Brass Brazing
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Thread: Brass Brazing

  1. #1
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    Brass Brazing

    Hello everyone,
    ive got some questions about brazing brass. A friend of mine has and old machine that has a collar around a handle that has broken. the collar is probably 2 1/2" od and its about 3/8" thick. its totally broken in half. ive done a little brazing but not on brass and i dont currently have access to a tig rig.
    first question is - will brazing be strong enough? second - can you do multi pass brazing? Im sure i need to bevel the pieces to get a full pen weld but i dont know how to build it back up. maybe its pretty easy but ive just never done it.
    any suggestions would really be appreciated and thanks in advance..

  2. #2
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    Re: Brass Brazing

    Just to clarify, you mean the broken part is brass and not that you are brazing with LFB rod, correct? With proper heat control and proper prep, you can draw silver braze through the 3/8" thickness brass. 56% silver rod will flow easier than 45% or 50N rod, and it's liquidous at about 1200*F vs 1370*F for 45%, which is important because brass starts to melt at about 1650*F. But I can't comment on whether it will be strong enough considering the original part broke.
    Last edited by zank; 05-23-2012 at 06:35 PM.

  3. #3
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    Re: Brass Brazing

    the piece thats broken in two is brass but to be honest most of what you just said i dont know anything about. i bought brazing rod and flux, i have a torch set up and maybe not even enough knowledge to get this done. it sounds like what you are saying would involve not beveling the edges and just drawing braze through the crack to fuse it, is that correct? im a structural welder and am so used to carbon steel that i may be looking at all of this the wrong way.

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    Re: Brass Brazing

    and yea, this is a really old bread cutting machine and this pretty big piece of brass broke in half, that says to me that there is a lot of stress being put on this part. i believe with a little help i can figure out the brazing part but if its just going to break again i wont attempt to do the work.

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    Re: Brass Brazing

    He was suggesting that silver soldering would be better, and I agree. Brass contains zinc which vaporizes when brass is heated to the melting point. While doing so, it causes bubbles, changes the composition of the base metal, and makes welding hard. The silver solder is pulled into a joint by capillary action, forms a very strong bond, and doesn't require the high temperatures brazing does. An appropriate silver soldering flux, mixed with water or ethanol, is also easy to get into the joint before starting the heating.

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    Re: Brass Brazing

    Quote Originally Posted by jonnyoh72 View Post
    and yea, this is a really old bread cutting machine and this pretty big piece of brass broke in half, that says to me that there is a lot of stress being put on this part. i believe with a little help i can figure out the brazing part but if its just going to break again i wont attempt to do the work.
    Some brass gets brittle with age, often if it contains a little lead. Some old zinc alloys turned to powder when aged a few dozen years, just like slightly impure zinc does at low temperatures.

  7. #7
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    Re: Brass Brazing

    jonnyoh72 when you braze brass, your filler rod can't be the brass or bronze brazing rod you normally use for brazing steel. Why not? Brass work piece and bronze filler rod - the melting points are too close - that makes the process more like welding. You run a real risk of turning the work piece into a molten blob of brass.

    What you need is a "brazing" rod that that melts at a lower temperature - like the silver solder that was suggested.
    I hope that helps...
    Rick V

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  8. #8
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    Re: Brass Brazing

    Got a lathe? Turn a new part!

    No lathe? Send complete dimensions with drawings and $25 with return addresss to me and I will make and return a new part.

    -Mondo

    PS: You could use a drill press for this.... 3/8 x 2-1/2 flat brass bar at least 2-1/2 long. Clamp to table, use hole saw of appropriate size to cut ID, then use 2-5/8 hole saw to cut outer diameter. A little file and buff... Voila!

    -Mondo
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    Re: Brass Brazing

    lots of good info, thanks guys. ill try to respond to all of it...
    first off what the welding supply store recommended was this LFB-FC rod. i probably wasnt too clear with them on exactly what i was doing so maybe its the wrong filler. as i was driving home i was thinking "how would you do multiple passes if the filler and the base both have to be molten to tie in?" thats why i started this thread, thinking about filling up a crack that id beveled with this process wasnt making much sense.
    it seems almost too easy to be true that i could just fit the two pieces back together and use silver solder to rejoin them and have any strength at all but i sure could be wrong!
    as far as a lathe, i do not have one. also the piece has a gear on one side that would make it hard to replicate.
    ive been welding for a quite a while and just bought my first engine drive (Miller Big 40) and am slowly getting everything together to have a complete rig. Bought torch bottles just for this job (ouch!) and now its looking like i shouldve bought the rest of the stuff for a tig rig instead. My name is starting to get out in town and people are starting to call for work and i dont want to do this job and screw it up although theyve offered me alot of money because they love this old machine.
    i might be able to scrape up the money for the rest of what i need to get a tig set going, would that be the best way to do this?

