Stubborn Floorpan

[mjhco6]

I'm in the process of replacing the floorpan in my ranger. Ive cut the old mess out and currently installing the new pan. Some areas are welding well and others.. not so much. I've tried just tacking, then I tried plug welding with screws.. Everytime the 2 metals end up separating. There's only a couple times I will be able to break off the old caked on welds and try again. I'm using a Hobart Auto Arc 100 Mig welder (w/o gas) and .030 flux cored wire. Settings are on 1/25.. Sheet metal is only about 20-22 gauge. Any suggestions would be appreciated. Thanks.

 

[rikrobson]

No gas isn't the best for auto work, but saying that its just sticking two bits of sheet steel together.
can you elaborate on setting 1/25
if you can get some 20 gauge steel to practice on to get the settings correct it would help. Eniugh power to penetrate, but not enough to blow through. also the joints need to be clean.

 

[keithski122]

When this happened to me when plug welding I drilled the holes a bit bigger, probably to 8mm.

 

[mjhco6]

1 (heat/power) 25(wire feed speed) Both pieces were hit with a wire wheel grinder. There are some spots that the cake welds won't come off, but for the most part it is clean the next time I try to weld.

 

[macandmoss]

Try invest in a hand flange tool for your floor pan , makes an easier job for amateurs like me ..lol ,and punches holes as well for tacking hold , get them for about £20 on eBay , Hope that helps

 

[pedrobedro]

Try invest in a hand flange tool for your floor pan , makes an easier job for amateurs like me ..lol ,and punches holes as well for tacking hold , get them for about £20 on eBay , Hope that helps

Joddler with hole punch, I fancy one of those myself but never got round to buying one. They've come down in price since I last looked

 

[grim_d]

I found 5mm far too small for plug welding, filled the hole before penetrating the steel underneath properly. As above I would generally drill an 8mm hole.

You don't find many 5mm spot weld drills...

 

[mjhco6]

I started over again last night.. I ran a 1" bead across the floorpan and existing truck floor metal. I've got atleast 100 welds across the floorpan. It's holding now. I bought some fiberglass/resin/hardener to run across the welds on the inside to seal them up. On the bottom of the truck I've got some butyl rubber I'm going to run in the tiny crack to seal it, then spray it with rubber in a can.

 

[chris y]

With a small machine you will need an 8mm hole as people have said and possibly all of the heat available.
You should practice on some scrap, practice arcing up on the back material in the centre of the hole then move out and in a circular motion.

With a small machine and a small hole and just a burst of weld the best you will achieve is something that is stuck on, not welded. It shouldnt be "holding" it should be a proper weld with penetration in every one.
All cars flex and if the welds are not penetrated they are going to break.

If you practice on some scrap you can try to separate the parts and see if its impossible and you just destroy the surrounding steel.