Brazing advice needed!!

[pelallito]

Hello,
I was searching for information on brazing and saw that acid and pickling baths were mentioned. Can some one give me tell me about both.
The acid was used as part of cleaning prior to brazing, and the pickle for post brazing clean up.
I attempted to use some brazing rod yesterday with less than spectacular results.

I posted this on the Atlas mill and shaper page. I am in the process of making a new eccentric lever for the mill. This is attempt 3. The previous attempts
were ruined because my piece of scrap brass had air pockets that I did not see until turning number 2.

At the moment, I am not sure of where number 3 is standing.
I cleaned all surfaces carefully, screwed the handle in and started brazing the
piece.
I put it on top of a piece of steel that I had on top of a single burner propane
camp stove. I preheated the piece, and then started attempting to apply the
brazing rod as I played my O/A torch on it. I finally got it to flow and put it
on the piece. When I thought that I had put enough on outside surface, I flipped
the piece and started on the inside face.
The heat immediately melted the thin wall of the 5/16Th" inch hole. I had to
rebuild it! As you can imagine, I was thinking some dark thoughts at that point.
I was successful in building it up and I brazed around the handle.
After turning off my torch, I decided to take a good look at the piece to see if
I needed to apply any more braze to it.
The piece slipped out of the vice where I had placed it and fell to the floor.
Since it was hot, I did not try to catch it. When I looked down, it was broken
in two pieces.
It apparently landed on the handle, and it broke just above where the transition
of 1/4"-20 TPI finished and the 5/16Th bottom of the tapered handle.
MORE DARK THOUGHTS.
The next handle wont be made of brass!!! Probably SS.
I put it into the drill press after it cooled a little and found center on the
broken stub, put a small end mill in the chuck and made a small flat spot that I
could drill into. I drilled and retapped the hole.
I then started cleaning the piece of the flux and reshaping it.
I need to make a long pilot for my 5/16Th" counterbore and will try to re cut the
hole. The stepped hole seems to be fine in the 3/16Th and 1/4 inch parts.
I then quite for the night, I had done enough damage for one day!
Thanks for listening,
Fred

I think that part of my problem was that the brazing rod was too thick, and required a lot of heat.
Any advice happily accepted! :-[,

Thanks,
Fred

 

[f350ca]

Fred
Correct me if Im misunderstanding your project, but sounds like your brazing brass parts. If so your no longer brazing but welding as the filler is the same as the parent metal. The trick is brass transfers heat so well, the hole part is close to melting temperature when you get the joint hot enough to get the rod to flow.
Could you use one of the silver solders that melt below the melting temp of your brass parts. Gives you a little room to play with.

Greg

 

[Entropy455]

Agree. You need to select a brazing rod that has a lower melting temperature than the metals you’re joining. I.E. trying to join brass components together using brass brazing rod is more of a welding process. The the brazing flux would only get in the way, and the results will be unsatisfactory at best.

If you’re brazing brass components together, a silver brazing rod would be a good choice. Cadmium silver braze has a lower melting temperature than cadmium free silver, however you must be VERY careful not to breath the fumes from cad-based silver. (Generally you do not want to breath any brazing fumes.. . . )

If your joint does not require a lot of strength, lead-tin solder will work well, and the joint can be made at significantly lower temperatures than that of silver brazing rod.

Note: the difference between brazing and soldering is the temperature in which the filler material melts. It is generally accepted that when your filler material melts at greater than 800 degrees F, the process is considered brazing. When the filler material melts at 800 degrees F or less, the process is considered soldering. I often hear silver brazing rod referred to as silver solder, which is incorrect. If it melts at 1300 degrees F, it certainly is not solder. On that note, there is such a thing as silver solder. It's used in high end electronics – typically high end audio. It's a lead-tin based solder with trace amounts of silver added to increase electrical conductivity. Real silver solder is extremely rare, overly expensive, and will likely not be found at any welding store in the world.

It is difficult to make proper brazed joints with brass and/or silver brazing rod, using a propane torch only. You really need an oxy-acetylene, oxy-propane, oxy-map, oxy-natural gas, etc (key word being oxy). Regular fuel-air torches are not hot enough, and cannot significantly and rapidly raise the temperature of the joint. Instead the heat will flow deep into the part, often resulting in the brazing material uncontrollably wetting out all over the work piece.

 

[Blogwitch]

It is difficult to make proper brazed joints with brass and/or silver brazing rod, using a propane torch only.

I'll just concentrate on the silver part of that quote.

I must go back over forty years and check that all my joints are correctly silver brazed (we call it silver soldering in the UK), as all we use are propane and butane torches with NO oxy. The only time you would use oxygen is when you are soldering up very large pieces, such as a very large boiler where you need to get a lot of heat into it so the solder will flow.

To get back to the initial problem, it has already been stated that you shouldn't braze up with brass rods, the melting temperature is just too close together, but silver solder would have made a perfect job of it.

