Spot Welding technique...

[jrcflash]

I have the floor platform and pans cut out and support rails prepared for welding in new metal. I am unsure of how to perform the actual spot welds to attach the pans and platform. Should I screw through both the new pans and the rail and then remove one screw at a time and weld up the hole? If so what size screws should I use? Or should I drill holes in the new metal only without going through the support rails? My welder is a Miller 211.

 

[bmc69]

You can (and I do) screw or riv-clamp everything together and weld those holes closed later, but those are NOT the ones I use to actually "spot weld" the stuff together. The actual structural welds are done as you suggest in your second question; holes in the new metal only. I use 1/4" holes myself...others may differ.

 

[thegreatjustino]

Sheet metal screws every couple of inches holding both panels together. Holes in between the sheet metal screws on the upper panel only. Weld the holes between the screws to attach the pans. Remove the sheet metal screws and weld those holes shut.

 

[bmc69]

Sheet metal screws every couple of inches holding both panels together. Holes in between the sheet metal screws on the upper panel only. Weld the holes between the screws to attach the pans. Remove the sheet metal screws and weld those holes shut.

What I said...er...what he said. ;D

 

[hankjr]

Harbor freight has a nice little pinch and flanger that's air powered and makes quick work of it.

 

[hankjr]

Punch and flanger. Catch it on sale or with 20% of coupon for around $35.

 

[Broncobowsher]

plug weld is what you will probably be doing to replace spot welds. Hole drilled/punched in the upper layer of sheetmetal, ¼" or so. Then fill the hole with weld with your wire feed welder.

If you use screws or clicos you weld those holes shut after the plug welds.

To really spot weld you need a spot welder and a big collection of jaws to reach all the spots.

 

[deltarat]

Harbor freight has a nice little pinch and flanger that's air powered and makes quick work of it.

I bought one of them and it was the most time saving tool that I have bought.

 

[hammer189]

looked at Harbor Freight for pinch and flanger but didn't find anything. Anyone got a part number? I'm gonna have to start welding one of these days.
Thanks, David

 

[bmc69]

I bought one of them and it was the most time saving tool that I have bought.

The only "issue" I have with mine is that the holes it punches are smaller than what I like to use for my plug welds.

 

[hankjr]

looked at Harbor Freight for pinch and flanger but didn't find anything. Anyone got a part number? I'm gonna have to start welding one of these days.
Thanks, David

Central pneumatic #1110 is what mr google says

 

[sp71eb]

Most vehicle manufactures recommend a 8mm or 5/16 plug on most body panels with welds spaced 1 1/2" apart. I often use 1/4" plug welds, but I will say if you do you need to be a competent welder. If you don't get the base metal hot with a 1/4" hole you will just pile weld on top of it and fill the hole without welding the two pieces of metal. The best way I have found to weld plug welds starting in the center of the hole hit the trigger and make one circle around the hole. The welder needs to be a little hot so you can get penetration into the base metal. A good spot weld should not be tall and should take minimal grinding to dress. The air punches work good but they only let you punch the hole close to the edge of the sheet metal. I like the dentfix hand hole punch.

http://www.autobodytoolmart.com/dentfix-14-hole-punch-pliers-df-8-p-11748.aspx

http://www.harborfreight.com/air-punch-flange-tool-1110.html

 

[Broncitis]

I use a HF punch/flanger for most all of my plug welds. They seem to work fine.

I also have a HF spot welder that after a few years of owning, I finally used a couple months ago on a rocker panel and kick panel repair. It worked great overall! Super clean with almost no need to go black with a flap wheel to blend the plug welds. It looks to be a near identical copy of a Miller spot welder that was given to me since which is mounted to a Miller base with a foot pedal (for off vehicle work).

I would think 1/4" on thin sheet might be the most I would want to go since that is going to take more puddle and heat to fill in than the smaller holes which seem to work pretty well for me. I too start in the center and make one pass around to fill the hole. On sheetmetal, I prefer .023 wire, but it does have more of a tendency to be more finicky to feed roll tension and will bird nest in the feeder if it is not just right and your lead to the gun is not fairly straight or has gentle turns in it. .030 usually works OK for me as well, but I like how I can weld to thinner base metal that has lost some metal due to corrosion that has been cleaned away in the cases where you can not cut out all the way back to 100% solid metal (often in flanges or seams were new panels attach). The .030 will often want to blow through even on low settings where the .023 will not.

This is all based on my Miller 210 with gas.

There is another type of spot welder that uses two independent hand held electrodes. I forget the name of it and I could not locate it with a quick Google search by the terms I used. My dad's buddy has one, but I have not personally tried it yet.

I think it is this one: http://www.handsontools.com/Lenco-L4000-LENCOSPOT-MARKII-Autobody-Dual-Spot-Welder_p_1095.html

There are also some other cheaper spot weld or pseudo-spot weld guns from Eastwood that are operated single sided do you do not have to have some of the crazy shaped tongs or for places were the back is not even accessible by tongs or a hand held electrode.

 

[Steve83]

Body panel adhesive is stronger than welding, and doesn't cause corrosion, or even risk weakening the old metal. It also seals the seam as it bonds.

 

[hammer189]

Thanks for the info guys!
David

 

[bmc69]

On sheetmetal, I prefer .023 wire, but it does have more of a tendency to be more finicky to feed roll tension and will bird nest in the feeder if it is not just right and your lead to the gun is not fairly straight or has gentle turns in it. .

*snort*...four times yesterday. Four times! %) I still need to clean up all the strands of wasted .023 wire laying around the shop floor.