Advice and guidance on repair and restoration techniques.
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Repairing diecast, aluminium, pot metal and cast iron

Postby daveslot » Fri Jun 07, 2013 4:21 pm

Has anybody been successful repairing holes in aluminium castings, the type of repair which will be on show, i.e. in a polished section? Seen ally rods, non flux type on ebay and wondered if anybody had used 'em.

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Re: Repairing ally castings

Postby johnnyo57 » Sun Jun 09, 2013 9:14 pm

I had a crack in a Sega mad money front casting welded up using TIG method it worked very well, aluminium is not very easy, nigh on impossible to weld with any other method.
Holes can be filled but you will need to dress and polish it up afterwards obviously. I would suggest you find a company that can do this for you should not be expensive
as it would only take about 5 mins to do.

regards john

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Re: Repairing ally castings

Postby pennymachines » Sun Jun 09, 2013 9:40 pm

Having recently experimented with the fluxless aluminium "welding" rods, I'm inclined to agree with John. It's probably more sensible to hand it to a professional. I just repaired an internal aluminium casting using the rods, but it took quite a bit of practice on other bits first, and I don't feel ready to try it on my Bradley Challenger casting until my technique improves.

It's fun learning how to do it yourself, but not such fun if you ruin a vital part. I'll report back when I've tried a few more pieces.

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Re: Repairing ally castings

Postby JC » Mon Jun 10, 2013 12:18 am

Although not a 'welder', I have done a bit of welding in the past (although only on steel) but I do understand the science to a fair degree. Aluminium welding was traditionally very much a black art, to be performed only by a select few experienced welders, with a unique skill. Aluminium could only be welded with oxy-acetylene, using a sulphur-based flux. I recall hydrogen was often used as an alternative to acetylene, although I don't know for what reason. Aluminium welding was one of those skills that you could either do or not - and most couldn't.
In more recent times, TIG welding has become the norm, using tungsten wire and an argon gas shield (unlike steel, where more or less any inert gas will work - CO2 being the norm, aluminium needs argon).
TIG welders are expensive - really expensive! OK you can get cheaper TIG welders (although nowhere near as cheap as MIG welders), but a decent TIG rig will cost several thousand pounds. Now, I've heard a little about these 'aluminium rod' gimmicks, although I admit it is only a little. But I have to question whether they can be a serious alternative to ' doing it properly' - I would certainly question whether this method can offer any reliable strength. They may well be OK for 'patching up' but I am inclined to put them in the same league as spray 'chrome' paint.
My advice - if you want to weld aluminium, pay someone who knows what he's doing.

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Re: Repairing ally castings

Postby youngerap » Mon Jun 10, 2013 12:32 pm

JC wrote:My advice - if you want to weld aluminium, pay someone who knows what he's doing.
I tend to agree. In a past life my brother was a specialist aluminium welder for the USAF at Mildenhall, so I asked his advice on welding cast aluminium. His view was that it should be relatively easy with the repair being strong and invisible, but qualified this view with the assumption that the welder knows his stuff! Otherwise, it would be the easiest thing in the world to go from minor repair required to disaster in the matter of seconds. His advice is to do your homework to ensure that the guy you are commissioning is qualified to weld aluminium and can prove it.

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Re: Repairing ally castings

Postby pennymachines » Tue Jun 11, 2013 1:49 pm

Yes, that's the point, a specialist aluminium welder has countless hours experience. That's where the advertising of these fluxless rods is not 100% honest. You really can't just pick them up for the first time and expect success. It takes a bit of practice to get a feel, for example, of how to distribute the heat around the casting (without flux, you don't get much visual indication of temperature).

Before dismissing them as a gimmick, I thought it worth experimenting a bit. As I said, I've now successfully repaired a casting, but, like JC, my main concern was whether the joins have "any reliable strength". According to the advertising, it will produce a join stronger than the original material. This is how they describe the bonding:
... a grain boundary reaction takes place that causes Aluminium ions from the bodies being welded and Zinc, Copper and Manganese ions from the Techno-Weld to diffuse across the weld boundary to a depth of several microns, producing a genuine weld.
Whether this should really be called welding, brazing or soldering needn't concern us here. What matters is - will it make a clean, strong, long-lasting join?

