Brazing questions

[Cdworks]

How does one braze in a forge? I get the gist of brazing, but have never done it before. What metals can you use for brazing mild steel( brass or copper?)? I'm still perfecting my forge welding technique ( got three poor welds under my belt) and would like to have an alternative to it.

I could probably go try it and figure it out but that sounds fraught with failures.

Some other questions I have. What flux? Will borax work for brazing?

Searched YouTube and ifi and couldn't find anything. Gonna search some more.

Thanks in Advance!

[Frank Turley]

I responded to this recently on this forum, q.v., under the heading, VISES, "Fixing a Small Leg Vise..." I wouldn't say forge brazing is necessarily easier than forge welding. It depends on the shape of the objects and the care with which they are assembled. Brazing is a hard soldering technique done above 1,000F. The ferrous parts to be brazed can be united with copper, brass, or silver solder. Borax is used as flux.

[Charles R. Stevens]

What kind of forge? Gas, solid fuel or?
The basics of braising, heat the parts to cherry (for steel) brush clean of scale , add brass or copper place the parts back on the heat and wait for the brass or copper to melt. In practice it's usually best to clean the parts very well cold, put a thin bit of copper or brass between the parts and wire them together with stainless wire. Flux to exclude air, I use a commercial flux but any of the home brew will work. Again heat until the brass/ copper flows.

Master turley is faster on the keyboard and a much letter teacher than I am.

[Cdworks]

Gas forge. Thanks for the information.

[Jack Evers]

In my farrier practice, I often resort to brazing when the ambient temps are low as is my bottle level and I just can't get welding heats. I use copper (sometimes wire, often flattened tubing) since it's melting point - 1900 F - is much higher than braze rod. prepare the joint, add flux (often borax), heat in forge while watching for it to melt. Pull out and press (not hit) with a hammer face - the hammer just cools it quickly. With a copper braze it can be reheated to a red forging temp.

[Cdworks]

One thing i guess is probably important is to make sure the item you are brazing is shaped to fit. Thanks for the advice! I'll give it a try this evening.

[John McPherson]

In brazing and soldering, the better the fit-up and the tighter the gap = the better the capillary action and the stronger the joint. You want the molten metal to flow between the two pieces being connected.

[David Gaddis]

I have brazed a whole lot years ago. Then a few weekes ago I showed one of our younger smiths the technique as we repaired transmission supports for a Champion Blower. I told him that he was not likely to ever see that process ever done again in his life.

 

Now you have excited me about using copper, and then brazing to making a repair joint. Perhaps I miunderstood your operation.

 

Many of us here would be delighted to see some pics of such a weld...if possible. That could make a delightful demo to our forge council too.

Please try to do some pics...even if on something insignificant.

 

Thanks in advance.

 

David gaddis

 

 

Carry on

[Cdworks]

Finally found a good source.

 

http://www.youtube.com/watch?v=m678-clpbjw

 

I have plenty of copper wire around the shop from when i wired the shop! Definitely giving this a try tonight.

 

Thanks again!

[Frank Turley]

Well, yes no and maybe. The torch method is brazing, but it is not like forge brazing. No built-up bead is laid in forge brazing. In my earlier post, I said "q.v." meaning "which see." I was referring to my other forum post which I thought was fairly thorough in its explanation. If the two pieces are held together, possibly clamped, and copper placed adjacent to the joint, when the copper melts and runs, it should go between the surfaces by a process of "wetting" (capillary attraction). The pieces are then pressed together to aid in this action. The quick water quench will cause cuprous oxides to pop to the surface, some flaky looking, By immediately wire brushing, this cleans much of the surface. On a well made forge braze, there will be a thin line of copper showing at the joint, barely visible. There may be a little copper spillage, but it could be measured in the thousandths of an inch, It is negligible.

 

Shown is what we call a "jar calk," a low calk to add a little traction to the shoe.

