120 welding info

(Rick Hughes) #1

I’m toying with the idea of buying a 120 project. I understand the bonnet was aluminum. Are any other panels or frame made out of a material that isnt steel? I’m comfortable mig welding steel, but I have no experience with other types of materials. Thanks in advance.


(CP120) #2


The doors and boot (trunk) lids are also aluminum on OTSs, DHCs and FHCs.



(Rick Hughes) #3

Thanks Chris. I suppose I could try to learn a new skill🤔. Does anyone know if you can weld aluminum with a mig welder?


(Ed Nantes) #4

I think TIG is the way to go. Or oxy if you are very old school

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(Christopher Potempa) #5

Plus 1 on the TIG. You’d be welding pretty thin wall stuff and unless going with TIG, there would be a lot of burn-through. Both Lincoln and Miller make a good, thin wall aluminum capable TIG welder that’s very portable but start at around ~ $1400 or so base price. Far, far lighter in weight than the older transformer type welders as these use electronic inverters to make the sine wave. Of course, if they fail then it makes for a pricey repair. Factor in a regulator, gas bottle (or two, for a spare) plus replacement tips. I’m a tool guy and itching to purchase one myself, but if all I have to use it on are some stress cracks on the bonnet plus same on the drivers side door hinge area, then it becomes hard to justify. Best to take what you have then to a professional welder. Also, do not cave in to buying one of those cheap imports from Harbor Freight and the like. That’s just throwing money away on unsupported import junk.


(restorer32) #6

Tig welding old usually corroded aluminum is a far cry from welding new clean aluminum.


(Roger King) #7

I have both MIG and TIG. I don’t believe it is possible to MIG weld aluminium - I’d suggest asking on a specialist welding website. I use the TIG for both steel (DC) and aluminium (AC), but mostly for fabrication as I don’t use filler rod. TIG welding old metal, especially aluminium, is not easy. I use Argon/CO2 mix for MIG welding, pure Argon for TIG. You can use the Ar/CO2 mix for TIG but it’s not as clean.

Now I just need to perfect my timber welding skills for the doors and bootlid of my 140.


(Rob Reilly) #8

Aluminum can be MIG welded, usually done in high production jobs like outdoor furniture, but I have done a bit of it on XK120 work. But for low production and one-off jobs at my Lab the welders always did TIG. On thin sheet you want a backing piece like copper or ceramic to stop burning through.
For years I struggled with what I’ll politely call an “entry level” MIG welder called UnoMig made in Italy, as it was all I could afford to get into MIG welding. Last year I bought a Vulcan OmniPro 220 which does MIG, TIG and stick, and I couldn’t be happier with it. Its every bit as good as Lincoln or Miller.


(Jim XK140 FHC) #9

I have used mig / argon on aluminium. It welded nicely but I was working on maybe 3mm plate . Never tried thin stuff


(Roger King) #10

As Rob says, good quality kit is essential. ‘Hobby’ equipment is generally much, much harder to get good results with. I have a nice UK-made Portamig and a R-tech AC/DC TIG welder, so much better than the kit I had before. It reminds me of trombone-teaching days - I’ve had students given cheap brand-new Chinese instruments I couldn’t get a half-decent note out of, whereas a 10-yr-old well-used American 'bone costs the same but sings like a bird.

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(Mike Spoelker) #11

If you do not have extensive experience with TIG welding old, thin aluminum, you will want to hire that task out to an experienced professional. Aluminum does not weld at all like steel. Because aluminum is such a good conductor, It takes a much higher amperage than would steel of a similar thickness. And all that heat makes it very easy to warp the panel. In contrast to steel, it also exhibits virtually no color change as you heat it, so it is difficult to tell when you might be getting ready to blow a hole in the work. And any kind of corrosion in the weld area makes it all the more difficult.


(Paul Wigton) #12

Could not agree more: repairing thin, old body panels is NOT where one wants to begin TIGing aluminum.


(Mike Spoelker) #13

That is pretty good advice. If you are going to learn a new skill, gas welding thin aluminum is a good one to have. I still would not start the bottom of the learning curve standing in front of a XK bonnet or boot lid, torch in hand.


(Nick Saltarelli) #14

You can weld aluminum with a MIG spoolgun and argon but on material not much thinner than 1/8”. I’ve had little difficulty (Lincoln 220 Square Wave) TIG welding the old aluminum of my XK120 bonnet where it (and just about all of them) cracked but it requires perfect cleaning. It also doesn’t hurt to preheat the area around the repair area beforehand using propane, reclean with a stainless brush and fire away. Nowhere near as easy as TIG welding steel. Practice, practice, practice on some 18 ga scrap before tackling your bonnet, doors and bootlid.

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(Roger King) #15

A few old Land Rover panels are great to practice on. Same age, and given the locality both vehicles were built in, quite possibly the same material (although LR used the Birmabrite process).


(Ed Nantes) #16

A few years ago , I worked at a specialised Aviation welding place for a few days. Not doing anything clever, They were welding a chassis together for me and said if I did the basic work , they’d do the actual welding and I’d save $$ and get exactly what I wanted. At lunch we talked about welding Jag heads and water manifolds,as he had one there someone had dropped in to be repaired.
The basic issue is that aluminiums are different [ let alone aluminums] , for different charcteristics. One can’t melt don’t coke cans and make S Type front wishbones.for example.
So heads are made of an alloy that amongst others things, is resistance to corrosion. So it’s a bit pointless welding up corrosion with TIG rods made for making treadplate toolboxes.
Of course you can buy the correct TIG rods.
BUT… there’s a minimum order. We checked up. Yes the suppliers had it, minimum order 100…
As the welder said. I’ll never use that many…

So perhaps a company specialising i n alloy head repairs might use it… or not. Then there’s heat treating afterwards.


(Nick Saltarelli) #17

Ah, yes. Quite right. I would have to look up the particular alloy filler rod I used for repairing the XK120 aluminum (aka in some parts of the world aluminium) but it does make a difference. We can buy 1 pound tubes of the different alloys here. Not expensive.


(restorer32) #18

We used to have spaces at the Carlisle Swap Meet. Next door to us was a fellow selling “Miracle” aluminum welding rods. After watching him for several hours I realized what he was doing. To demonstrate his products ability to weld thin aluminum he would weld two Coke cans together. To demonstrate its effectiveness on corroded aluminum he would weld an old aluminum head. Never did he weld thin corroded aluminum. I became friends with the fellow and he told me how he was able to do the amazing welding he did. Turned out he had been a welding instructor for 27 years.


(Nick Saltarelli) #19

I can’t count how many times I’ve been to Spring Carlisle. 30 maybe. You never know what to expect weather wise. One year there was a heavy dump of wet snow and the following year it was blisteringly hot.

I’ve used the miracle aluminum rod successfully many times and still have a tube of it. It’s not welding but the equivalent of brazing. You get the aluminum really clean using a stainless steel brush then heat it up with a propane torch to the point the rod melts onto the aluminum. Then you use a thin SS rod flattened and sharpened at the end to scrape the aluminum under the puddle, which lifts the Al2O3 off the surface and allows the rod material to bond. It actually works well though it has limitations true TIG or OA welding don’t. The join is strong but hard. Brittle even. Any bending or hammer/dolly work after ward will cause the repair to crack. It also contaminates the aluminum making it impossible to follow up a difficult repair that hasn’t gone especially well (as happens sometimes) by welding. The stuff has its place but using it for bodywork is tricky.


(Gazzam) #20

Hi Nick,
Have you had a chance to identify that filler rod?
I welded a small piece using a general purpose ally rod and it seemed to work but it cracked right along the weld when it cooled.