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Old 12-01-2006, 04:20 PM
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I need advice on mig welding cast metal.

I talked the boss man into getting some $8 dollar bar clamps from harbor freight and of course after using it day in and day out for a few weeks it has broken. It would be a shame to scrap the whole clamp because one lil piece broke. So I tried mig welding this piece back together and it failed. The weld barley penetrated into this cast metal/iron.. A magnet sticks to it pretty well. I was on the highest heat setting but the wire speed may have been a bit fast. Am I just wasting my time with this thing? Is it possible to make a strong mig weld in cast metal? I want to try it again. Any advice would be greatly appreciated.

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Old 12-01-2006, 05:16 PM
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If it is magnetic but your mig weld didn't hold, it is probably cast iron. Just braze it up.
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Old 12-01-2006, 05:45 PM
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I dont know much about brazing. I will have to look into that. Would it really be strong enough?
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Old 12-01-2006, 06:32 PM
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I know it defeats the whole "I can fix anything philosophy", but I'd buy a new one. That chinee iron is so crappy it ain't worth messing with. There is a reason it broke in the first place. It's doody.
By the time you are done brazing it you'll have more than 8.00 dollars worth of time, gas and brass in it.. But before you have an "episode" read on...

You need to "V" the 2 sides of the crack back with a file or carbide burr. Don't use an abrasive wheel, it messes up the surface of the iron. Preheat the iron some with a torch before you go to braze it. IIRC you can use oxy/acet with bronze rod. I usually use silicon bronze, but I use it with a tig welder so I don't know if you need a flux for it or not. Pile the braze up around the joint like a cast, letting it taper into the surface

Oh and when you are done, you will have a 50/50 chance that it will hold ...and if it does hold.....It will break right next to your brazed joint.

The amount of time you spend fixing it is directly proportional the the probability that it will break. And inversly proportional to relative cost of the replacement item.

In other words, You could probably buy 5 new clamps for what it will cost you to fix the broke one.

Today I broke one of the clamps that I use with my acorn table. The replacement cost is 86.00 from Acorn. I brazed that one.

Later, mikey
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Old 12-01-2006, 06:48 PM
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Well dang. That is crappy. Why do the Chinese trick me like this? This clamp is near identical to other clamps in the shop that cost $40! One crappy lil piece and the whole clamp is K-poot. The good news is we got two for the price of one. So technically we may still get our moneys worth out of the other one. For the record.. I can fix anything! Maybe I will just fab up a new aluminum or steel replacement piece..
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Old 12-02-2006, 12:35 AM
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I found this cool website with some fairly in depth explantions for some welding processes used on various metals. Here is the page on welding, brazing and doing repairs on cast iron.

http://www.welding-advisers.com/Welding-cast-iron.html

There are lots of links on the page...follow them, the info on there seems endless.

I thought it was pretty cool.

Later, mikey
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Old 12-04-2006, 11:59 PM
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You can do it NI rod stick need to preheat it and keep it raped up in burlap so it can cool slowly.

Craig
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Old 12-05-2006, 09:47 AM
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There are many different types of cast iron and the type and the end use after the repair determines the method used and whether repairing it is worth while as some types are best replaced but others can be satisfactorily repaired. It is very important to first determine WHICH type of iron you are dealing with since when you say "cast iron" you are really talking about a whole family of metals with differing characteristics. A lot of times the cheap cast iron stuff from China such as some vises, the clamp parts mentioned and a host of other cast items are so high in Carbon, Graphite and just plain junk they can not be satisfactorily welded (or even brazed) by normal means and should be replaced. Since I have seen some suspension parts made of cast iron instead of cast steel (some after-market spindles ) I thought it might be a good idea to point out that these should never be welded and NEVER,EVER heated with a torch either as a repair or modification. High strength cast iron parts are almost always malleable cast and although there are procedures for welding it the strength will be destroyed by normal welding heat, either by arc or brazing. This is just one example and these types of cast will seem to weld just fine but the basic structure of the metal will undergo a drastic change near the weld leaving it with poor strength but appearing ok, in effect setting a trap for someone. When dealing with cast iron there is no "one size fits all" method of repair.


