How to braze

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Ok guys I thought I would start a thread on brazing.   Everybody feel free to add to this as well as my cutting torch thread. I'm just trying to get some of this info in one spot.   I'll start out with this video and a copy of what I wrote on another thread. I'm not 100% happy with the video and don't plan on doing to many more till I manage to get a camera that's capable of more detail in the bright areas of the torch while still showing what's going on around it.   Here's the video. It's kinda long but I try to cover a fair amount in it. First off let me say that I've not done a whole lot of TIG brazing. I've tried it on a few things a quickly went back to using the torch. It has it's place but IMHO not on cast iron.Let's just start by saying that the whole key to doing a good job with cast iron is preheat, maintaining heat in the piece, and slow even cooling of the piece. All of which points towards torch work. TIG is a concentrated heat where you're just heating a small area. This fine even preferred for most welding just not cast iron.Doing what I do with cast iron (machining it afterwords) dramatically shows the need for all of this heat. If it's not done that way then the cast iron next to the weld will be so hard you can barely scratch it with a carbide tool.Now to give a example lets say that you're going to weld some high carbon steel. What do you do? You preheat the piece, maintain a proper heat level while welding, and post heat with controlled cool down.Stop and think about this next point.High carbon steel has a maximum of 2% carbon and that's the absolute maximum it can hold nearly all carbon steels in the real world are less than 1% carbon. Many much less. 4140 for example has 0.4% carbon in it.By definition cast iron always has more carbon. So much in fact that the iron can't hold it all and it's precipitated out into the iron matrix in one of several forms depending on the type and heat treat of the cast iron.What I'm trying to get across here is the fact that you have to treat cast iron as if it was the highest carbon steel you've ever welded (which it is).I'm not enough of a expert to try and discuss the details of all the different forms on iron and carbon mixes but I know enough and have experienced enough to know the above is true. Now onto the more practical matters.First off is proper cleaning and preparation of the joint. This is critical. You may well need to heat the piece and let it cool to get all the excess oil and crap that's soaked into the cast iron over the years. However if you do the burn in like is described above then you will have to redo the surface preparation if you want the brass to flow into the cast iron like it needs to for a good bond. Clean unburned surface is needed for a good bond and there's a few key points to that.First point is grinding smears the carbon on the surface making it difficult to get a good flow of the brass. This means that some other means is needed for the final surface prep even if you use the grinder for the majority of the removal.I use one of two methods to do the final prep. I either sand blast the surface to be bonded thoroughly or you need to use a sharp (and I mean sharp) cutting tool of some form. A sharp file can work on simple shapes but my most used method is a sharp carbide burr in a die grinder.Next point is to not overheat the area you're fixing to braze while bringing the piece up to temperature. If you overheat and burn the area then the brass will not flow properly and you'll be forced to try and burn it into the piece. This can be tricky on some pieces and I'll often flow the brass along the top of the V joint first to prevent this surface burning since the sharp edge has a tendency to overheat while you're working at getting the brass to flow in the bottom of the joint. This is where proper and enough preheat of the overall piece is crucial. It's best to start you're heating by heating beside the joint you're brazing rather than right at the joint. Only once you get enough heat soaked into the piece can you really get to work flowing the brass out.Another tip is to use a larger tip than you think you need. You need to keep the flame low enough that it doesn't blow the brass away while you're working. As well as you need to heat the larger overall piece rather than a pin point heat. Pin point heat will make for boiling of the zinc out of the brass causing it to not flow properly and creating bubbles in the finished piece. You can switch to a small tip for the final building up and shaping of the brass joint but only after getting a good flow of brass on the overall piece.If for some reason you accidentally overheat part of the piece and the brass stops flowing on you then you need to let it cool and prepare the the surface again. This is often the case when you're doing both sides of the piece. Getting the first side flowed out will tend to burn the other side making it difficult or impossible to get a good flow. Ideally the whole piece would be covered in flux when you're heating it but it's pretty much impossible to get it all covered without having problems like this. It is something that you should work towards.That brings up the discussion of flux. I prefer the Peterson brand myself but they make more than one kind. Unfortunately the absolute best flux for cast was there #3 (for cast and malleable at low to medium heat) which was a two part flux. It worked very well even on dirty cast iron. However they don't make it any more. They do make a #2 (for cast and malleable at high heat). It's not as good but sometimes it will let you bond to a piece that won't let you stick in any other way. I usually keep a can of it open and nearby so that I can use it for those small difficult areas that crop up sometimes. It's not the perfect flux though. It tends to bubble the brass while you're working leaving bubbles in the finish work and it doesn't flow as well as the standard #1. Thus there's times when I'll mix the two if the piece is giving me trouble. Sometimes I'm forced to use the #2 for the first pass and then go back over with the #1 for the buildup and flow out of the piece.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
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Reply:Great idea for a thread. Thanks for posting up. Originally Posted by irish fixitThat brings up the discussion of flux. I prefer the Peterson brand myself but they make more than one kind.
