mark-NJ
Well-known member
To be clear, I'm not a pro welder. But my TIG work is getting better & better and I'm enjoying the practicing and the occasional hired project work. Lately I've wondered if it would be nice to have a turntable for doing "round" work.
I don't like the cheap ones I see, because they all seem to run the ground through the bearings, and I can't see that being a good long-term design. And the expensive ones are just out of my financial reach, from a justification perspective. So I set about to make one. The ground rules were: It had to be variable speed, it had to handle up to 5" diameter stock, it had to handle about 50 pounds of stock weight, and it had to cost less than the cheepo units seen on Amazon for about $250.
- I found some steel plates in the dumpster at work, and I have some scrap bedframe angle iron. I have 5/16" & 1/2" rod stock on-hand, too.
- I bought the least expensive 12VDC windshield wiper gear motor I could find on Amazon for $32 bucks
- I spent about $50 bucks on groove belts & pulleys & thrust bearings on Amazon...the kind used for 3D printers.
- I found a brand new 5" lathe chuck on Craigslist for $25 bucks
- I bought a small PWM speed controller on eBay for $21 bucks
- I bought some 1/2" bronze bushings, thrust bearings & shaft stops from McMaster...about $30
It's just tacked together right now, serving as a proof-of-concept, but this thing works REALLY well! I built this as a prototype, but frankly, I'm tempted to finish up the welds & hit it with some paint and call it "done".
Ain't "pretty", but it isn't altogether ugly, either!
The motor, with 12VDC applied, turns about 48RPM. I don't know what the internal reduction is, but the main shaft has serious torque. The thread was 8mm x 1.25, so step one was to see if I could drill & tap the 20-tooth aluminum pulley. Easy-peasy!
Next was to make a reduction rack...a couple of steel plates, a few holes drilled, a few bronze bushings, a few thrust bearings....done! Motor to the last pulley on that little rack is 16:1.
Lastly was the main shaft. The final reduction is 2:1, giving the entire thing a 32:1 reduction. These may be cheap little aluminum pulleys, but you CANNOT stop the mainshaft! Mainshaft is 1/2", and is guided by bronze bushings....1/2" ID, 3/4" OD. I bought two 3/4" nuts, drilled them to 3/4, and welded the nuts to the plates. The bronze bushings ride in place, and all downward force is supported top & bottom on 3-piece thrust bearings.
The mainshaft is welded to a 6" dia plate to which the chuck is bolted. My groundclamp goes right on the mainshaft (it doesn't bog the shaft whatsoever)...but I may modify this with some sort of wrapped-braid ground system.
Speed control was fun...cheap PWM controllers are available everywhere, so I grabbed one. I had a Husky plastic organizer box kicking around doing nothing, so I decided to dedicate it to the cause. The controller came with a speed pot, directional switch & LED tach attached. The tach was pointless, as my reduction gearing rendered it grossly inaccurate, so I jettisoned it. The speed pot was a mini pot 100KL, and I have some full-size pots of that value left over from my guitar amp manufacturing days, so I switched that out. Power in, I used banana posts, and power out is a Cannon XLR plug.
I had to extend the wires on the controller for all of that, but that's easy....solder & shrinkwrap. Voila!
On the original mini pot, there was an on-off switch which stops the output voltage immediately via dynamic braking. This got me to thinking: it may be good to develop the weld puddle before the turntable moves, so I re-routed these on-off leads from the pot to a 1/4" shorting jack. I TIG with a footpedal, so I have a couple of fingerswitches kicking around doing nothing. I put a 1/4" plug on one, taped it to my torch, and now I can control the motor with my index finger!
The PWM controller needs 12VDC: I'm in the process of disposing of an old computer, so I have a regulated PS available, but for now I'm just using my boat battery:
I'm not convinced that the motor completely loves the PWM, but this isn't an 8-hour per day production machine, so it will be fine for my infrequent use. I can spin the turntable from creeping (barely moving) to about 1.5 RPM. I've done a few practice welds on it (pipe to fittings, etc.) and this thing works far better than I ever could have anticipated!
