48willys Posted July 11, 2009 Share Posted July 11, 2009 (edited) I'm wanting to fix my little forge that I started on, and needed a little help. First, the pan is cracked badly,it go's all the way from the center of the pan to the outside.Also about my air gate,how should it be made?I'm guessing that I have it wrong and the blower should be bolted to the pan and the grate sits on the pan.How would I fix the pan?"]http:// I know I have a few things wrong,because at the time I fixed it up,I had found it in a dump, it was broken apart and all I had to go by was a reprint of a picture in a 1909 sears catalog.Also what should I make my drive belt from? Edited July 11, 2009 by 48willys Quote Link to comment Share on other sites More sharing options...
wd&mlteach Posted July 11, 2009 Share Posted July 11, 2009 I am not an expert by any means but that crack is a tough one. Your firepot is made from cast iron and from my experience cast iron is really tough to weld. Back in my younger days somebody once told me that you can't weld cast iron and I set out to prove them wrong. So I went to the scrap yard and got a brake drum, cracked it with a sledge hammer, tried to weld it back together. It ended up looking like a fish skeleton by the time I was done. I then researched into some other methods and tried again, still it did not work. What I have found out is that if you want to weld cast iron you have to heat the whole thing up to cherry red. This can be done in a furnace or have a bunch of guys painting it with rosebud torches. It takes a bunch of guys because it is hot work and it is nice to be able to change out when you really start sweating. Then when the whole thing is hot enough weld it quickly and control cool down rate. The whole time pray you do not get any more cracks. If you do not have a furnace big enough or a bunch of guys with Oxy-A torches your fixes are limited to finding somebody else to weld it(good luck with that), have a new one cast(too expensive), construct a new firepot and stand( my choice), or physical band-aids. If it were me I would choose to construct a new stand and firepot but I do not know what is available to you as far as tooling or supplies. The other option that might buy you some time is some band-aids made from 1/8” x 1” x 2” HR steel. Firepots are usually pretty thick and can be drilled and tapped. I would make a couple of these band-aids and strategically place them around the crack on the outside of the pot by drilling and tapping some holes maybe Quote Link to comment Share on other sites More sharing options...
David Einhorn Posted July 11, 2009 Share Posted July 11, 2009 (edited) At the risk of being told that I am an idiot....... I have had good results welding cast iron with nickle welding rod (labeled for cast iron) from the farm store. Recently I welded a broken cast iron fry pan, and also welded some 1/2" nuts to a cast iron fireback. Of course I did it the "wrong" way by not pre-heating. So far none of my welds, over the years, have broken or cracked. The cracks on your pan appear to be closed. In your position, I would figure that I had nothing to loose so I would weld a few 1" beads along the bottom, relieving each one with some hammer taps, and see what happens. If you are concerned about how it would turn out, find a professional welder in your area. Many years ago, a professional welder in the local blacksmith guild welded a cast iron floor-mandrel to a steel plate to serve as a base, charged me nothing, and all the welds have held perfectly for over 22 years../.. and I almost forgot to say, he did not preheat anything either. Edited July 11, 2009 by UnicornForge Quote Link to comment Share on other sites More sharing options...
wd&mlteach Posted July 11, 2009 Share Posted July 11, 2009 UnicornForge I do not think you are an idiot. According to my Forney ARC welding book that is exactly how it is done, weld a bit, allow it to cool down while light hammering, and weld a bit more -repeat. The whole process is kinda like stitching it back together with short welds to keep the heat down. From what I understand the Nickel rods are also designed to stretch a bit to help with the cracking. The whole process makes sense to me, you might have inspired me to give it another try. The next time I am at Sahd's I will pick up some more cast and try it again. Maybe what I tried was too thin, hummmm?!? Quote Link to comment Share on other sites More sharing options...
