7x10" Mini Lathe Replacement Speed Control Mount

This is a mount I designed to house a replacement speed controller module that I used to replace the OEM control board on my Harbor Freight 7x10" mini lathe. The OEM boards have a tendency to burn out really easily when under load, so dealing with the speed control for the motor, upgrading the motor, or otherwise powering the spindle ends up being an issue that owners of this kind of lathe have to deal with sooner or later. 

I didn't really feel like mucking around with re-soldering the burnt MOSFETs and the drop-in OEM replacements are way to expensive for what they're worth, so I opted to get a DC motor control off of Amazon for just under $30. I think these are generally made in the same factory, but a lot of them seem to be named “DC-51.” This solution also allowed me to repurpose all of the main wiring (including the grounds) between the motor and the power cord, so it's pretty convenient. 

CAUTIONS:

1. Ultimately, this is a high voltage wiring project, even if it is really simple. Do not try it if you're not a little familiar with wiring and and have a basic understanding of electricity, and always double check your work before plugging anything in. 
2. This project removes several of the safety features that come standard on these kinds of lathes. 
   1. For starters, you will not technically have an e-stop. The green switch in the pictures does function as a general shut-off, but note that this could be a change of workflow. 
   2. These lathes are often set up so that the potentiometer that controls speed must be first set to zero when the lathe is turned on before being able to start the motor. With this modification, if you leave the speed control potentiometer in one position and turn off the lathe, it will turn back on in that setting if you power the controller on. This could be very bad if you're in the process of chucking something in and are trying to multitask. Basically, you will need to be sure that you are always aware of the potentiometer's position before turning the lathe on, and it may be best to leave your lathe unplugged before you're ready to go. 
   3. At least for me, this process also meant removing the chip guard safety. 
3. This mod also means that you will not be able to reverse the motor direction as easily. That's not an issue for me personally as I don't mind rewiring things if I ever need to reverse the motor direction, but reversing the motor direction will no longer be a “convenient” thing to do.
4. Basically, I want to caution potential users of this project that it is NOT a drop in replacement for the OEM control board, and as such, it is a modification done at your own risk. Before doing this, you should be familiar with basic electrical wiring, and I would make sure that you are exceedingly familiar with your lathe and your workflow, as well as with general lathe safety before doing this. I would not recommend this if you are a novice with lathes and machine tools and/or you only just got your lathe. 
   The mini machines may not have the power of a full sized lathe, but accidents can still happen and these machines are not always as anemic as people make them out to be. Machine tool safety should be practiced on machines of all sizes, not just the full sized ones. 

PROJECT RECOMMENDATIONS/HARDWARE

• I printed with PETG-CF on a Bambu A1 mini at 7% infill for a majority of the part, and 20% for the part with the screw holes and the ears at the top of the part with the mounting holes. 
• You'll probably need to print this with supports for best results. 
• I made the holes at the top to accept an M4 brass threaded insert. You'll need two of those as well as two M4 screws to secure the speed control module to the mounting cage.
• You'll also probably need longer screws to screw the cage to the lathe. I used 10-24's, but use whatever you need. 
• There was also a plastic bracket attached to the lathe that I had to modify to allow for the cage to sit flush on the front of the lathe. I just used a rotary tool.