Convert a lathe to variable speed drive for under $100
Here's a few photos and some videos to show that something is happening to my CQ9325 bench lathe. It now has VSD (variable speed drive) fitted.
a 1.5 HP DC treadmill motor, DC drive controller,
and a LED tachometer with Hall effect sensor.
This conversion is great for light to medium turning, but heat rise in non SCR rated DC motors like this is a problem when pushed hard.
Be aware that a serious cooling system is required to keep things under control when revs drop and the motor is applying full torque.
Being a brushed motor, voltage duration to windings increases as speed drops, and this will cause significant heat rise.
The two PC case fans I fitted were not sufficient, and something like a small inline bilge blower for a boat may be required for heavy use.
I got this great blower
cheap, but it's way too noisy, so I used it for my backyard
furnace, and the hunt goes on. Maybe a 12 volt car dash
blower would do the job.
The reversing switch is now gone and in it's place is the speed control.
For the VSD conversion you need two main things
A junked/recycled DC treadmill motor of suitable horse power.
And a secondhand (or new) DC drive controller, such as this KB Electronics KBIC-240
And a few other bits and pieces including:
- 1 three wire 5K ohm linear potentiometer (type B),
- 1 or 2 PC case cooling fans,
- 1 240 V or greater, three pole toggle switch,
- 1 junked mains wall power pack of 12 volts DC,
- 1 junked XT PC power case or small metal tool box,
- 1 AC power outlet (unswitched),
and if you want to install a tachometer
- 1 LED tachometer display,
- 1 Hall sensor.
Here's some videos of the completed installation
And the lathe in action machining some medium carbon solid steel stock.
The DC controller is using the factory trim pot settings.
Here's an overview of the KBIC-240 controller.
maximum motor speed is set at the recommended 60%. This
best use of available torque, and provides the greatest motor
ranges of 0 - 2000, 0 - 800, and 0
- 250 RPM provide adequate power and torque.