[Mainely,Bob]

As others have said brazing is a process where a filler metal that melts at a heat below the melting point of either of the two pieces being joined flows between the pieces and bonds them together once cooled. It works like soldering but at a higher temperature. There are filler materials available that melt at different temps so an experienced hand can put together complicated assemblies using multiple heats without worrying too much about remelting the prior joints and having parts fall off.

    It has been my experience that with torch brazing you can control the flow of filler metal by directing it with heat. When doing forge or furnace brazing you rely on the prep and flux to control the flow of the filler metal. Anything that was not cleaned and/or fluxed will not accept the filler metal. You can also get brazing paste that combines both powdered filler and flux to brush on the joint prior to assembly but the use of this type of product requires a very close, high quality fit.

    Soldering, silver soldering, both low and high temp brazing and welding all have their appropriate applications. Soldering and brazing really come in handy when joining dissimilar materials that can`t effectively be joined by methods such as welding.

   I think you`ll find it time well spent to study up on all these different processes and learn both how, why and where each one is most appropriate.Many times knowing things like this made all the difference between me or someone else either spending or receiving a rather sizable amount of money.

[chichi]

I will describe how I forge braze  powder pan(where blackpowder is held) to a lock plate on a flintlock .

As described above, the pieces need to be in position while in the fire. I forge the pan, file the mating surface flat and shiny. I then drill a 1/8 hole in the lock plate where I want the pan. I also drill a 1/8 hole in the pan and pin the two pieces together with 1/8 rod. (I sometimes use two pins). The parts are held securely and in close fit. I put the plate with the pinned pan in the forge and heat. Once it gets red, I add flux and then keep up the heat and touch some brazing rod to the joint. The rod melts quickly and the brass/bronze runs into the joint. I stop the blower and let the piece cool a little. I then remove and quench. The joint is really strong. I did a test piece and beat the pan and I couldnt beat it from the lock plate.

Instead of rod, I could use little pieces of brazing rod in the joint and it would work as well. This is easier than forging the pan or trying to weld a pan to the plate and it is historically correct. It is a good skill. I have done a few other things using this metod. Give it a try and good luck.

[GNJC]

Copper has been advocated, very interesting.

 

I've got a few old (mid to late Eighteenth Century) pieces of domestic metalware that show evidence of brazing to repair / join wrought iron and, in one instance, steel. So far as I can tell, these all have brass as the 'sticking' medium. I have not yet seen copper used elsewhere either, but maybe this is a local preference - I am in the UK and techniques vary from county to county.

 

So, and I am assuming that the smiths back then knew their business and didn't waste time / money on work that was going to come back with a complaint attached, the question I want to ask is: what is the advantage of brass over copper or silver for these joins?

 

Thanks in advance for advice on this, because in the near future I will need to braze a couple of joins and I want to do things effectively as well as authentically.

[Cdworks]

would brazing be the choice of connection for say scrolls and such in decorative work?

[ThomasPowers]

the old books mention filing "spelter" (brass) to get materials for brazing.  The advantage of brass over copper is that it melts at a lower temp and was cheaper.

 

Forge brazing of scrolls would be a pain to get them held and positioned correctly while heating.  If you are torch brazing, you are pretty much a half step from torch welding why not do that and avoid galvanic corrosion possibilities?

 

Last piece I forge brazed was a ladle cut to a forged handle---didn't have access to a drill to rivet and was very thin stock for the cup and so forge welding would be a bit iffy.  Biggest issue I had was the charcoal burning out underneath it shifting the workpieces.  Got er done though and so far it's held---only 15 years on it as the water ladle and coal scoop for my forge.

 

Borax makes a fine flux for brazing and is the major constituent of commercial brazing fluxes.

[Jack Evers]

Copper has been advocated, very interesting.

 

I've got a few old (mid to late Eighteenth Century) pieces of domestic metalware that show evidence of brazing to repair / join wrought iron and, in one instance, steel. So far as I can tell, these all have brass as the 'sticking' medium. I have not yet seen copper used elsewhere either, but maybe this is a local preference - I am in the UK and techniques vary from county to county.

