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1988 Jet JMD-18 with cracked head casting.

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  • #16
    It could be welded by someone who knows what they are doing. But ...... by the time you pay the welder, you won't save much compared to the $300 Grizzly replacement part.

    If it were mine, I'd grind out the cracks (which might be a chore in itself, since some of it appears difficult to access), preheat the dickens out of it, and weld her up with nickel rod (about $35 per pound).

    If you are not comfortable doing the repair yourself, you might as well spring for the $300 Grizzly part.

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    • #17
      It is difficult to get an idea of the area needing repair due to the closeup photos. In many cases, it is possible to drill & tap the broken part and bolt a strap bandaid to hold the pieces together. Ugly, but cheap and effective.

      If it were mine, and I could not bandaid it, I would V it out and braze. Preheat the area well, and slow cool by burying in vermiculite. If it works, you are out only the cost of the gas & brazing rod. Brazing cast iron is not too difficult to master, welding is a different story.

      In either case, drill a small hole at the end of the crack to prevent further propogation.
      Jim H.

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      • #18
        I see several recommendations to have this thing welded but it has been my experience that those Chinese iron castings are nearly impossible to weld, some are in fact impossible. I speak from experience, well over 35 years repairing and rebuilding mining equipment, and during that time I saw everything from machine shop equipment to small items like vises, etc. Almost all of it was a very poor candidate for welding but most parts could be successfully brazed with Bronze filler metal although some of it could not even be brazed! If you decide to go the welding route brazing would almost certainly be the best choice and don't underestimate the strength of a properly done brazing repair since when dealing with these castings it will often be stronger than the parent metal.

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        • #19
          I agree with those who suggest that welding or brazing is the way to fix the cracked head. With sufficient V-eeing and good preheat, it will weld or braze very nicely.

          I one brazed an exhaust manifold on a 4 cylinder Mercury car of some sort for a friend. (Capri?) It was broken off just above the exhaust pipe flange. We beveled the broken parts, fitted them up and then heated the manifold for about 20 minutes with a torch. I don't know the exact temperature but we got it very hot

          I used standard brazing rod with the white flux and my O-A torch with a large tip.. Once the preheat was done, the brass flowed beautifully and made a neat repair. We let it cool for the remainder of the day. I understand that it was still holding when he sold the car several years later.

          I think a professional welder with the proper nickel rod could do a nice job for you if you don't want to do it yourself. Proper preheat and proper post-cooling could minimize any warpage.

          Good luck.

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          • #20
            Originally posted by MTNGUN
            weld her up with nickel rod (about $35 per pound).

            I have serious doubts as to successfully welding even with Nickel rod but at $35 a pound you must be talking about Ni99 rod which would not be necessary here. Most people seem to think that because it is so expensive the Ni99 must be a stronger rod that would be less likely to crack than the MUCH cheaper Ni55 but that is a misunderstanding. The Ni55 is a better choice for more than just price because the extra money for the Ni99 buys you the ability to machine the the weld unlike the cheaper (and slightly stronger) Ni55. So unless the weld will need to be machined after welding the much Cheaper Nickel rod is the one to use, that is if this thing turns out to even be weldable.

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            • #21
              Since the crack does cross a gasketed sealing surface (If I read the pics correctly), I would tend toward brazing too. Even if you cannot machine that surface back to flat, you will need to work some magic with a hand file to get that to seal again...and that is much better done with brazing.

              The other issue is that the iron may well have some embedded oil. Lots of soaking in lacquer thinner may help, but oily iron does not braze well, so get it clean first.

              As advised, v the crack and some would advise to drill through the end of the current crack to keep it from spreading. That hole can be brazed back shut. It's been years since I even brazed cast iron, but I have seen some good repairs....and some not so good.

              Paul
              Paul Carpenter
              Mapleton, IL

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              • #22
                IMHO brazing with a good bronze alloy rod (not the auto parts store variety) from a welding supply would be the way to fix this thing. This would make for a very sound and strong repair and the resulting weld would machine easily, beautifully in fact. The problem with brazing is that most people seem to think that it is an inferior process that results in a weld that is little more than a glue joint but it is in fact a very good way to repair an iron casting that rivals, and often exceeds, the parent metal in strength.

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                • #23
                  I have had good luck repairing things like this with Tig brazing, using a silicon bronze filler rod.
                  No preheat, no post heat, no burning off lots of paint, just surgical repair.
                  Grind a V, nip in there with a 1/16" diameter silly bronze filler rod, DC, argon gas, takes ten or fifteen minutes, and you are done.

                  You can also get Nickel Tig rod- which is a lot less wasteful than trying to stick weld nickel, at the prices they get for nickel rod these days.
                  Some welding supply places still will sell you either of these rods by the pound, which means you just buy a few.
                  Nickel will stick pretty good to most cast iron, and is a strong weld. Again, with Tig, no preheat or postheat needed.
                  I did a lot of this at Repair Days, at the Metals Museum, in Memphis, a couple of years ago, when I volunteered- and the range of quality of cast iron that came in was pretty broad- some high quality american antiques, and some bottom of the barrel chinese imports. The nickel tig rod stuck to all of em, just fine.

