Plug Welding thick to thin

[anjer]

I'm fixing the floor pans in a 2cv. The replacements would be thin steel (0.8mm) and will rot out again in no time.

Therefore, I am going to have a go at making my own using 1.2mm or even 1.6mm since they are basically flat panels.. Using box section for the strengtheners underneath. For plug welding the thicker steel (i.e holes drilled in the thicker steel) to the edge of the sills etc do i follow the tutorial or is there a different technique. Hope this makes sense.-I've bought a Portamig 185 .

 

[fingers99]

I'd stick to the original thickness. Should last a fair while given decent quality steel and good primers etc. Really you want to plug so that the thinner layer has the hole in it.

 

[chooowie]

DON'T GO OVER 0,8 !!!!!

When you take a look at old panels, you probably don't have left more than 0,3 mm of healthy material( when you remove rust and all other sh!+ which IS NOT healthy metal). If you can, try finding 0,5 - 0,6 sheet, it's much easier for modeling and much easier to fuse it together with old parts. If you make floor panels too strong in opposite to paper-like leftovers of original metal, you will have cracks all over your car before you can imagine it.
As fingers said, don't even try plugging it with hole on thicker layer, that way you can only produce another hole on thinner one( when you try to plug it).
If using box section for strength, again, try finding thinner material and don't make it too strong, rather use profiles that you will model out of thin sheet.

 

[malcolm]

The 2CV floor is a large double skinned flat section. It's reasonably common for reproduction chassis to use slightly thicker section, so in this case cracking shouldn't be a trouble.

Personally I go 1.0mm from 0.8mm on the R4 chassis, and certainly wouldn't go thicker than 1.2mm. It will get heavy and much more difficult to work and attach.

For plug welding I agree it's easier to weld through the thinner sheet - otherwise it will be easy to burn holes in the thin sheet once the power is increased to melt to the thick stuff. If you need to have holes in the thick section try welding from the outside of the hole inwards rather than the normal inside out. Try a few practice pieces first to work out the hole size and technique. Test them by pulling them apart in a vice to make sure you have a good join to the other sheet.