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How to fasten electrodes on a spot welder ???

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andyf:
Ksor, it is true that copper offers only about 1/10 the resistance of carbon steel, and aluminium about 1/6, but I don't think you will see any substantial voltage drop along those short and fairly thick arms.

If you are still worried, you could simply attach the cables direct to the electrodes themselves, so the arms don't carry any current. It would not look as neat, of course.

Andy

John Hill:
My old spot welder has copper arms which get quite hot, far too hot to touch, after just one weld so obviously there is a lot of energy being wasted there.

The end of the arms have conical sockets into which the tips are fitted,  previous owners used their biggest hammers to do this!

Lew_Merrick_PE:
Guys, using steel as an electrode pretty much assures that the electrode will end up being welded to the (steel) part.  This is why arc-welder clamps are copper plated.  The issue is (if you will) alloy compatibility.  Think about it.

Now, as to attaching the electrodes for a spot welder, you really have to make one of two choices: (1) Does your power cable connect directly to the electrode or (2) Does your power cable connect indirectly to your electrode?  If the power cable(s) attach directly to the electrode, then you need concern yourself only with the mechanical aspects of the electrode.  If your power cable(s) attach indirectly to the electrode then you also need to consider the full contact area for electrical power transfer as well.

Industrial/commercial spot welders tend to allow the electrode to sit in a clamping collet type of affair with a fairly large contact area and provide power cable connection somewhere else.  I admit I have not really thought this through, but somebody (almost certainly) has and the general answer is what we see in industrial/commercial spot welders.  Unless you know of a reason as to why this is the wrong answer, I would use industrial/commercial experience as a guide.

DISCLAIMER:  I doubt I have made more than 750 spotwelds in my life.  If somebody with (say) 500,000 spotwelds of experience wishes to argue with me on the subject, I will readily cede to more experience-based knowledge.  What I have made here is an observation.  I admit I do not have enough experience to justify holding an opinion.

ksor:
Now I got a little further with the spotwelder:

http://kelds.weebly.com/punktsvejser.html
  :coffee:

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