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Good Ground connections for welding

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When using a metal welding table, clamping the ground to the table work, and makes the entire table the ground. Place the work on the table, hit it with the stinger and go.

For some projects the current does not flow as well as I would like. What is your opinion of making a extension to go from the original grounding clamp to another (secondary) grounding clamp that can be attached directly to the project, or close to the weld zone? This could be nothing more than a set of jumper cables, clamp one end to the original grounding clamp and the other to the work.

Is this feasible to improve the grounding?

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Either way should work, clamping to the workpiece directly or to the steel table-- unless the workpiece itself is not getting good contact with the table. I think a jumper would add to the clutter, introduce new variables (ampacity? good connections?) that might even reduce amperage. Also, that mystery (to me, anyway), arc blow, can be a problem if your ground is too close to the stinger.

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Hi Glen. I think that this is a great idea. I will give it a try.

By the way, conductances add, so this will always lower the resistance. For example, adding pipes to a network (fully developed flow) always improves the rate. Note that this does not apply for incompletely developed flows, for example, adding extra inlets to a naturally aspirated burner.

The arc blow problem is a valid one. Still worth a try.

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I was thinking about two different applications.

One lack of good ground with the table due to dirt or whatever. Attach the extra cable and your good to go. A little help from a friend so to speak.

The other is if you are using some type insulating material between the work and the table such as rubber tires on a lawn mower being repaired. No use disconnecting the "good ground" to the table. Just add a jumper.

My concern was the way the electric flowed and if it would effect the weld or the welding machine. I never did understand how 4-5-or more welders could be connected to a common grounding clamp and one lead going to the work where several stingers were being used. (Large fabrication with several welders working at the same time). When ask how the electric found it's way back to the right machine to complete the circuit, I was told not to worry about it. (grin).

Again the jumper is NOT made from 18 ga lamp cord, but made from REAL welding cable, using REAL welding clamps.

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Covforge is exactly correct.

If you use a table for a ground make absolutely 100% certain that is a bullet proof ground from the table to the welding ground.

Or you might be a dissapointed owner of a power tool that used to work.

If the tool is grounded it may be an easier ground path than the table. Thus the 10 amp tool or whatever it is may see a full 150 amps of welding current releasing the factory installed smoke.

Please note: once the factory installed smoke is released it is almost impossible to re-install the smoke and make the tool run again.

The same principal applies if you are welding on a truck bed or other equipment that should be grounded and you lay a power tool down, creating an alternate ground path for the welding current thru the tool.

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For some reason the welding table is not imparting good ground to the work

So, if the welder and the welding table are stationary (have not been moved is 6 months or more) would it be a good idea to run a grounding clamp to the welding table and bolt it to the table?

Or put a terminal on the end of a short piece of welding cable and bolt it to the welding table. The other end of the short piece of welding cable would have a quick disconnect to fit the welding lead.

I know, KISS and simple is best, and this is getting complicated real fast.

I have checked the lead connections (good contact at the welder, grounding clamp and stinger), used a grinder to get bare metal at the ground connection point, and even wire brushed the slots in the stinger. That leaves the problem at the table / project contact point. Or am I missing something?

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As long as the wire is heavy enough to carry the required amperage, it will be perfectly ok without dropping the amperage. I have a chart here somewhere that tells the max length for the max amps in both aluminum and copper wires. When i find it, I'll post the chart. It goes up to like 500 feet or something like that.

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So you haven't moved the welder or the table in the past 6 months?
Nothing has been changed in the power supply to the welder?
Are you getting adequate voltage to the welder?

We once had a situation in which we thought every appliance in the house and my arc welder were on the 'blink'.......turned out the power company's transformer on the pole was going bad.

If the welder performs properly when the table is not involved with the circuit, one would think the table would be the problem.

"Resistance" could be part of the problem

If the 'route to ground' on the table is excessively long........and the table has sufficient mass, there could be problems.

Resistance is the main reason your not supposed to use a 500 ft. extension cord.

I would try the jumper and see if it helped........I don't think it could hurt anything, and might help diagnose the problem.

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I would certainly use a bolted connection to a welding table I use regulaly to minimize the hazard of frying a power tool as was discussed earlier.

One of the other problems is that most of the "consumer" type welders, (Lincoln 225, Miller Bobcat etc) have a lower open circuit voltage than production welders. This was done for safety reasons.

This makes it harder to establish a ground as there is less "sparking power" to cut throught the dirt, rust, paint, etc with one of these welders.

With a production welder, it has the voltage to burn through more of the dirt etc and establish a ground.

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You ground the rust away from the top of the table.
Did you place the grounding clamp with the jaw that has the cable bolted to it on the cleaned area or on the underside where it did not get clean?
If it's a brass grounding clamp is the jaw of the clamp that has "this side up" attached to the clean area? This is also the side that the cable bolts into.
If it's a brass clamp is the contact surface clean or does it have arc marks and burned places on it?
Does the cleaned table and the clean (no paint, rust, slag, etc.) item being welded do OK for a while before starting to have problems while welding? Slag and spatter between the item being welded and the table will act like insulation.
Even with a shiny table top the item to be welded can start to vibrate while welding. Amazing as it sounds, the contact point between table and item to be welded will heat up. The metal will expand and move in this tiny area. An arc will be observed as the metals move and when they move far enough the arc is extinguished. Metals move back together and it repeats. This can happen in rapid succession when tig welding and the item being welded starts to vibrate like a door bell without the ding dong.
The electrode holder has been cleaned. Does the electrode fit tightly?

When a ganged or multiple welding machine is used there is usually no problems with the arc knowing which weldor to go to or how to complete a circuit.

Most all of them have a GPS now days.
Big toothy grin!

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  • 3 weeks later...

Jnr briefed me on constructing my welding table. I just have the ground from the permanently installed welder bolted to the table. Actually the table is welded to some 2" angle which is attached to the wall by rawlbolts. The ground is simply connected to the nut holding one of the rawlbolts in place. I never have a problem and do quite a bit of welding.

Why not just include ground straps on the clamps you use when holding work together prior to tacking?

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  • 2 months later...

I welded a chunk of stainless to the leg of my welding table. I clamp the ground there. If there is a ground problem, it is most likely in the connection,where the wire enters the clamp. sometimes you have to sand or grind the contact surface of the ground clamp itself. Also with high frequency it is best to ground the work itself.

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years ago when working on a construction project and the welder were a good distance away, we used to clamp a strip of inconel or monel to the building frame and position our ground clamps at varying distances from where the strip was connected to the building to vary our amperage at the stinger.

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