                  (by the way, Repair Days is a hoot- I heartily recommend anyone volunteering- you meet the most amazing metalworkers, have a great weekend, and help a great cause- )
                  http://www.metalmuseum.org/repair_days.html


                  Find someone with a tig welder, and it should be a relatively quick fix.

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                  • #24
                    Would you expound on tig brazing with the silicon bronze rod (either here or in the welding forum)? I have seen some work done with it (after the work was complete) and it's a very neat process...no brazing flux mess or black suet marks etc. It seemed to lend itself to a very good looking bead in the applications I saw...and...importantly for us who machine stuff...it's machinable after the fact with just about anything. If anything, you have likely annealed the base metal.

                    What baffles me just a bit is that TIG welding (or any welding) involves melting the base metal. Brazing differs in that the base metal is not melted, just heated to a temp that will melt the filler rod. Its pretty easy to moderate the metal temp with an oxy-acetylene torch. Theoretically, it ought to be easy with a TIG torch since you also have a pedal to vary the arc intensity. On the other hand, the arc is...well...arc temperature (very hot) I would think that at its minimum, you would too readily be melting the base metal as you warmed it enough to melt the rod??? With an O2 torch, you can always pull the flame back if you start to see the sparks that betray the fact that the base metal is melting. Back off too far on the TIG pedal, however, and the arc goes out and your rod is stuck in the puddle.

                    However, like so many things, I over-complicate it and then try it and figure out it was not as complicated as I made it to be in my head, so maybe this is not so tough after all

                    Paul
                    Paul Carpenter
                    Mapleton, IL

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                    • #25
                      By using the foot pedal, its pretty easy to braze with a tig machine.
                      I have been doing it for 20 years or so now, and its not rocket science.

                      You just dont use as many amps.

                      I used to produce a line of candlesticks which required attaching a 22 gage stamped steel leaf to a 3/8" round bar "branch", and tig brazing was the perfect application for that- you heat up the 3/8" round, add a dollop of brazing rod, and gently work it onto the leaf. The proverbial "razor blade to a propeller shaft" problem.

                      With cast iron, its actually easier than those radical material thickness variations- You heat the base metal, in this case the cast iron, up enough so that the silly bronze rod melts when it is touched to it, then, you actually work ahead of the braze with the torch- you dont melt the filler rod with the arc, you allow the hot cast iron to melt the filler rod, while you are heating the next area of cast- its easier to do, than to describe.

                      Tig brazing also works great on thin wall tubing. I once took a class from Ron Fournier, famous Detroit auto fabricator. While he is mostly known for his skills at metalshaping, and gas welding aluminum, he also has fabricated more tube frames for cars than most of us have seen in our lifetimes- and he usually uses a silicon bronze filler rod to braze together square and round tubing for this. He says it causes less heat distortion in the thinwall tubing, and is just as strong as welding.

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                      • #26
                        Ries has it correct; think of TIG as no more than an inert, tightly focused flame. The base metal doesn't melt, you just need to get it up to the temp to melt the brazing filler.

                        However, TIG is extremely picky for cleanliness. I disagree with him about the "grind and go" comment. On any casting that has had oil in it(or anywhere near it) , it can be problematic to get it to weld/braze properly because of oil permeated in the casting in the crack. The best method I have found is to use the TIG torch as a "wash clean"; go over the cracked area with the arc at a lower current setting to burn out the oil, stop, cool, clean with solvent, wash with arc again, stop, cool clean. You can see when you are ready when the arc smoking and carbon deposits go away.

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                        • #27
                          Jeff is right about oil.
                          Especially engine or auto parts.
                          Oil can really soak into cast iron, and screw up welds or brazing.

                          But the pics of this mill drill dont show a particularly oil soaked crack.

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                          • #28
                            Originally posted by Ries
                            ...Tig brazing...
                            Neat, I gotta try that! Once again I'm amazed at the the breadth of knowledge on this board.

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                            • #29
                              I definitely picked the right forum to jump in with, the wealth of knowledge is amazing.

                              I am going to try and braze the crack this weekend. The TIG approach is very tempting as I have access to a TIG welder and have done a great deal of it ( I teach basic steel and aluminum TIG welding in my classes).

                              Ries,

                              I take it you strike up an arc but not with enough current to cause a puddle to form? Which polarity provides the best results?

                              If I go with the standard torch heating, must I pre-heat the entire casting or can I preheat the local area and heat less as I gradually make it further from the crack? Thanks

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                              • #30
                                I'm with banjoallen, I have seen a large crack in a marine engine cylinder stitched and chain plugged. A super system with no heat distortion and strong. Peter
                                The difficult done right away. the impossible takes a little time.

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