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Speaking of machine repairs that mght be thought doubtful

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  • Speaking of machine repairs that mght be thought doubtful

    Here are a couple that were done on the Lewis many years ago by some previous owner. Brazed repairs that have never caused any problems, despite being in fairly high stress areas.

    One is on the arbor support



    The other is on one of the dovetails of the knee. Many would run away from the machine, screaming with their hair on fire.....


    2730

    Keep eye on ball.
    Hashim Khan


    It's just a box of rain, I don't know who put it there.

  • #2
    Brazed repairs unfortunately have unjustifiably been given the dubious distinction of being a hacked repair.
    Properly executed with fit-up tolerances held tight they are often stronger than the parent metal itself. I have plenty of examples around the yard that were done decades ago and are still doing fine.
    Airplane and motorcycle frames were often braze assembled in the past due to this being a very sound method, your examples underscore this often maligned procedure as being a worthy option.
    I love the process!
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories​

    Location: British Columbia

    Comment


    • #3
      Willy is right, brazing was a very common form of repair in the past. I can remember as a kid almost all steel and cast iron repairs were brazed. Exhaust systems, body panels lawn mower parts, water pumps etc. It was cheap and common. Most every shop / gas station repair garage had a set of oxy. act. tanks. Brass rod was either plain or flux coated. Some preferred dipping the rod in a can of flux. If flux coated rod wasn't stored properly and handled carefully the flux would come off. Only until the TIG machines and various types of spray weld processes have become more common and less expensive now brazing is being seen as an inferior repair or back yard hack. Not so !

      JL..............

      Comment


      • #4
        Originally posted by JoeLee View Post
        Willy is right, brazing was a very common form of repair in the past. I can remember as a kid almost all steel and cast iron repairs were brazed. Exhaust systems, body panels lawn mower parts, water pumps etc. It was cheap and common. Most every shop / gas station repair garage had a set of oxy. act. tanks. Brass rod was either plain or flux coated. Some preferred dipping the rod in a can of flux. If flux coated rod wasn't stored properly and handled carefully the flux would come off. Only until the TIG machines and various types of spray weld processes have become more common and less expensive now brazing is being seen as an inferior repair or back yard hack. Not so !

        JL..............
        Don't you mean bronze rod?
        OPEN EYES, OPEN EARS, OPEN MIND

        THINK HARDER

        BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

        MY NAME IS BRIAN AND I AM A TOOLOHOLIC

        Comment


        • #5
          I've had great luck with brazing cast iron. The secret is in preheating the cast iron until the bronze flows and sticks. Once it's hot enough it brazes pretty much like steel.
          OPEN EYES, OPEN EARS, OPEN MIND

          THINK HARDER

          BETTER TO HAVE TOOLS YOU DON'T NEED THAN TO NEED TOOLS YOU DON'T HAVE

          MY NAME IS BRIAN AND I AM A TOOLOHOLIC

          Comment


          • #6
            Originally posted by Willy View Post
            Brazed repairs unfortunately have unjustifiably been given the dubious distinction of being a hacked repair....

            Funny you say that about their perceived reputation in your mind regarding braze repairs.
            I actually have the opposite reaction.
            When I see a weld repair in cast iron, I immediately assume in my mind that is is hacked
            and proper perheat and post slow cool was not done. And If I have to mess with an
            improperly fitted up welded repair joint, the iron is likely glass hard and cracked next
            to the weld.
            When I see a braze joint repair, I think you have a good chance of it being done properly.
            Number one, with a torch, you have more heat and less temperature than an electric weld.
            So you automatically have preheat from the torch, and so much heat input that the part wll
            cool slow, or at least slower than electric welding. The temperatures of electric welding are
            (obviously) melting the iron, and if you do not cool slower than the critical cooling curve
            dictates, you will get cementite, or iron carbides and the resulting brittle heat effected zone.
            Bronze braze is 60,000 psi tensile, iron is likely half that. So braze is very strong. My preferred
            method of repair.

            -D
            DZER

            Comment


            • #7
              No idea why people think brazing is a hack, it's a well-established standard method. As Doozer notes, actual welding of cast iron requires skill and preparation that is usually lacking. Even a small job can easily take all day if it's being done right.
              25 miles north of Buffalo NY, USA

              Comment


              • #8
                You may or may not be impressed with the repair done to the museum's Smart & Brown when it was owned by Westland Helicopters, between 20 and 70 years ago. Preheating was not high on the agenda, merely getting the bits back on. I wonder if somebody dropped a chuck on the stand, and what flowery language was forthcoming?

