Welding turntable

Hi,

From time to time I have seen mention of welding turntables. I want to build my own turntable. I have a suitable piece of 3/8" plate and a large "lazy susan" bearing. The problem, of course, is obtaining a reliable, low-resistance grounding connection. At one point I think I saw a post from Ernie mentioning the use of carbon brushes such as those used in commutator motors, but I have not had much luck finding brushes with shunts that could potentially handle 200A, even if I used multiple blocks. I suppose I might use carbon rods such as those used for carbon arc gouging, or perhaps there are suppliers of replacement brushes for large DC motors. If so, I haven't found them. My usually reliable sources such as McMaster and Grainger have not been helpful this time.

Another possibility is a spring loaded copper stud that bears against the underside of the table. This seems to suffer from a high likelihood of oxidation and arcing leading to a high-resistance connection. Even a few ohms is too much. Then again, maybe it would be ok - I really am not sure.

So, for those of you who have seen commercial turntables or who have built your own turntables: How was the grounding connection made?

Thanks in advance for any useful info you can provide.

"Joe Blow"

Reply to
Joe Blow
Loading thread data ...

The small turntable we have at school uses a large carbon motor brush that rubs against the shaft the plate is mounted to. The shaft and bearings are completely insulated otherwise so the power can only ground through the brush.

Remeber that when using a turntable, it only has to rotate once to complete a weld. A simple large copper bar sprung against the underside of the plate would work fine.

Reply to
Ernie Leimkuhler

So why not use a couple of very loose wraps of cable or heavy grounding brid for the connection?

Ted

Reply to
Ted Edwards

formatting link
Joel. phx

Reply to
Joel Corwith

I made one a while back that consisted of a 3" thick and 12" or so diameter round piece of steel with a blind hole on the underside that rode on an old dividing head or superspacer base and what I did for my ground was use a flat magnet ground adapter from Harbor Freight that slid along the bottom which was flat and I welded a inner and outercircle made out of OA welding wire on the bottom and mounted a little bar to the base that kept it in one place so my cable did not wrap and the magnet just slid along the bottom. The center contact of the magnet ground clamp is brass so it made a good contact. I think I paid about $10.00 for the magnetic ground clamp.

Sam

Reply to
sam

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.