making new arms for my spotwelder

[rally]

Hi all

I want to make some new arms for my spotwelder,
its one of the big heavy transforner ones that have 2 arms,
its portable for doing automotive panels etc

Eastwood, etc sells a similiar one

Anyway I need to spotweld a floorpan into place,
the arms that came with the spotwelder do not reach around the door sill so I can get to both sides.

What do I make the arms out of ?
do I need to drill+tap the ends for removable tips ?
do I need to insulate the arms sio they do not short out on the rocker / door sill ?

thanks for your ideas
Rally

[simono]

i have a portable spot welder and which different styles and lengths of arms are readily available, some might fit your machine and needs.
I suppose you could make special shapes if the ones you want were not available.
I'm guessing my arms are made from copper and the ends have oblonged holes for the electrodes and the wedge that keeps them in place.
If you were to make them they should be the right profile, so no need to insulate, or lay some insulating material over the points that may make contact with the arms.
I could supply some pictures of the ends of my arms if you would like to see how the electrodes are held in place.

[dauer]

Hi Rally;

I really don't have much experience with the small portable spot welders but in all my training in autobody, car manufacturers and repair organizations do not recommend them as they cannot generate enough tip pressure and current to make a strong enough weld. The shop I formally worked at has a spot welder which is huge and uses a air powered ram that generates several tons of clamping pressure to produce it's welds and some organizations still will not accept it as a suitable replacement for factory spot welds. The currently accepted method for welding in replacement panels is plug welding with a mig. making deeper and wider arms for your welder is going to induce a lot more flex and reduce the clamping pressure even more, I'd hate to see you go through all that work to find yourself with unsatisfactory or unsafe condition. Best of luck...


Dave

[Hemirambler]

Hi Rally,
I've made custom arms for my spot welder before - nothing elaborate it was just that the factory arms were so darned expensive!!! I used solid copper bar stock and bent it using my hydraulic press - solid copper bends very nice around a small radius.

I opted for replaceable tips - made from the same bar stock, but in reality you don't need them. Matter of fact that is the first place you need to check if you're getting bad welds. they tend to oxidize (not sure if that's the right term) and ultimately reduces the effectiveness of the unit. Making the tips "built in" would eliminate that problem. Besides you could ALWAYS add replaceable tips later if you wore the integral ones out.

My spot welder worked 100 times better with good clean tips and good contact between the tip and arm. :lol:

FWIW I think buying the copper was about 1/3 to 1/2 as expensive at the time than purchasing the arms. I've also "reclaimed" old arms by cutting the ends off and rebending them.

Keeping the metal CLEAN is paramount to getting good results -if that's not possible then I too would vote for the plug welds - done right they'll be near invisible.

your mileage may vary



Jacin in Ohio

[custommetal]

Rally, the other posts are correct. not enough pressure or dirty tips and especially sheetmetal where it overlaps will cause problems. the other thing to consider is if the car is a unibody construction. Here the floor pan is an integeral part of the car structure and support. If the welds are poor body flex can be a problem for the doors, fenders, seats etc. I have found it easier to just punch a hole in the top panel every 3-4 inches and plug weld. remember to seam seal the joint after welding on both sides to prevent water entry. good luck and keep a fire estinguisher handy.
George

[custommetal]

Rally, the other posts are correct. not enough pressure or dirty tips and especially the sheetmetal where it overlaps will cause problems. the other thing to consider is if the car is a unibody construction. Here the floor pan is an integeral part of the car structure and support. If the welds are poor body flex can be a problem for the doors, fenders, seats etc. I have found it easier to just punch a hole in the top panel every 3-4 inches and plug weld. remember to seam seal the joint after welding on both sides to prevent water entry. good luck and keep a fire estinguisher handy.
George

[Gene_Olson]

good luck and keep a fire estinguisher handy.
George

It is worth the trouble to have a couple CO2 extiguishers around. (2 so you can rotate one to have it refilled when needed)
They are great for putting out fires and cooling stuff quickly.

If you want to ruin your day, spray something with a powder extiguisher. It will put out the fire but it will make a huge mess.

The key to fire suppresion is early detection and action. If you are working around finished stuff the CO2 is great, cause it puts out small fires or smoldering stuff (like a weld spatter that bounced wrong) NOW and leaves no residue. It can mean the difference between spot cleaning something and total replacement.

Having the ABC rated extiguisher around is good, in fact my insurance specifies it MUST be in my shop next to each exit door. Having a BC rated CO2 extiguisher where you can reach it makes even more sense.

It can also be used for cooling when heat shrinking where you don't want to get something wet. (though obviously water is a lot cheaper and therefore preferable)

G.