Hi. I read in the Internet that a broken back gear tooth can be fixed by making a new one out of cast iron, slotting the broken spot in the gear, and silver soldering the replacement tooth in. I tried this and had problems. It was difficult to get the assembly hot enough without overheating the tooth. The problem is that the tooth does not have good thermal contact with the rest of the gear, and the flame is just too hot. A National propane-oxygen torch was used.
Since there are suggestions all over the Internet about silver soldering gear teeth, I decided to look at Youtube. Interestingly enough, there are no clear examples. There is a video by Halligan showing him building up silver solder with an air acetylene torch, which has a much softer flame. The problem about this is it does not involve that pesky small piece of cast iron. The most intriguing example is a video by Keith Rucker which clearly states that he is silver soldering in a tooth machined out of a cast iron bar. There is a beautiful illustration of him machining the tooth. But the part where the tooth is silver soldered in is missing!!!!!!!!!!!! He states that the camera ran out of memory, so all the footage was lost. Way down in the comments, there is someone who voices his suspicion that the silver soldering didn't go so well. The commenter points to a visible gap on the side of the tooth after silver soldering. It is pretty well known to those well practiced in the art that there should be a fillet in the gap. Anyway the commenter makes some pointed statements about the missing segment of video. Normally, I do not take most comments to Youtube videos seriously, since there is a lot of noise. But there is one noise that is unmistakable. That is the ping sound of an incompletely silver soldered cast iron replacement tooth breaking free during a test and followed a fraction of a second later by the sickening sound of that tooth hitting the floor. This noise made me really sensitive to that negative comment to Keith Rucker's video, which was otherwise excellent. Are there any videos showing the job done successfully?
Since there are suggestions all over the Internet about silver soldering gear teeth, I decided to look at Youtube. Interestingly enough, there are no clear examples. There is a video by Halligan showing him building up silver solder with an air acetylene torch, which has a much softer flame. The problem about this is it does not involve that pesky small piece of cast iron. The most intriguing example is a video by Keith Rucker which clearly states that he is silver soldering in a tooth machined out of a cast iron bar. There is a beautiful illustration of him machining the tooth. But the part where the tooth is silver soldered in is missing!!!!!!!!!!!! He states that the camera ran out of memory, so all the footage was lost. Way down in the comments, there is someone who voices his suspicion that the silver soldering didn't go so well. The commenter points to a visible gap on the side of the tooth after silver soldering. It is pretty well known to those well practiced in the art that there should be a fillet in the gap. Anyway the commenter makes some pointed statements about the missing segment of video. Normally, I do not take most comments to Youtube videos seriously, since there is a lot of noise. But there is one noise that is unmistakable. That is the ping sound of an incompletely silver soldered cast iron replacement tooth breaking free during a test and followed a fraction of a second later by the sickening sound of that tooth hitting the floor. This noise made me really sensitive to that negative comment to Keith Rucker's video, which was otherwise excellent. Are there any videos showing the job done successfully?