How to fasten electrodes on a spot welder ???

[ksor]

I need some advice on how to connect/fasten an electrode to the jaw on my spot welder 

You can choose language for translation in the upper right corner !

Look here and ... yeah, come up with some good ideas 

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

[awemawson]

Well viewing with the 'English' option set certainly displays in a language I don't regcognize as that spoken by our dear Queen!!!!!

The electrode tips in my spot welder are retained by tapered cotter pins (*)  into the electrode arms- you set the position then tap them lightly with a hammer. The electrode arms are retained by a split clamp arrangement tightened using a hex allen key.

(*) Cotter pins - the English meaning like those that retain the pedal crank on a bicycle to the bottom bracket shaft not the American version that we call a split pin. ie a cylinder with a slice removed at an angle to the axis to form a cylindrical wedge, retained in the case of a bicycle by a nut on a threaded extension, and in the case of a spot welder by a whack with a hammer !!!!!

[ksor]

Well viewing with the 'English' option set certainly displays in a language I don't regcognize as that spoken by our dear Queen!!!!!

The electrode tips in my spot welder are retained by tapered cotter pins (*)  into the electrode arms- you set the position then tap them lightly with a hammer. The electrode arms are retained by a split clamp arrangement tightened using a hex allen key.

(*) Cotter pins - the English meaning like those that retain the pedal crank on a bicycle to the bottom bracket shaft not the American version that we call a split pin. ie a cylinder with a slice removed at an angle to the axis to form a cylindrical wedge, retained in the case of a bicycle by a nut on a threaded extension, and in the case of a spot welder by a whack with a hammer !!!!!

The translation ... argh, Google has to better on that issue - you'r just right, but I'm sure an english man understand this Google-english better than the original danish - right !

Any arrangement going AROUND the electrode will of couse take up space - and that's not adviseable concerning the FIXED jaw - it should be as small as posible - could the 8 X 8mm elektrode be welded to the end of the 30 X 8 mm jaw ?

But the welding method can not be used for fastening the electrode to the moveable jaw    but normaly here will be more space for an arrangement like ours ... yeah maybe 
 

[buffalow bill]

Ksor,
How about making the two arms from steel, provided they are insulated from each other at the machine end. The two electrodes, bolt to the arms, then use welding cable for the electrickery bit. This will give you the flexibility at the upper arm. If the transformer is suitable the welding cable may be threaded around the tf core thus eliminating connections at the transformed. To terminate at the welding tips use brass bolts to secure the cable lugs. This depends upon the size of transformer and welding current.
Depending upon what you are welding, it is possible to anneal the weld. Keep pressure on the welded parts, add a delay then activate the welding transformer but at a lower setting.
Hope this helps. 
Bill

PS If welding cable is a problem, it is better to use lots of small section copper rather than one large section. High density current will flow along the outside of the conductor.

[ksor]

Ksor,
How about making the two arms from steel, provided they are insulated from each other at the machine end. The two electrodes, bolt to the arms, then use welding cable for the electrickery bit. This will give you the flexibility at the upper arm. If the transformer is suitable the welding cable may be threaded around the tf core thus eliminating connections at the transformed. To terminate at the welding tips use brass bolts to secure the cable lugs. This depends upon the size of transformer and welding current.
Depending upon what you are welding, it is possible to anneal the weld. Keep pressure on the welded parts, add a delay then activate the welding transformer but at a lower setting.
Hope this helps. 
Bill

PS If welding cable is a problem, it is better to use lots of small section copper rather than one large section. High density current will flow along the outside of the conductor.

8
I think the arms should be made of cobber or aluminum - but I HAVE some cobber rods 30 X 8 mm !

What worries me is the the lack of contact in my collections bolted with bolts of steel - I think it CAN be a problem at high current flow = 2-400 Amps - but I have to make the surfaces as smooth as posible and high tension on the bolts too.

I think I have the right solutions now and I have updated my drawings.

[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