Techno-Weld has been thoroughly evaluated by the Technical Welding Institute (TWI) and been recognised as "Opening the door to a revolution in the process of Aluminium joining technology" ... it has also been given full approval and support from the British Aluminium Plate Research Centre in Birmingham (I found nothing about such a body on the internet) ... endorsed by BOC LTD and Reynolds Metal Corporation (presumably Reynolds Metal Company - now merged with ALCOA) ... for use in welding Aluminium as a valuable alternative to conventional welding.
Techno-Weld - the Product

So much for the blurb. Here's how I tested it:
I sawed through a piece of flat aluminium stock, roughly 2.5cm wide and 2mm thick, ground and cleaned the edges with a spinning wire brush, then joined them together again using the rod.
I then ground flat and polished over the join.
Finally, I put the piece in a vice and walloped it with a rubber mallet to see if the join would break.

Here's a close-up, after bending. There was no opening or cracking along the join. I'm sure no glue would stand this test.
My conclusion is that this is a useful addition to the slot restorer's armoury, suited to the kind of repairs we tackle, particular when professional welding would be too expensive.
It would not do for safety critical items like bike frames, where the process would destroy the aluminium's heat treated strength.

The Technique
As I said, you will not get a good join until you master the technique. I used HTS-2000 rods (similar to a number of other brands) which came with some basic instructions.
My first efforts were not encouraging. I tried fixing a broken mazak pinball plunger surround (surplus to requirements), but the casting wanted to melt before the rod. Subsequently, I found there's a method of dealing with this, but it seems quite difficult to master.
For now, I'm working with aluminium castings. After initial frustration, I searched the internet for guidance and found these videos created by Technoweld, which convey what you have to do much better than written instructions.

1. Grind the edges to be joined to clean metal, then clean with a stainless steel brush reserved for the purpose. This removes the oxide layer which quickly forms on the surface and would be a barrier to joining.
2. Apply heat. Butane/Propane is fine for weights up to 1/4". On my first attempts, in order to avoid melting the castings, I used a fine tipped butane/propane torch, but soon discovered a broader heat source was needed. It is essential to spread the heat around the piece, not just at the join.
3. Rub the rod along the edge. When the temperature is something above 380°C, it will melt and you run a bead of it along the edge.
4. Maintaining the heat, scrape the molten metal with the steel brush or any sharp stainless steel implement. This removes the layer of oxidation that has formed beneath the molten rod and allows it to penetrate the aluminium, preventing further oxidation.
5. Repeat this process on the other piece, if you're joining two separate pieces.
6. Position the join using clamps or sandbox.
7. Bring both pieces back up to the melting point of the rod and push together. You may then add more rod and finish by stroking a small stainless steel screwdriver blade along the join.

A strong join will only be achieved if the rod remains molten for at least 6 seconds during cooling (longer on larger castings). This allows it to form a large, strong crystalline structure. So you must ensure there is enough heat applied in a general area around the repair. For small items, the heat could be progressively reduced to slow cooling.

A few things you can do with HTS-2000:

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Pot Metal / Die Cast welding repair rods

Postby gameswat » Fri Jul 12, 2013 6:07 pm

Topic merged - Site Admin.

Nobody seems to have talked about this product, so figured I should pass on the lead.
Have been using this stuff for at least 5 years and has helped me out of countless tough situations with parts made of Unobtanium! In fact, I can honestly say that this stuff has made me thou$and$ in sales of otherwise useless machines. Here's the instuction sheet

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Cast Iron welding rods

Postby gameswat » Fri Jul 12, 2013 6:12 pm

Topic merged - Site Admin.

These rods are just amazing!! Imagine welding cast iron with just an arc welder and no pre-heating of the iron!!!!
Apparently the weld stretches as it cools so as not to stress the very delicate cast iron. I have used these to repair some delicate antique machine and other castings (well over 100 years old) that once ground down looked and worked as good as new!

