"Flush" welding

[v8bobber]

Hi all,

I have recently taken ownership of a Series one which needs a fair amount of work to be done to it until it is roadworthy again.

On previous vehicles I have welded patches onto the chassis and my welding is of a fairly good standard, however, on this occasion, I would like to be able to "flush" weld new metal into the chassis in order to leave an invisible repair.

I had it in my mind that I could make an accurate template of the area that needed plating and simply seam weld aaround it but I was told yesterday that I should possibly by "joddling" or "joggling" round the edges. However, from all the ones that I have seen, the will only deal up to metal that is up to 1.2mm thick which is obviously far less than Land Rover chassis thickness.

Is anyone well versed in this type of repair? Was I correct in thinking that I can simply seam weld a plate in, or is there some other technique that I am not aware of?

Regards,

Dave

[errol209]

I would have thought that the easiest way would be to cut the hole out to good metal, "puddle" a strip to the "good" and then offer up a slightly undersize patch into the hole. Should sit flush and much stronger and easier than a but weld.

(Puddle welding is cutting smallish holes back from the edge and then welding to the sheet behind around the hole edge - very strong.)

[integerspin]

(Puddle welding is cutting smallish holes back from the edge and then welding to the sheet behind around the hole edge - very strong.)

I cut the old metal away, then cut a patch slightly smaller and seam weld it in. If I

could be bothered to scurf the weld away you wouldn't be able to see it.

[longlandy]

beware of distortion and creating stress in the metal measure before during and after , remember weld can curl up 12mm plate

[LandyManLuke]

Any chassis repairs I do are flush. Cut out the rusty metal to a reasonably uniform shape, straight edges at least, to make cutting a well-fitting new piece easier.

I usually then use cardboard to make a template. It's quick and easy to work with a pair of scissors and a marker pen, and if it all goes wrong its easy to start again.

Once the new piece is cut out in steel, I use a flap disk to clean back to clean metal on both sides, about 10-15mm back from the edge, to reduce contamination. I also do the same on the chassis - if you find more holes at this stage you haven't cut back far enough!

It's worth tacking a bit of scrap to the repair piece, to use as a handle. Otherwise, every time you try to line the new bit up in the hole, it'll fall in to the chassis and you'll have to fish it out again.

I also usually chamfer the edges of both the chassis and the plate, as otherwise grinding it back flush will remove a lot of the weld, if penetration is not 100% this will leave a weaker joint.

[Ratty43]

You can reduce the risk of distortion by letting in round sections, but I doubt you're likely going to have any real problems on a chassis. I doubt you would be able to joggle steel of that thickness, I use one on classic car bodywork and it's hard going even on light steel. Errol209s' idea would be the easiest way although you can hold it flush by hand as long as you don't have the shakes.

[andyb]

I use on of those magnetic pick-up tools to hold the patch in place while I tack it into place.

[landrover598]

Cut out the rusty metal to a reasonably uniform shape, straight edges at least, to make cutting a well-fitting new piece easier.

Or an another way, which is how i do rust repairs, Cut the repair patch first, for a small rusty hole, say 3" x 3" square, then scribe around it onto the chassis and cut the chassis, if you follow the line then the patch will fit perfectly, fit flush held with two welders magnets, tack the 4 corners and then seam weld all around. simples

[Night Train]

I would always use a backing strip behind the joint.

Not only does it stop the piece falling in but it allows a decent weld penetration as it will weld all three bits together.

Just butt jointing, even with chamfered edges can lead to a weak joint, when ground back flush, as there is no guarentee that there is full and complere penetration all the way around.

Also the HAZ (heat affected zone) in and around the weld will change the properties of the base metal and that can lead to further weakness due to the weld being a bit more brittle and a little less tough. that is why usually a bead is left to make up for that weakness.

Anyway, this is what I was taught at welding college.

[Turbocharger]

Dave Lang's method works for me - but I've also found it's an excellent way to build up a stock of progressively larger patches, as you realise the rust is worse than you first thought...

[mickeyw]

I've always used the same methods as Luke, combined with the welder's magnets.