Wasn't quite sure whether this should go in here or in the bodyshop bit, but as its a bit more than painting or styling, I guessed in here would be better...


Anyway, I am going to need to do a couple of patches on my car for the next MoT, it has rotted slightly where the floor-pan meets the sill at the front of the car, on both sides.

One side will need a patch about 5" x 7", and the other side about 5" x 3", roughly.

So, what thickness steel sheet would I need, and as the bulk of the rot is where the floor-pan/sill join is, how far should I put the plate over the sill?

Cheers.

heh my car has parts of my computer case welded into it.

it deppends on what kind of welder you have really.. if you have a mig welder (one that feeds a spool of wire) you can set them quite low and weld thin stuff.
if you have a stick welder you want to use thicker stuff as a thicker steel plate will act as a heat sink and hopefully stop any holes being blown into the sill.

if you are welding real thin stuff you want to use as little amps (power) as possable as you just blow holes in everything.

take one from me, if you can find old computer case pannels they weld in cars a treat.

oh and always bitcho/paint the welded plate you have just put.. in stops it rusing.

when welding a hole in a car the way i always did it was scrape away the underseal untill you get bare shiny metal then cut a plate to size with a pair of tin snips and weld it in.
so long as the rust is coverd by the welded in plate it should be strong enough

hope this helps you out

I'll be using a MIG welder, one of the half-decent hobby ones.

I have a couple of old filing cabinets (steel) that are going for scrap, so I'm guessing I could cut some patches out of them?

I was planning to get one of those wire-brushes that fit on 4" angle grinders, and give it a good going-over with that prior to welding.

Ideally, you replace the metal with metal of the same thickness. Do not plate unless you want to do the same job again within a couple of years -- all the rust should be cut out.

OK, you can use "pre - used" steel, some welds well, some abismally. But for the hastle and expense, it's easier to pick up new offcuts from eBay or your local metal merchant.

The MOT is fairly specific on what kind of weld should be used -- use plug welds to replace spot welds, metal introduced in a part panel should be seam welded.

It would be welded as a seam, not spot.

I have no intention to just clean up the edges to enable the weld to stick, I would be removing the rust. I would be welding a patch over the (cleaned-up) hole.

Realistically speaking, I am likely to only keep the car for a couple more years. Don't read this the wrong way; I believe that if a job is worth doing, it is worth doing properly, but I am not willing to pump a never-ending amount of money into the car. I've already spent too much.

I was originally asking for what thickness steel I need, so I can order some off eBay, but if I already own suitable metal, I might as well try with that first.

Give it a go with a couple of bits of the "new" steel off the car. If it welds well, no problem.