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Re: Cast Iron welding rods

Postby coppinpr » Fri Jul 12, 2013 6:20 pm

These rods look to be answer to a lot problems - thanks for sharing the info.
I was recently in Lidl supermarket, always on the look out for stuff in their non-food dept and saw an arc welding kit for 39 pounds! It looked OK to my untrained eye, complete with mask and gloves! Anyone know if it's any good before I splash out? !PUZZLED!

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Example of pot metal welding repairs

Postby gameswat » Fri Jul 12, 2013 6:49 pm

Topic merged - Site Admin.

Here's a restoration job i just did a few nights ago showing what can be done using the the Muggy Weld Super Alloy (S/A) welding rods. This was for a 1959 Williams "Ten Strike" bowling arcade game. The figure was badly cracked where the gears mesh to swing the arm, and the bronze bearings were loose and sloppy due to worn pot metal. The wear was so bad that the gears had unmeshed during use and worn the teeth away. So as well as welding the body I also replaced both gears and both bearings.

1st problem: The three mounting holes into the main body casting were stripped, these hold the top casting which keeps the bearings tight. I imagine this is what caused all the problems in the fist place! Since the bowling arm is cast iron, each time it swings this creates a lot of momentum. Once the threads weakened in the lower casting, the top casting (head and shoulders) was loose and the arm movement quickly wore away the bearing holes and stripped the gears!! To repair I filled both front holes and re-tapped for original threads. But the rear hole had very little thickness to the metal so i welded a brass nut underneath so as not to have this problem ever again. The S/A sticks to brass like shite to a blanket!

2nd problem: These castings were both made using a centrifugal mold so they're not solid castings. They do this to cut down on metal usage, like a thick Easter egg. There were voids underneath three of the four bearing holes - two on the top casting and one on the bottom. These all showed signs of fatigue and missing pot metal causing some of the looseness with the bronze bushings. To say the arm was sloppy is an understatement! To repair first I laid each casting on it's side and carefully filled the three voids using gravity to assist with the flowing S/A. Then i added S/A to all the four surfaces of the bearing mounts. It was a fiddly job to machine those bearing mount holes again but I got there in the end. Next time i would tackle this issue differently though to speed up the process. I'd machine brass tubing first to the correct inner diameter, then machine/file out the worn bearing holes to take the thin sleeves of brass. Then weld the four brass halves it in place to hold the bearings, meaning very little maching, instead of welding the old worn holes and having to machine the rough surface. The repaired voids are now solid as a rock!

3rd problem: The lower main body casting had cracking and missing pot metal around where the lower gear fits, front and back. So in use this would allow the gear that fits in a brass tube to flex away from meshing with the upper gear. I welded the cracks and filled the missing areas and also added extra thickness since the original was so thin in some places.

Luckily with this job I wasn't dealing with pot metal cancer. This is where the castings crack internally and expand and warp all over the place due to a poor quality metal mixture I'm told. I've tried welding partly cancerous parts but usually even light heat applied caused the parts to literally explode! So always wear goggles if you try. These rods really work best on broken or worn parts. As I said earlier these rods really stick to brass, so on occasion I've added brass internally to strengthen a break and then welded with Super Alloy, so no brass is showing, and now stronger than new!
bowler body before 1.jpg
Lower casting showing cracked and missing metal just below where the lower gear fits inside.
bowler head before.jpg
Upper casting showing voids and missing pot metal around bearing holes.
bowler head soldering.jpg
Upper casting showing filled voids and repaired wear to bearing holes.
bowler body before 2.jpg
Lower body casting showing void and missing metal.
bowler body soldered.jpg
Lowwer casting showing welds to all damaged areas.
bowler body soldered 2.jpg
Lower casting showing outer welded repair.
bowler body filed.jpg
Lower casting showing outer sanded weld.
bowler parts x 2.jpg
Both upper and lower casting fully machined and ready to be fitted with gears.
bowler gears.jpg
New gears and bushings installed.
bowler restored.jpg
Fully restored and bowling like a champ again!

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