Reply:Even at the price, i don't think I have gone full a full can of flux in years.  Although I use a lot less, just some on the rod.  Do most of you guys put it in the weld area as well?
Reply:Borax is so cheap, i sprinkle it all over the weld area as I heat the cast. If the flux flows well it usually means that the part where the flux covers is clean enough to braze. If there is an area where you do not want the brass to go, you can use Liver of sulfur as a resist. Mac
Reply:It always seemed like too much flux makes the bead more contaminated.  If I use precoated rod, I whack it on the table to knock about half of it off. I am not an expert at brazing, so I may be wrong.  With that much flux, does it all float to the top when you do it?
Reply:Tagged brazingThanks for the info Irish!"Where's Stick man????????" - 7A749"SHHHHHH!! I sent him over to snag that MIC-4 while tbone wasn't looking!" - duaneb55"I have bought a few of Tbone's things unlike Stick-Man who helps himself" - TozziWelding"Stick-man"
Reply:Originally Posted by KelvinGreat idea for a thread. Thanks for posting up.
Reply:Originally Posted by irish fixitThe more contaminated the flux is the harder it is to get off when you're done. So the more flux you put on there to dilute the contamination the easier it'll be to clean. If clean the flux breaks off like glass easily with a hammer.
Reply:Great post irish. I think I've been using to little flux. I will do some experimenting tomorrow.Trailblazer 302Hobart Stickmate AC/DCLincoln SP 135 TSmith torchSpoolmatic 30A
Reply:I like the paste style flux, it's easy to spread on a nice coat prior to heating. I think Zank uses about a quarter cup per lug.SqWave 200Millermatic 190Airco 200 ACHypertherm PM45Boice-Crane Band SawVictor O/A
Reply:Originally Posted by shortarcGreat post irish. I think I've been using to little flux. I will do some experimenting tomorrow.
Reply:I purchased some MG flux a while back, I get along with it on dirty cast better than the the Peterson. I will look to see what number it is when I get back in the shop next week. I have always preferred brazing to nickel welding where I can.
Reply:Did the old Peterson#3 have a fluorinated compound in it? Stuff cleaned good but ate anything up you had it in after drawing some moisture.I get the whole camera thing Irish. I was happy with my near 15 year old Panasonic miniDV until I saw Jody's stuff on "Tips & Tricks". So I got a lower end JVC 1080P mini cam recently and it was terrible with an arc weld. I finally got yanked off and spent some time with it last week and got it to behave. So I put my settings on Youtube here;I basically tuned the camera in manual mode while pointed to a florescent lamp until I could clearly see the fine edges of the tube. I set the camera to "manual", turned the shake function "off", backlight compensation "on", the scene setting to "daylight, brightness left on "auto" and last I used manual focus with the camera on a tripod. I think that's all I did & then taped a #10 gold coated shade to the camera & I'm happy with the result. I think for brazing or flame cutting a #3 to 5 shade would be needed.Here's a plan "B" braze with powder I did years back.Then there's plan "C" just friggin gas weld the stuff!And There's plan "C-minus" crack the sh!t while welding... Good thread, thanks!Matt
Reply:Originally Posted by Matt_MaguireDid the old Peterson#3 have a fluorinated compound in it? Stuff cleaned good but ate anything up you had it in after drawing some moisture.
Reply:Originally Posted by irish fixitI'm not sure what it had in it to be truthful. It was a two part mix and if any moisture got to it after mixing it turned into a rock. The #2 will definitely corrode the metal if left on after brazing. The #3 did a little bit but not as bad as the #2. I'm partial to Nikon since I still have some of my old good Nikkor lenses. They where one of the few things to survive the fire since they where in a hard case on the floor.  I checked several other options and there are a few out there but they run well over $1000 which is way beyond what I'm willing to spend.   I've also ordered some filters for it. Including a IR filter which I think might be important for this job even if it's expensive. I've got several ND filters and a variable version coming as well as UV filter. I'm hoping that combining them properly will help with getting the details I'm wanting. I've got a brazing job on a vise I just added to my newest welding table I need to do and I plan on trying to get a good video of fixing it.
Reply:Originally Posted by Matt_MaguireI must be thinking of a different flux, not a 2 partI shoulda flea bay'd my old Nikkor lenses years ago when they still sold adapters for them. Now you have to send them in & pay much the same as new... (my sh!ts pre-auto, all late 60's early 70's - rugged as h@ll though).Filters are good! And if you cant find one to screw on a Nikon or Hasselblad lense they don't exist.I s'pect you have as good a chance as any with the 5100. My Olympus wide-tele kinda SLR is 15MP and has the same problem with arcs so I'm kinda leaning to the software in the camera. The video mode is 640 x 480 at 60fps so I really didn't try to work it out as the miniDV was higher rez and I thought it did OK.If IR or UV was going to kill the sensors my Panasonic would have been dead years ago as I've many 100's of hours with it recording arcs for "record" to verify procedures asked for were done. I did always have good space and tele in to the subject with it though.Hoping it works well & waiting for the vids. Matt
Reply:Originally Posted by irish fixit  I've also ordered some filters for it. Including a IR filter which I think might be important for this job even if it's expensive. I've got several ND filters and a variable version coming as well as UV filter. I'm hoping that combining them properly will help with getting the details I'm wanting.
