I've been wanting a welding positioner for a while now and just didn't want to cough up the price that the market commands. A decent entry level one is ~$1400 and they easily go up to $3000 without going overboard on size and features. Even a medium sized Chinese model is $900 after shipping... Ugghh... So I decided to build one. I started with a 2" OD spindle to have a large "thru" bore. 2-1/4"-8 threaded snout for common availability chucks. After welding the snout tot he spindle, I chucked it up in my lathe to recut the shoulder square. Next, I started on the frame using 1" square tubing. Next, I made a captured, spring-loaded locking pin. The pin is machined from 304. I chose to make the sprocket removeable in case I ever needed to change the ration or service the pillowball block. So I welded a split collar to it to make it a bolt-on affair. Onto the electronics. The motor is a NEMA 23 stepper motor. Not incredibly powerful, but very precise. And I get a 3:1 torque multiplication using sprockets to help get the power that I need. It's all controlled by a Arduino microprocessor. I bench tested everything and programmed the Arduino prior to mounting it all in a box. Once I verified it all worked, it was onto the junction box. I chose a plastic box so that it would isolate the electronics from the frame. The motor itself is also isolated from the frame using plastics. As you can see, it all barely fits. Perfect. 120v comes into the box, the power supply steps it down to 24v for the motor. And I also have a separate power supply to step the 120v down to 5v for the Arduino and LCD display. I had a front panel machined and laser engraved. It was wither this or drilling holes through plastic and using my label maker - this panel gave it a nice finishing touch. And after priming and painting the frame and reassembly, here is the final product. Grounding is achieved by wrapping a nickel-plated grounding strap around the spindle. it's held tight with a spring and I have a 4-ga wire traveling from it down to a brass post. This helps keep my welding clamp low and out of the way. Speeds are adjustable between 0 and 10 RPM, in .1 rpm increments.