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    Re: Brass Brazing

    and actually the real question has become solder or tig?

  11. #11
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    Re: Brass Brazing

    Quote Originally Posted by jonnyoh72 View Post
    and actually the real question has become solder or tig?
    since you dont have access to tig, the only solution is try silver solder and see if its strong enough. that probably has less of a chance of destroying the part than tig does..
    tell them in advance its an experimental area due to the nature of brass..
    Last edited by weldbead; 05-24-2012 at 04:18 AM.

  12. #12
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    Re: Brass Brazing

    Quote Originally Posted by jonnyoh72 View Post
    ...second - can you do multi pass brazing?
    In my experience... No. The previously brazed material in close proximity to the heat will melt - and you have a slumped mess. This is a major advantage of welding; you can do multiple passes.

    Quote Originally Posted by jonnyoh72 View Post
    ... "how would you do multiple passes if the filler and the base both have to be molten to tie in?" thats why i started this thread, thinking about filling up a crack that id beveled with this process wasnt making much sense.
    it seems almost too easy to be true that i could just fit the two pieces back together and use silver solder to rejoin them and have any strength at all but i sure could be wrong!
    You have good reason to be worried. You can't do multiple passes. The only way I could see "filling up a crack that id beveled with this process" would be if the perimeter was wrapped with thin sheet brass to retain the molten silver solder as it solidified. Then you are almost making a brass mold and casting with silver solder - albeit with adhesion between the wall of the brass 'mold' and the silver solder.
    Rick V

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    Re: Brass Brazing

    First it is hard to give any advice, with out knowing what I am talking about. But if the part is brass, and not some other alloy, it will be very critical of to much heat. I would use acetylene and oxygen and silver solder the part. If it is very clean, well fluxed and the temperature is just right it will be almost as strong as original. This is assuming that you have not removed any of the material with a grinder or sander or such.

    Silver solder is only used in places where you just have a very tight crack to fill, as it will run all the way through a very tight crack but will not work well to fill a space like a beveled joint. Personally I hate this kind of job and I have done many of them. It might be interesting to look up bronze or brass in Wikipedia. . Mac

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    Re: Brass Brazing

    Quote Originally Posted by Tool Maker View Post
    First it is hard to give any advice, with out knowing what I am talking about. But if the part is brass, and not some other alloy, it will be very critical of to much heat. I would use acetylene and oxygen and silver solder the part. If it is very clean, well fluxed and the temperature is just right it will be almost as strong as original. This is assuming that you have not removed any of the material with a grinder or sander or such.

    Silver solder is only used in places where you just have a very tight crack to fill, as it will run all the way through a very tight crack but will not work well to fill a space like a beveled joint. Personally I hate this kind of job and I have done many of them. It might be interesting to look up bronze or brass in Wikipedia. . Mac
    I agree with the first statement above; pictures or a diagram and a bit more detail would be of good value with a question like this one. For example, how does the brass collar fit on the inner piece? Is it a slip fit or required to be tight? Did stress from a restrained fit, together with increased brittleness over time (as mentioned earlier) lead to the break?

    As I said in an earlier post, braze welding should not be considered IMHO. The silver solders are very strong and come in a number of variants; here is a list of All-State alloys
    Another alloy with a strength of up to 85 ksa is this All-State Nickel-Silver.

    If you have gaps to fill, look at Sil-Fos 15. I don't know it's strength, but also don't know the strength needs of your part or why it broke. Here are the other Sil-Fos alloys.

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    Re: Brass Brazing

    thanks guys! theres alot of good info im going to have to go over here.
    i have decided to turn down the job, im just getting started with this little welding business and would rather say no to a job than break something that i cannot fix or fix something that will just break again. I love a challenge but not one like that.
    its funny how often when i start to say to myself "hey, ive gotten to be a pretty good welder" that something like this comes along and helps me to remember how much i still have to learn.
    guess whos going to by buying junk brass, breaking it and learning how to stick it back together? This Guy!
    thanks again everyone!

