I have a two pieces of cast iron that are to be joined with a 3/8" machine screw through flanges. Each flange is roughly 1 1/2" x 2 " and 1/2" thick. My problem is the hole in the top piece is about 1/4" displaced from the hole in the bottom piece. When completed the piece are subject to some lateral stress but no heat.
Since the hole in the bottom piece is threaded and hole in the top piece is not the ideal thing would be to fill the hole in the top piece and redrill it. Some of the new hole is going to overlap the filler of the old hole so I am not sure what will hold up. Metal-epoxy ? Some kind of filler rod (I have an O/A torch).
Getting another casting would be expensive. Also, due to the shape of the casting sawing off the flange and welding another in place would be very difficult.
Any help most appreciated!
The ideal solution is to fill the non-threaded hole by brazing it shut with a special cast-iron brazing filler rod. You can use for O/A torch to do this. Then redrill as you said.
I've used HTS-528 brazing rod and it works as advertised, although you'll want to practice a couple times on some scrap cast iron to get the hang of it. You can read about HTS-528 brazing rod at http://www.brazingrod.com/hts528.htm
It costs $75 per pound so it ain't free.
I've had good results using cast iron welding rod and the oxy-acetylene torch. Make sure you heat the entire casting to about 400 - 500 degrees before you use concentrated heat in the area to be welded. Cover the part with blankets or better yet, start a charcoal fire before you start the weld so that the fire is well burned by the time you complete the weld. Place the welded part in the charcoal fire and let it burn itself out. This will ensure very slow cooling and prevent cracking problems.
Don't try to hurry the process. Countersink the hole to provide good access. You may have to use a stirring action when you apply the cast iron filler metal to the joint. Cast iron melts at a lower temperature than steel and it forms a "wet" or very fluid puddle compared to steel.
Again, I've had very good results with making repairs in cast iron provided the entire casting is adequately preheated and slowly cooled by means of placing the part in the charcoal fire after the welding was completed. The price of a 10 to 50 pound bag of charcoal is good insurance against cracking and hard brittle HAZ adjacent to the weld.
I don't recommend preheating the part in your wife's electric range. My wife didn't take kindly to me "baking" oily cast iron parts in the kitchen before welding them. No sense of humor!
Good luck - Al
I have always heard to avoid if at all possible welding cast iron. So my non welding approach to repairing this would be to simply recenter an OVERSIZED clearance hole centered exactly over the threaded hole completely engulfing the diameter of the improperly centered hole and then simply find/buy/machine a 1/2" thick bushing to correct the oversize ... this bushing might even be flanged and sized to lightly press in so that it will stay in place even if the halves are often seperated for maintenance or whatever... if not then just a plain non lipped bushing with oversized fender washer on top! Heck if this is something non precision, non pressurized, can't leak anything etc etc you might even get away with just a heavy guage fender washer alone!... I would bush it no matter what it's use though ...being the perfectionist sort and loving precision.
I think you will find this an elegant and ideal solution .... i just hope it is not too offered too late for you to use? ... If so, I'm sorry I just today signed on to the list for the first time!
Good Luck! Doug
Great idea and not too late. I bought some silicon bronze brazing rod and have been learning how to use it but have been too cautious (i.e. chicken) to try it on the casting yet. The holes may be too misaligned to make your suggestion work but I'll check it out as soon as I get some time to spend in the shop. Thank you!
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