refer to the entire rotary unit, including not only the shaft itself but its bearings and anything attached to it. Spindles rotate on the axis which receives input on movement from the CNC controller. Spindle is a very important part of a CNC machining center. The form of the spindle determines the speed and cutting force. A machine tool may have several spindles, the biggest one is called main spindle. Without further qualification, the spindle usually implies the main spindle. A diversity of configurations and options of spindles are available to meet the needs of different industries. Common examples are lathe spindle, milling machine spindle, grinding spindle, electric spindle, low-speed spindle, high-speed spindle, etc. 

What is CNC Spindle Used for

Machines containing spindles can be used in metalworking and woodworking, electrical component creation, and manufacturing CNC parts with various shapes. CNC machine tool spindle is used to drive the rotation axis of workpiece or tool. It offers the relative motion between the cutting tool and the workpiece which is essential to do the material removal. The spindle in CNC mainly plays the following functions:

– Provide constant power in a certain speed range to ensure sufficient cutting force.

– Positioning: make the spindle stop at a certain position accurately used for tool changing, boring tool withdrawing and special work requirement.

– Simultaneous tapping.

– Synchronous operation with the servo shaft; ensure the spindle rotates once, and the servo shaft moves a certain line.

– If there are multiple spindles in a system, two spindles can operate synchronously.

– Turn the spindle into a servo axis. 

Types of CNC Spindle - Which Type of Spindle Should You Choose?

There are many kinds of classification of CNC machining center spindle, different countries have different standards, there is a common classification according to the spindle taper, such as BT60, BT50, BT40, BT30, the number after BT represents the taper interface diameter of the tool holder. The machining centers that these different types of spindles can match are different. Due to the different diameters of the spindles, the rotation speed is different, which directly leads to the machining capability is different. 

1. BT30: spindle diameter is small, the maximum speed that can be achieved is higher than the spindle diameter. It is generally used in drilling and tapping center or some small machining center, and is most suitable for making mold and drilling and tapping. 

2. BT40: spindle diameter is medium, and the maximum speed is limited. A large part of machining centers uses BT40 spindle. This kind of spindle can be used for finishing or rough machining. It can also be used for the mold with a large drilling diameter, and its application range is the widest among these different types of spindle.

3. BT50 and BT60 generally do rough machining, the maximum speed is only 8000RPM, this kind of spindle is not commonly used in the CNC machining center.


High-speed spindles are the most common options in CNC machine shops, there are two types of high-speed spindles: integral motor spindle and belt-driven spindle. The integral motor spindle has a maximum speed of 60,000 RPM, which enables it capable of lots many machining needs but also limits the service life. The belt-driven spindle has a max speed of 15,000 RPM, it can achieve greater levels of power and torque, also lower in cost. High speed is ideal for cutting materials like aluminum, wood, and composite materials, when machining steel, stainless steel, and thermoplastics, high speed is not needed. We should choose a lower RPM spindle for steel processing, when you want to drill in steel, you should select a more powerful spindle.