I try to make Flexible Shaft Dremel Tool With 12V 15A Switching PSU. I use 775 motor, 30A DC motor speed controller,12V 15A Switching PSU. At here I will tell you detail about of 30A DC mottor speed control and 2V 15A Switching PSU.
You can download all file here PCB,Schematic,Gerber file for you can order PCB online. I alway upload gerber file to https://jlcpcb.com/m for get PCB with only 2$for 10PCB
https://drive.google.com/file/d/1UELsHSTSvypJEKCCTmfQs_MVGCwQmbUv/view
I had video and instructable about 24V DC Motor Speed Controller. You can check here. But the great thing it can run with 12V for 12V DC motor with little bit modify. Look the picture and schematic i had modify for run at 12V. At my project i use mosfet irfp240 without heatsink when run 775 motor at max speed it warm. You can use IRFz44 or IRF3205 but need small heatsink
The Schematic, PCB,Gerber file you can download here and make it by yourself .
small heatsink for 2 mosfet ( can take from old PC powersupply)
for more detail copy and paste to google image search
I have video and instructable about it you can check here. But the output is 24V so we need modify little bit for make 12V output. Normally. A transformer without CT PIN of PC PSU had 2 output voltage 12V, 5V ( 3.3V take from 5V pin). For get 24V we use 12V output pin and for get 12V we choice 5V pin. You can download the Schematic, PCB gerber file for make by yourself.