There is excellent info on welding cast iron at the site Mikey provided the link to. It explains a lot better than most about the problems encountered when dealing with iron castings.
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Old 12-05-2006, 10:56 AM
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Got that right Oldred, I went to heat one of the clamps on my fab table so I could bend it back to it's proper shape. (It got a little bent from my neandreathal clamping activities )

I heated it evenly with my rosebud to a nice cherry red, pulled on it with a stillson wrench, and it snapped like a twig.

That was the last thing I expected. I brazed it up, I don't expect it to last though. Even though it is genuine Acorn and made in USA, the cast iron they actually used is unidentifiable. So repairing it is a hit and miss deal.

I have one repair that will need some thought, as there are not many options.. Check out the 1923 Seagrave head and barrel assembly.

1014 cubic inch inline 6 with dual underhead cams,, There are some more pics in my gallery.

I was lucky. I was able to stop a well intentioned production welder guy from whipping out the nickel rod and pounding a few passes over it with the big buzz box..

Being as how this is from a motor that was of limited production, and basically irreplaceable, it will need someone a bit smarter than me to spec the repair. I'm going to email the guy who owns that welding advisor website and see what he has to say. I think a brazed patch might be in order, because of all the creeping cracks, but that is just a guess.


Later, mikey
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Old 12-05-2006, 11:05 AM
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That one does look like a sticky one, does the crack extend into the cylinder bore? I am assuming that is a water jacket that is cracked and if so was it cracked from freezing? It looks quite large from the pic but how big is this piece? Have there been any attempts to repair it before now?

Oops, didn't notice that tape at first so now I know how big it is
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Old 12-05-2006, 11:17 AM
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Yeah it has about a 5.75" bore and a 6.5" stroke. The top of the head is over 1' across. Mountain motor.

It is cracked all along where the water jacket meets the cylinder. I think the cylinder is ok. I think it was cracked from freezing also.
There is a large pic in my gallery with all the cracks visible.

http://hotrodders.com/gallery/data/5...nder_crack.jpg
There are 2 more cylinders with similar cracks, just not as big.
Fun fun

Mikey
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Old 12-05-2006, 03:15 PM
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Oldred is right, there is a family of cast iron. and diffrent materials used to weld them. tig is a good way to repair them with the right welding materials. I have a friend that does this for a living. I got him Started in welding and he took it way past me in to welding the high tech stuff ovens heat treating gun repair aircraft parts and so on.

I just found NI rod to be a good fix all rod for most good cast stuff Does not mean its right for everything I have used it on clamps to and cylinder heads with good out comes.
Just sounded like thats what you needed to use.

But thanks oldred to point out my mistake in some of this cast iron from China is just junk. Its hard to tell whats in it tell you try weld it. what ever happened to made in america?


Craig
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Old 12-05-2006, 04:27 PM
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Yeah this thing does not look like good cast iron. It looks like the di cast stuff my toy guns were made out of as a kid. I have decided not to try and weld it. I am going to cut up a steel c clamp and use that to fab up a new steel part for the bar clamp. Welding cast iron is over my head right now I think anyway but this is good advise I can refer back to when I am ready. Thanks fellas.
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Old 12-11-2006, 12:38 PM
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power, I think brazing is the best fix for that water jacket also. Just remember to stop drill the ends of the cracks where you can. Even if you don't go all the way through a drilled hole should stop the cracking at the ends.

One valve on each side to the cylinder is called a "T-head" due to the shape of the combustion chamber on top of the cylinder. A flat head Ford V-8 (and most automotive engines, as well as the typical Briggs & Stratton) is technically an "L-head" for the same reason (bore and chamber form an upside down "L"). The only one that doesn't make obvious sense is the "F-head". It has one valve in the block (exhaust) and one in the head (intake) like a typical OHV. I guess an "F" fits as well as any other letter would! The only maufacturer I know of to use an F-head in production is Willys -- the L-head four cylinder Jeep engine was upgraded by an F-head conversion to get a little more compression and power. Not many T-head engines were made!
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Old 12-13-2006, 10:40 AM
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This is my fix for the broke bar clamp. It works and its strong, but it ain't pretty!
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