CNC Lathe spindle motor – part 1 [Setup & Wiring]

In this blog, we will introduce, how we replace an electric motor and set up new components on a CNC lathe. All ideas for upgrading the CNC lathe spindle motor started with a new asset- CNC lathe in the company. New machine in our machine shop with the intention to improve our support even additionally and also with intention that we are making products for our development and needs. If you had problems with installing a new 3-phase electric motor and VDF (variable frequency drive) in the description you will find out all information for the proper setting.

Spindle motor before conversion

With the asset- CNC lathe (Prvomajska Tabturn 100), on the machine was installed an electric motor – 1 phase with power 250W and spindle RPM (4500 rpm/min) was extremely high for such type of machine. The electric motor had function ON/ OFF and change the direction of rotation spindle CW/CCW.

CNC Lathe spindle motor

3d Idea for CNC Lathe spindle motor

We decide to replace the electric motor. Upper data (4500 Rpm/min) were the base for choice. The spindle on our CNC lathe is not made for such high RPM. So we decide to set up a 3- phase asynchronous electric motor and VFD. The previous motor was 1- phase 250W. We selected 3 – phase electric motor,power: 550W,2-pole – 2740 RPM/min.

For the choice of the correct type of motor, we had two conditions: limitation with workplace and high power and torque. When the motor was chosen, was next step to correct reducing RPM with a pulley to make the correct ratio. The ratio in our case is 2:1, that’s means the pulley on an electric motor is 75mm and the pulley on the spindle is 150mm. Gear ratio 2:1 in our case means 1370 rpm/min on the spindle at line frequency 50 Hz. VFD makes it possible for us we can manage to reach higher or lower rpm.

CNC Lathe spindle motor 3d model

Setup new components on CNC lathe – Lathe setup

Below are the main components that we use it for the new CNC Lathe spindle motor setup. From the 3d model – we can see, that there we were also reduced with a place at an assembly. Assembly starts with the fastening of the holder of an electric motor. The holder has alignment holes which assist for an easier assembly and correct belt tension when the motor is fixed on the holder and the belt is on the pulley then we insure for correct belt tension.

3-phase asynchronous motor

Asynchronous motor: 2 pole – 2740 rpm/min – 50 Hz, power rating 0,55 kW.

VFD-Variable frequency driver


AC 1 phase 220 V input, AC 3 phase output, power rating 0,75 kW

Inverter Input filter


Inverter input filter. AC 1PH 220V, 50/60 Hz. The inverter input filter is recommended, inverter input filter reduce ripple effects

CNC Lathe spindle motor updated
vfd input filter

Wiring a new components

The below photo-wiring diagram presents connecting variable frequency drive to the electromotor. L/N and ground wires are connected to wire terminal blocks which are mounted in the CNC control box. In the wiring diagram, we can see the input filter, variable frequency drive, and 3- phase electric motor.

CNC Lathe spindle motor wiring

The diagram below – is the control wiring diagram. Control wiring diagrams include Variable frequency drive, Pokeys 57 CNC, and Relay.

wiring diagram

Additional information for CNC Lathe spindle motor

If you would like to measure current or observe the VFD motor control we offer oscilloscope current probe. To learn how to perform current measurement with oscilloscope check out our blog post.

Under download find Pokeys 57CNC user manual.

Finally, here you can check also the configuration for CNC lathe in Mach4.

Here is a complete explanation about the stepper motor driver.

Please also check our latest blog posts and products. It can help you to improve your machines or get some ideas on how to even make them better.

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