Reply:Originally Posted by Brent878Correct me if I am wrong but if you put two CP filters on then it would be like an adjustable ND filter.  I think this would be good for the welding as you could really be able to tweak the amount of light coming through with out spending a ton on ND and IR filters.    If not someone actually sells an adjustable ND filter but it was pretty expensive.  I got the idea after I already bought my ND filters so I never tried it out.
Reply:Originally Posted by irish fixitI do believe that two polarizing filters could be used that way. But I found a fairly cheap adjustable ND filter on Amazon which I ordered. The ND filter set was fairly cheap as well. A set of UV, Polarizing, and another filter was dirt cheap. However getting a good UV and IR blocking filter wasn't.   I got a Hoya rated to block anything except visible light and it was expensive but I think will prove one of the more important filters.
Reply:Wayne, glad to see you showing folks things that aren't done as much as they used to be. I thought for awhile brazing was becoming a lost art but lately I've been seeing more interest in it. I still do a lil' brazing on occasion when needed.                                         MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:Originally Posted by Brent878You don't really have to worry about UV.  From what I remember the censor's don't really pick up on UV like the film used to.  They are more senstive to IR but the camera usually has a IR filter near the censor.  I looked into years ago to take the built in IR filter out to take IR pics at night.  Only problem was I would need to run a IR lens filter all the time when not taking IR pics.  The IR filters were too expensive for me to get for each different lens size and it would have been cheaper to buy a dedicated body just for it.  I didn't want to take IR pics enough to have a seperate camera just for it.I would experiment with the UV and IR filters on and off, you may not need them and can return them to save some money.  Remember you only have to worry about what the camera can pick up.  And every extra piece of glass you shoot through degrades image quality.
Reply:Originally Posted by mla2ofusWayne, glad to see you showing folks things that aren't done as much as they used to be. I thought for awhile brazing was becoming a lost art but lately I've been seeing more interest in it. I still do a lil' brazing on occasion when needed.                                         Mike
Reply:Ok. Here's another attempt at a video. I'm still not happy with it but I think it's better. At least you can see some of the details.   I've still got to play with the filtering and settings.[ame]http://www.youtube.com/watch?v=Xz9ZC1SBQLY[/ame]Finally got it to embedLast edited by irish fixit; 04-18-2013 at 10:10 PM.Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:One trick I use when doing the delicate stuff, is moving the torch head back to help control the puddle. Closer to the work, hotter. Further back, colder. sometimes its not much movement,its all about watching the puddle and the flow. Works great on thin copper tubing. When doing alot of joints, move in close to get the heat in the piece, move out to braze and move on to the next. It works for me with silver.The vid looked great. You could see good definition in the flame.If you blow the flux away then your flame is too harsh.  Use a bigger tip and a soft flame and you will get enough heat with no noise, and it wont blow the flux away.  Mac
Reply:Originally Posted by cold1One trick I use when doing the delicate stuff, is moving the torch head back to help control the puddle. Closer to the work, hotter. Further back, colder. sometimes its not much movement,its all about watching the puddle and the flow. Works great on thin copper tubing. When doing alot of joints, move in close to get the heat in the piece, move out to braze and move on to the next. It works for me with silver.The vid looked great. You could see good definition in the flame.
Reply:Wayne,I was in no way trying to critique your work or technique. I hope it did not come across as that. Working the flame is just a trick I wanted to bring up for others that may be reading this thread.When I get guys coming through my shop, they have years of HVAC under their belt. Most have never used Oxy/fuel before nor have they ever brazed. They can solder well, but brazing is a new beast. Burned up piping, wrong alloy selection, boogers hanging off all joints, they just dont have a clue. One of the first things I tech them  is flame manipulation. Your skill with a torch shows all those years of expeirience. Your vids are great and very helpful, I can now use a cutting torch without getting melt back. I still have a long way to go before I can cut and make it look pretty.
Reply:Originally Posted by cold1Wayne,I was in no way trying to critique your work or technique. I hope it did not come across as that. Working the flame is just a trick I wanted to bring up for others that may be reading this thread.When I get guys coming through my shop, they have years of HVAC under their belt. Most have never used Oxy/fuel before nor have they ever brazed. They can solder well, but brazing is a new beast. Burned up piping, wrong alloy selection, boogers hanging off all joints, they just dont have a clue. One of the first things I tech them  is flame manipulation. Your skill with a torch shows all those years of expeirience. Your vids are great and very helpful, I can now use a cutting torch without getting melt back. I still have a long way to go before I can cut and make it look pretty.