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    Re: Brass Brazing

    Quote Originally Posted by jonnyoh72 View Post
    thanks guys! theres alot of good info im going to have to go over here.
    i have decided to turn down the job, im just getting started with this little welding business and would rather say no to a job than break something that i cannot fix or fix something that will just break again. I love a challenge but not one like that.
    its funny how often when i start to say to myself "hey, ive gotten to be a pretty good welder" that something like this comes along and helps me to remember how much i still have to learn.
    guess whos going to by buying junk brass, breaking it and learning how to stick it back together? This Guy!
    thanks again everyone!
    Just to add a little more meaning to this thread, you might ask your friend to give you some pictures of the part so you could post them here. He might even get lucky and have someone here decide to do the repairs for him. We do, of course, need a good picture of the whole machine too, 'cause some of us like old machinery---or rather, just about any old stuff.

  17. #17
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    Re: Brass Brazing

    I have been a student of the welding arts for 55 years, trying to weld what has to be with whatever, and mostly oxy/ac process for the small hard to manage things.
    A lot of brazing experience so please let me state that multi pass brazing is not difficult in fact common practice.It's all a matter of controling the heat of the molten puddle/deposit.
    If the work piece were in danger of dissolving into a molten blob, brazing wouldn't be so versitile for buildup.
    We commonly buildup cast iron or steel heavily with bronze rod. Once the face of the parent metal is "tinned" or "buttered" with fluxed bronze then the succeeding metal can be added without flux and is just a bronze weld--built up where and as much as you feel like.
    I have seen brazed bronze base material but can't remember personally doing it--have however built up quite thick pads on cast iron to allow bolt pattern changes by redrilling.
    One thing sure, don't consider the common "brass" bushing of the oilite or sintered metal type for weld or braze because the base metal is porous with the purpose of retaining oil.
    One thing sure, the brazing should be attempted by a proficient Oxy/acetyline weldor.
    If it's the first time, find a piece of similar material to practice on.If overheating is expected a hazard then think of ways to arrange a heat sink like partial submerging in water or clamping selectively to a piece of copper or aluminum.
    I think it can be brazed with good results.

  18. #18
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    Re: Brass Brazing

    For some information on oxy/acetyline torch use including great information on brazing, braze welding, and many others, search for :euweboxyhandbook
    The handbook has much RELIABLE and proven information for the torch user.

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    Re: Brass Brazing

    Quote Originally Posted by Oldiron2 View Post
    Just to add a little more meaning to this thread, you might ask your friend to give you some pictures of the part so you could post them here. He might even get lucky and have someone here decide to do the repairs for him. We do, of course, need a good picture of the whole machine too, 'cause some of us like old machinery---or rather, just about any old stuff.
    This old tool is a bread cutter in a really busy kitchen. they use the thing everyday and now have it rigged to work. ill try to get back in there to take pics.

  20. #20
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    Re: Brass Brazing

    Quote Originally Posted by enginenut View Post
    For some information on oxy/acetyline torch use including great information on brazing, braze welding, and many others, search for :euweboxyhandbook
    The handbook has much RELIABLE and proven information for the torch user.
    thanks man. ive been welding for about 15 years but 99.9% of that was structural on carbon steel. love to learn stuff, guess its time to dive into brazing!

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    Re: Brass Brazing

    This is also worth checking out.

    http://www.brazingbook.com/

  22. #22
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    Re: Brass Brazing

    Just to add that Lincoln's Bible has a good section on joining copper alloys.

    Brass has it's own set of challenges. As has been pointed out, brass can be of many different compositions.

    Using a tig torch on brass can present a whole "baileywick" of challenges. Unless you're "really experienced" you're most likely going to "burn off" the zinc before you achieve a molten state. Ox/ace and silver solder is my "go to" when dealing with brass.
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  23. #23
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    Re: Brass Brazing

    Quote Originally Posted by jonnyoh72 View Post
    ...as far as a lathe, i do not have one. also the piece has a gear on one side that would make it hard to replicate...
    Gears can be cut on the lathe. Can you post some photos of the broken part?

    -Mondo
    Member, AWS
    Lincoln ProMIG 140
    Lincoln AC Tombstone
    Craftsman Lathe 12 x 24 c1935
    Craftsman Commercial Lathe 12 x 36 c1970
    - - -
    Ask for a wrench and someone will offer you a grinder.
    I'll just keep on keepin' on.

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