48willys Posted July 11, 2009 Author Share Posted July 11, 2009 That was my first thought,use the Nickel rods,but I'v never tried to do somthing this large or this shape.So my two best options would be to get the whole thing hot and braze it or use Nickel rods and keep it cool like when welding sheetmetal? Quote Link to comment Share on other sites More sharing options...
wd&mlteach Posted July 11, 2009 Share Posted July 11, 2009 I do not think brazing would hold up to high temperatures around the tuyere, but I could be wrong. I have not worked with brazing much, if my memory is correct I think the melt temperature is around 800 degrees? I am not sure how hot the actual firepot gets but I would think it could get to this temperature or go over easily, especially if you were trying to weld in it. Quote Link to comment Share on other sites More sharing options...
48willys Posted July 11, 2009 Author Share Posted July 11, 2009 That's true,I didn't think about it might melt.I never could get it near welding heat though,but that might be the tuyere,because I have it together wrong.I'll try the rods and see how it works. Quote Link to comment Share on other sites More sharing options...
Charlotte Posted July 11, 2009 Share Posted July 11, 2009 I do not think brazing would hold up to high temperatures around the tuyere, but I could be wrong. I have not worked with brazing much, if my memory is correct I think the melt temperature is around 800 degrees? I am not sure how hot the actual firepot gets but I would think it could get to this temperature or go over easily, especially if you were trying to weld in it. Silver brazing, high temp type> 1150 degree. Brass brazing around 1700 deg. Personally If i had a choice for a fire pot I would go with nickle rod. I've seen a lot of them work for a long time. Even seen cracked heads reapired that way back in the day when I was and innocent bystander. Quote Link to comment Share on other sites More sharing options...
wd&mlteach Posted July 12, 2009 Share Posted July 12, 2009 Charlotte you are right I do not know what I was thinking. I melt Aluminum all of the time in my crucible furnace and I know(or at least I think I do, lately, I do not think I know anything) that is around 1200 F. I also know Brass has a higher melting point, so what I said earlier does not make sense. Is 800 F the temperature that the flux starts melt? Why is that temperature in my head stored under the brazing file? Quote Link to comment Share on other sites More sharing options...
Charlotte Posted July 12, 2009 Share Posted July 12, 2009 I'm not sure what the temperature 800 relates too, unless it is partculiar flux or alloy. Borax goes anhydrous around 400 deg F and completly melts around 1300. Pure Aluminum melts around 1220 and pure lead around 620. Zinc melts around 787 degree F. There is an aluminum zinc alloy that is used in automobiles for door handles and such with a temperature of around 800 +. The parts are made by injection molding. I don't know what the specific alloy is but at one time I worked with an industrial engineer that was responsible for supervising the operation on one of those lines. Evidently the metal alloy Zinc+ Al+ ? +? (could be tin/copper/bismuth antimony ...) didn't shrink much and released cleanly from the molds provide the mold and metal temperature were maintained correctly. Some times it is referred to as pot metal. Quote Link to comment Share on other sites More sharing options...
48willys Posted July 15, 2009 Author Share Posted July 15, 2009 Well I worked on stitching it back together with the nickle rod and I think it will hold.I'm not so sure about the smaller cracks at the bolt holes but I'll use large washers to keep the pressure off the cracks. Only one other thing,would it hurt anything to line the pan?It's really thin in spots and I think that the heat might have had a part in the crack,because the big one showed up while it was cooling. Quote Link to comment Share on other sites More sharing options...
Dave Leppo Posted July 16, 2009 Share Posted July 16, 2009 I just finished a forge refurbish / upgrade, starting with a similar portable forge as yours. After getting new legs, cleaning the gearbox, and repairing a crack with a firepot.pdf Quote Link to comment Share on other sites More sharing options...
raypa Posted September 1, 2009 Share Posted September 1, 2009 My center is approximately 12" dia and about 2" deep and is cast steel. That is where I have been making the fire. I have not made a fire that has been larger than that yet. I foresee when I try something larger I will need some clay. I need to get a picture up here. Quote Link to comment Share on other sites More sharing options...
raypa Posted September 1, 2009 Share Posted September 1, 2009 Here is the picture. Where the fire is now, that is all cast. the outer pan is not. so I should put clay on the outer pan. right. Quote Link to comment Share on other sites More sharing options...
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