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                • #9
                  Originally posted by bborr01 View Post

                  Don't you mean bronze rod?
                  Several types...........

                  https://www.forneyind.com/products/w...8-x-18-10-rods

                  https://www.forneyind.com/products/b...32-x-36-10-lbs

                  JL..............

                  Comment


                  • #10
                    I TiG brazed some copper starter solenoid contacts the other day on a Nippon Denso starter.
                    It worked out great. Layed down perfect with just a little crown. Milled it flat, and now it is
                    better than original, as the factory contact was just copper.

                    -Doozer

                    Edit- Sorry, I meant I silver brazed a new surface to the copper. Brain fart that I did not say that.
                    Last edited by Doozer; 06-10-2021, 04:24 PM.
                    DZER

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                    • #11
                      Originally posted by Doozer View Post
                      I TiG brazed some copper starter solenoid contacts the other day on a Nippon Denso starter.
                      It worked out great. Layed down perfect with just a little crown. Milled it flat, and now it is
                      better than original, as the factory contact was just copper.

                      -Doozer
                      Except for conductivity.
                      Location: Saskatoon, Saskatchewan, Canada

                      Comment


                      • #12
                        Conductivity is not usually the main issue with contacts. They form a small part of the circuit. The main influence is contact resistance, which is dependent on surface conditions more than bulk properties.

                        Unfortunately, alloys do have lower melting temps than pure metals. That is not ideal for contacts, but if it works, it works.

                        The melting temp may not be a big issue if the contact mass is large enough compared with the available arc energy. The arc is hotter than most any metal melts, so.......... There is contact welding present to some degree in nearly every switch or relay.
                        2730

                        Keep eye on ball.
                        Hashim Khan


                        It's just a box of rain, I don't know who put it there.

                        Comment


                        • #13
                          I've got no problem with welding cast irons. I either use 98%Ni rods or Inconel 82 wire (brilliant stuff), plus preheat and gentle cooling. The little BCA jig borer that I'm cleaning up and inspecting has, however, got one of the other sort of weld repairs. It's on a clamp and I have to wonder how long it was before it broke. Haven't yet worked out whether it's a repair or replace job.
                          Location- Rugby, Warwickshire. UK

                          Comment


                          • #14
                            Originally posted by Doozer View Post


                            Funny you say that about their perceived reputation in your mind regarding braze repairs.
                            I actually have the opposite reaction.
                            When I see a weld repair in cast iron, I immediately assume in my mind that is is hacked
                            and proper perheat and post slow cool was not done. And If I have to mess with an
                            improperly fitted up welded repair joint, the iron is likely glass hard and cracked next
                            to the weld.
                            When I see a braze joint repair, I think you have a good chance of it being done properly.
                            Number one, with a torch, you have more heat and less temperature than an electric weld.
                            So you automatically have preheat from the torch, and so much heat input that the part wll
                            cool slow, or at least slower than electric welding. The temperatures of electric welding are
                            (obviously) melting the iron, and if you do not cool slower than the critical cooling curve
                            dictates, you will get cementite, or iron carbides and the resulting brittle heat effected zone.
                            Bronze braze is 60,000 psi tensile, iron is likely half that. So braze is very strong. My preferred
                            method of repair.

                            -D
                            Not a bad perceived reputation in my mind, but a bad perceived reputation in my experience when seeing how the process is executed and how it is accepted as an option. This tells me that I am not alone in seeing badly executed brazed repairs.

                            But yes whether an improper procedural execution of cast iron welding or of a brazed joint, shoddy adherence to accepted guidelines are prevalent in both processes.
                            I see a lot of failed joints in both processes, although mostly in brazing. The fact that more folks will attempt brazing due to it being an easier process to get into also speaks volumes about the outcome, both good and bad.
                            Most folks with a torch and a brazing rod will attempt brazing and yet have no idea of proper heat input, fit-up, or the fact that without a clean surface the capillary action that is paramount to a successful outcome is not achieved. Lots of brass gobbed on the outside yet nothing at the root of the joint itself.

                            This fact has in my experience given the process a black eye that it does not deserve.
                            Home, down in the valley behind the Red Angus
                            Bad Decisions Make Good Stories​

                            Location: British Columbia

                            Comment


                            • #15
                              Originally posted by Doozer View Post
                              I TiG brazed some copper starter solenoid contacts the other day on a Nippon Denso starter.
                              It worked out great. Layed down perfect with just a little crown. Milled it flat, and now it is
                              better than original, as the factory contact was just copper.

                              -Doozer
                              Did is smoke ?? I've TIG'ged bronze and brass props, works fine just a lot of white smoke and soot.

                              JL...........

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