 

So, and I am assuming that the smiths back then knew their business and didn't waste time / money on work that was going to come back with a complaint attached, the question I want to ask is: what is the advantage of brass over copper or silver for these joins?

 

Thanks in advance for advice on this, because in the near future I will need to braze a couple of joins and I want to do things effectively as well as authentically.

I can't speak for the old guys, but cost, availability and suitability all would play a part. It really doesn't take much, so cost might be minor.Two hundred years ago, I would guess that brass may have been more readily available than copper, while today, at least for me, there's always some copper wire or tubing around the shop and seldom any scrap brass in reasonable dimension. In addition for my shoe making, I may need to do some forging (shaping) after the joint is brazed. Copper has a bit higher melting point and makes this easier for me than brazing rod, which is the only brass that I've tried.

[ThomasPowers]

think on the old term for copper brazing: "penny weld"  though US cents were an alloy and not pure copper even before they became zinc filled!

[Bentiron1946]

I have done it a few times in a solid fuel forge, no need for a gas forge. It has been done far long in charcoal and coal forges than gas so it ain't all that advantageous to use a gas forge and if you going gas why not just use your gas torch? A good fit of parts is necessary and no brazing is not a gap filler, it is and never was meant to be a gap filler. If you have that big a gap do some more work on the fit, that's files are made for, refining the fit, not just turning into knives. The method Thomas mentioned using the filings form good brass stock works better than just laying a piece of brass wire along the join, I mixed mine up in a thick paste with the flux and put it all along the seam, this seem to work the best for me and then I brought it up to temperature. My first few failed but after a couple of more I was doing them right along. A couple of years ago on the Wood Wright he had a fellow making Colonial door locks and he was brazing them together, it was a pretty good show, you maybe able to find it on their web site.

[Jack Evers]

think on the old term for copper brazing: "penny weld"  though US cents were an alloy and not pure copper even before they became zinc filled!

 

 

I believe 1981 and before pennies could be used to braze - I've done it. After 1981, pennies are mostly zinc. Fellow that taught me was asked what he charged for a pair of bar shoes. Twenty dollars and 2 cents with the 2 cents up front and in cash. Been a long time, Thomas, since I've thought of of the penny weld.

[JimsShip]

^{Excellent thread.
Always a good day when you learn something new!}

[Cdworks]

didnt get to try it yesterday.

 

Thanks guys for the advice.

[BorisTheSpider]

Excellent thread, guys! I have an old lawn chair (you know, not one of the cheapy, folding deals) with some damage to one of the legs. It's like a rolled sheet of steel -- not a tube; more like a flat section with a tube on each side, if memory serves me. Wonder if I can fill the void a bit with some spare sheet, and braze it all together. No reason I can't try anyhow. Now off to watch some videos.

[JandJArsenal]

I have a tendency to mix brass powder edit into my brazing powder. The outcome after a good heat is more or less a brass weld that the braze drew into any minute spacing between the metals. The cautious part is overheating when you get ready to finish a solid forge weld of the metals together. The brass can, and likely will, leak out onto your anvil with hammer strikes.

This is easily cleaned off with a torch and a steel wire brush. 

[ThomasPowers]

By "brazing powder" do you mean brazing flux? Brazing powder already is a mix of brass and flux.  Forge Brazing was called a penny weld back in the 19th century as you could use a penny for the brass. (US pennies are not pure copper.)  It should not be heated up to glowing after a braze is done and so forge brazing is usually the last hot job done on an area.

I recently had a fitting that was loose so I forge brazed it on the backside to hold it stationary.  It's on my wall right now.  I have an old postvise where the screwbox was built up with forge brazing out of a bunch of pieces and had the screw thread forge brazed into the tube.  Frank Turley told me he thought it was "pre-1800" and probably made it to America with an immigrating craftsman's tools.

I also have used it to fasten the cup to a handle to make a larger ladle without riveting.

It's another technique used by old time smiths and often not known by modern hobby smiths.