So that's my story & I'm sticking to it!
Comments & criticism (constructive or otherwise) is appreciated,
I don't like the cheap ones I see, because they all seem to run the ground through the bearings, and I can't see that being a good long-term design. And the expensive ones are just out of my financial reach, from a justification perspective. So I set about to make one. The ground rules were: It had to be variable speed, it had to handle up to 5" diameter stock, it had to handle about 50 pounds of stock weight, and it had to cost less than the cheepo units seen on Amazon for about $250.
- I found some steel plates in the dumpster at work, and I have some scrap bedframe angle iron. I have 5/16" & 1/2" rod stock on-hand, too.
- I bought the least expensive 12VDC windshield wiper gear motor I could find on Amazon for $32 bucks
- I spent about $50 bucks on groove belts & pulleys & thrust bearings on Amazon...the kind used for 3D printers.
- I found a brand new 5" lathe chuck on Craigslist for $25 bucks
- I bought a small PWM speed controller on eBay for $21 bucks
- I bought some 1/2" bronze bushings, thrust bearings & shaft stops from McMaster...about $30
It's just tacked together right now, serving as a proof-of-concept, but this thing works REALLY well! I built this as a prototype, but frankly, I'm tempted to finish up the welds & hit it with some paint and call it "done".
Ain't "pretty", but it isn't altogether ugly, either!
The motor, with 12VDC applied, turns about 48RPM. I don't know what the internal reduction is, but the main shaft has serious torque. The thread was 8mm x 1.25, so step one was to see if I could drill & tap the 20-tooth aluminum pulley. Easy-peasy!
Next was to make a reduction rack...a couple of steel plates, a few holes drilled, a few bronze bushings, a few thrust bearings....done! Motor to the last pulley on that little rack is 16:1.
Lastly was the main shaft. The final reduction is 2:1, giving the entire thing a 32:1 reduction. These may be cheap little aluminum pulleys, but you CANNOT stop the mainshaft! Mainshaft is 1/2", and is guided by bronze bushings....1/2" ID, 3/4" OD. I bought two 3/4" nuts, drilled them to 3/4, and welded the nuts to the plates. The bronze bushings ride in place, and all downward force is supported top & bottom on 3-piece thrust bearings.
The mainshaft is welded to a 6" dia plate to which the chuck is bolted. My groundclamp goes right on the mainshaft (it doesn't bog the shaft whatsoever)...but I may modify this with some sort of wrapped-braid ground system.
Speed control was fun...cheap PWM controllers are available everywhere, so I grabbed one. I had a Husky plastic organizer box kicking around doing nothing, so I decided to dedicate it to the cause. The controller came with a speed pot, directional switch & LED tach attached. The tach was pointless, as my reduction gearing rendered it grossly inaccurate, so I jettisoned it. The speed pot was a mini pot 100KL, and I have some full-size pots of that value left over from my guitar amp manufacturing days, so I switched that out. Power in, I used banana posts, and power out is a Cannon XLR plug.
I had to extend the wires on the controller for all of that, but that's easy....solder & shrinkwrap. Voila!
On the original mini pot, there was an on-off switch which stops the output voltage immediately via dynamic braking. This got me to thinking: it may be good to develop the weld puddle before the turntable moves, so I re-routed these on-off leads from the pot to a 1/4" shorting jack. I TIG with a footpedal, so I have a couple of fingerswitches kicking around doing nothing. I put a 1/4" plug on one, taped it to my torch, and now I can control the motor with my index finger!
The PWM controller needs 12VDC: I'm in the process of disposing of an old computer, so I have a regulated PS available, but for now I'm just using my boat battery:
I'm not convinced that the motor completely loves the PWM, but this isn't an 8-hour per day production machine, so it will be fine for my infrequent use. I can spin the turntable from creeping (barely moving) to about 1.5 RPM. I've done a few practice welds on it (pipe to fittings, etc.) and this thing works far better than I ever could have anticipated!
So that's my story & I'm sticking to it!
Comments & criticism (constructive or otherwise) is appreciated,
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