NOTE: If you're not comfortable working with electrical component and AC power, then do NOT attempt this modification. Touching the wrong thing can potentially kill you.
Apparently most of the newer 7x12 mini lathes are now coming with a KBIC-240D speed controller stock. Unfortunately, mine was not one of them. While the power of my lathe is adequate, I wouldn't mind a little more torque, especially at low RPMs.
The lathe came stock with a PWM controller, and for the same reasons as with my mill, I decided to stick with a PWM controller for the lathe upgrade. Since installing the KBWS-25D in the mill went so well, I decided to do the same thing with the lathe. I eventually picked up a well used KBWS-25D on eBay for a great price. While the mill has a 350W motor, the lathe only has a 250W motor, so I installed a 9849 HP resistor on the KBWS.
NOTE: The older version of the KBWS-25D come with a very tall capacitor, while the newer versions come with a shorter one. The shorter one definitely makes mounting easier, especially on the mill.
 |
| My eBay find. |
The tall capacitor kept me from simply installing it in the control box, so I marked out the KBWS chassis on the exterior of the box and cut it out with a Dremel and some files. Then I used UHWM strips to space the KBWS out a little more and clean up the hole. The KBWS then slides in from the outside of the control box, and is bolted into place. If I was using a SCR controller from KB (like the KBIC or KBLC) then I could have just bolted it directly into the control box since they lack the tall capacitor of the KBWS. A hole was cut in the clear plastic protective sheet to provide clearance for the capacitor and the armature fuse holder was mounted to the side of the box.
 |
| Cuts and holes marked. |
 |
| Hole cut and drilled. It's not clean since I did it with my Dremel and the spacers will clean it up nicely. |
 |
| Bolted in place along with the spacers. |
 |
| Plastic cover and fuse holder mounted. |
Like in my mill, my lathe's wires are numbered which made things easier, though different lathe's might have different numbers or no numbers at all. For me, wire 1 (AC hot) went to L1, wire 2 (AC neutral) went to L2, wire 3 (motor +) went to A+, and wire 4 (motor -) went to A-. The potentiometer wires are in reverse order so P1 goes to P3, P2 to P2, and P3 to P1. I removed any extra wires I wasn't using to keep things clean.
 |
| Labeled connections on the KBWS. |
Since the mill doesn't come with a pre-installed run/off switch like the mill, I needed to add one to allow me to set a speed and then turn the spindle on and off independently. A mini toggle switch from Amazon worked nicely, and fit in the existing hole above the direction switch, and connected to the inhibit connectors on the KBWS.
The IR trim pot controls how much compensating voltage is given to the motor to maintain RPM, so I goosed it upward a little.
Like with the mill, I really like this mod. The board is more reliable, gives me much more control and adjustability, and allows me to set an RPM and then turn the spindle on and off. Considering if you bide your time you can find these boards for not too much, I think it's a great upgrade and definitely helps with the usability of the lathe.
How much did you pay for the controller
ReplyDeleteYou can buy one new on Amazon for $133.
DeleteQuestion; I am doing this modification, per your instruction and would like to know what is the armature fuse holder. Is it necessary? What exactily is it's function? Thanks, Pierre
ReplyDeleteIt holds a fuse between the controller and the motor. It should be used to protect the controller.
Deletehttps://www.kbelectronics.com/tech_bulletins/fusing-app-info.htm
Sorry, another question. Do you have the reversing switch working in your setup? Pierre
ReplyDeleteYes, since I still wanted the ability to run in reverse. It's wired between the controller and the motor.
DeleteSorry, back again. The controller will be working correctly, and then it will start to run full speed, sometimes it will revert back to the speed that was set. Sometimes when I try to open the box it will change itself. Very erratic. Do you have any suggestions for me to look at? Do need more information? Thanks, Pierre
ReplyDeleteInstead of me trying to troubleshoot it, I'd recommend giving KB Electronics a call. They have an excellent tech support department and will be happy to help you know. They know their equipment a lot better than I do.
DeleteI was curious on something. I'm ordering a G0765 Grizzly lathe and plan on making dies for reloading and other gunsmithing parts. I see a lot of people say you can't turn tool steel with these little lathes.
ReplyDeleteIs the motor controller a viable option to help low rpm torque with the factory motors? Or is this taken care of now in the new machines that are being sold.
I wouldn't say that's a matter of the motor/control, rather a matter of the lathe not being rigid enough to cut hardened steel very well.
DeleteI'm doing the KBWD-13 controller. It also has the inhibit function so when complete, it'll be able to set a speed and then turn the spindle on and off independently, same as yours.
ReplyDeleteBTW, similar to you, I picked up the board from ebay for better than half price.