Author Topic: Spot welding.  (Read 17317 times)

Bob Purton

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Spot welding.
« on: December 26, 2014, 05:09:23 pm »
Hi fellow restorers.
Spot welding, just about the only kind of welding I havnt tried before.
Over the holiday I have been building my Bobette windscreen frame from 1mm sheet steel, its gone very well so far but I now need to weld some members to the inside of it to stiffen it all up, all that's giving it its shape right now is the windscreen its self temporarily mounted in it and the sides which I have folded.
I want to bend and weld some square rods to the inside of the curves, top and bottom, can this be done with a spot welder or are they only for sheet to sheet?
Second question, I dont want to lay out £500 to just do this job, is there a kind rumster out there with such a device that would be prepared to loan it me please?  Hire shops around my way dont appear to hire them out for some reason. I know I could do plugs welds with my mig but want to keep and refinishing to a minimum.  Any ideas anyone?

messyman

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Re: Spot welding.
« Reply #1 on: December 26, 2014, 05:23:18 pm »
ive got a spot welder but I no you can do it with a mig and some holes cut into steel ,my spot welder I think only dose upto 4mm.... I don't no where u r but mine is available if needed
messyman restorator of rust relics vw or bubblecars
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Bob Purton

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Re: Spot welding.
« Reply #2 on: December 26, 2014, 06:05:26 pm »
Thanks. I just finished having a chat with a professional welder chum and he is of the opinion that I would do a lot of damage trying to weld sheet onto 8mm square rod which was the original plan. Distortion and maybe blowing the sheet out altogether. He said the only way to do this with spot welding would be to weld the sheet to channel but then bending the channel to the frame profile would be a headache for me as I dont have the right tooling for that.
He suggested riveting of using one of the modern high tech bonding products now available. I see I am going to have to think this trough some more.
Thanks for the offer, I'm down in Essex though so distance alone would be a problem. Good to know forum members are willing to help.

Peel replica, Steve Fisk

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Re: Spot welding.
« Reply #3 on: December 26, 2014, 07:45:27 pm »
Can we have some pictures please Bob

messyman

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Re: Spot welding.
« Reply #4 on: December 26, 2014, 08:29:34 pm »
Essex ant far really lol Cambridge - peterbough - spalding / wisbech
messyman restorator of rust relics vw or bubblecars
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Bob Purton

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Re: Spot welding.
« Reply #5 on: December 26, 2014, 08:50:20 pm »
Steve. Have sent you an email.

Messy. No I suppose its not that far 100 miles or so but now I'm doubting that spot welding is the answer.  Cheers.

messyman

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Re: Spot welding.
« Reply #6 on: December 26, 2014, 08:53:30 pm »
well the offer of using tooling or workshop is here if u need
messyman restorator of rust relics vw or bubblecars
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Bob Purton

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Re: Spot welding.
« Reply #7 on: December 26, 2014, 08:59:25 pm »
Very kind of you. I may still take up the offer.    Cheers, Bob

Mark Green

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Re: Spot welding.
« Reply #8 on: December 26, 2014, 10:56:47 pm »
How about drilling a small hole and using silver solder with very low heat?
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Bob Purton

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Re: Spot welding.
« Reply #9 on: December 26, 2014, 11:06:05 pm »
Hi Mark. This may be a case of being divided by a common language here as silver solder in the UK means the metal has to be red hot. As soon as you apply that kind of heat the sheet metal warps. Do you mean soft solder?

Mark Green

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Re: Spot welding.
« Reply #10 on: December 26, 2014, 11:19:12 pm »
Yes silver solder is the same here. I just the other day silver soldered some studs to 1 mm steel and it did not warp on me. Maybe I was very lucky!
« Last Edit: December 26, 2014, 11:51:19 pm by Mark Green »
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AndyL

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Re: Spot welding.
« Reply #11 on: December 26, 2014, 11:43:42 pm »
Stay Brite silver solder is low melting point.
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Bob Purton

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Re: Spot welding.
« Reply #12 on: December 27, 2014, 08:37:53 am »
Maybe your just better at it then I am Mark!

Bob Purton

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Re: Spot welding.
« Reply #13 on: December 27, 2014, 08:51:37 am »
Hmmm Stay brite doesnt appear to be sold over here. I wonder if there is an alternative brand with low melting point.

Andy, you appear to be clued up on modern adhesives, what's the best panel bond?

The other thing that crosses my mind are countersunk stainless pop rivets. anyone used them?

Big Al

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Re: Spot welding.
« Reply #14 on: December 27, 2014, 09:14:09 am »
I thought one reason for using spot welds was it deformed the sheet metal less.

Having watched Mick do it he used some rivets to get the fit correct, or the threaded thumb clamps, forget what they are called, if they will go in. With the thing located he would then weld in a way rather like tightening a cylinder head. This spread the loading along the seam. Once the spots were holding the job the rivets/clamps came off and the job was finished off, lastly filling in the original clamp/rivet holes.

Of course proper spot welders are a clamp as well. that is a problem when you cannot access one side of the weld, or the electrode energy is dispersed by being away from close proximity to the the other, on miss matched metal thickness. it can turn into a zipper, a known prob on Schmitt monocoques.

Interestingly the normal screen surround I have found on low production cars is a channel with rivets, not least as the channel is sometimes brass extrusion. It is more malleable and chrome's up nicely. Even tin bodywork is riveted onto brackets hidden under the surface. I actually have a box of Misc rivets for repairing such things. Though cheaper cars can have a panel with a hole cut in and the screen rubber mounted. This rarely looks well.
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