John

 

[tel]

Yes indeed - perhaps 80% of my silver soldering is done with propane.

Brazing and silver soldering are two separate and distinct processes and the materials and procedures for the one, will not mingle with the other!

 

[Entropy455]

Bogstandard, you have taken my comments out of context. I never said that you couldn’t braze joints with a fuel-air torch.

To add further clarification - when accomplishing a socket-type brazed piping joint, or joining boiler tubes to a tube sheet, it is desirable to have the brazing material wet out and readily flow over the work piece - in which case a fuel-air torch could be used.

If you are attempting to join two “widgets” together, using a fillet joint for example – you are unlikely going to obtain a pretty and uniform fillet bead along the joint (one that looks like a weld), if you blast the parts with a fuel-air torch. The filler metal will tend to wet out all over the work piece, leaving a very thin and weak fillet at best.

The overall heat input into the part is minimized when you have a very hot and localized heat source. Oxy-fuel torches make it easier to contain the filler material within the joint (to create actual fillet beads – like they’ve been made with a TIG torch in a welding process.)

For this reason, oxy-fuel torches are MUCH better suited for joining “parts” together.

There is little difference between bronze brazing, silver brazing, and soldering – other than the heat input and flux requirements.

 

[tel]

There is little difference between bronze brazing, silver brazing, and soldering – other than the heat input and flux requirements.

........ and filler material, and procedure, and application and .....

 

[pelallito]

Guys,
Thanks for all of the replies and advice. I should have asked you before I did the brazing/welding ( whatever I did). :-[
I am going to try to save the piece, but it might become another practice piece.
I don't like how it looks right now.
I did not just want to attach the piece, but also build it up so that I could change the shape.
The attachment, is the plan that I am working from.
Can you help me about the acid bath and pickle mix? ???
Thanks again,
Fred

View attachment Atlas%20Back%20Gear%20Lever.pdf

 

[tel]

OK! First thing, make sure of just what your filler rod is 45% Silver silver solder for preference, with the appropriate flux.

Flux well and then apply gentle heat with the outer envelope of your flame - NOT the inner blue tip - waggle it around so that the whole job hears more or less evenly.

Watch the flux - first it will dry as the water is driven out of it, then it will melt and turn from a whitish powder to a shiny fluid - NOW apply your stick to the joint area with the flame somewhere else - the latent heat in the job should flash the solder, NOW bring the flame around the job to make sure it is soldered right around - the molten metal will follow the flame.

Remove heat, let it cool to black, dump it in the pickle - it should only need a few minutes in there, remove from pickle (with tongs) and give it a good wash under the tap - scrubbing with an old toothbrush (or your good one if that's all you have)

Job done.

You can do it a lot quicker than you can read this.

 

[pelallito]

Tel,
Thanks for the help.
Exactly what is the pickle?
Fred

PS I suddenly thought of this- I am using two pieces of bearing brass, one pressed into the other.
I wondered if either is oil impregnated?? That might have something to do with the problems I had.

 

[tel]

Yes, oil will give to problems - the main trick to silver soldering is have thew job scrupulously clean.

Basically pickle is just a dilute acid bath use to remove flux residue and some of the oxidisation from the heating process. There are a lot of different things you can use, but citric acid is popular, safe and readily available (supermarket). Personally, I use about a 10% solution of phosphoric acid (food grade) - but that is mainly because I have a couple of hundred litres of the stuff on hand!

 

[pelallito]

Tel,
This sounded like a very good reason-
Personally, I use about a 10% solution of phosphoric acid (food grade) - but that is mainly because I have a couple of hundred litres of the stuff on hand!
The citric acid you mentioned. are you thinking of lemon or lime juice?
Sorry to bother you with so many questions!
Thanks,
Fred

 

[tel]

The citric acid comes in powder form Fred - usually in the baking or preserving section of your friendly local .....

 

[Blogwitch]

I have mentioned this a few times now, and will most probably mention it again sometime in the future.

For citric acid pickle.

What you require is what is called a saturated solution, and is very easy to do indeed.

Get yourself a plastic bucket with a sealing lid, I found popcorn tubs ideal, they are about half a gallon.

Fill up with warm water to about 3/4 full (or 1/4 empty).

Whilst stirring continuously, add the white crystal powder until it gets to a state where no more will dissolve in the solution. Don't worry if there are some undissolved crystals in the bottom.

Job done, now wasn't that easy.

A few pointers.

I keep mine until it doesn't work any more, that could be over a year or more, it goes thru colour stages, from yellow to green to almost black. The more you use it, the quicker it will stop working.
With the flux I use (Tenacity), I have found that somewhere between 1/2 to an hour soak is usually plenty long enough to clean the parts up in a new solution, some fluxes are harder and might require an overnight soak before it loosens off and can be easily removed with a wire brush.
Don't be worried about leaving it in too long, a couple of weeks should do your parts no harm unless there is ferrous material amongst your assembly, that will start to rust away if left too long..

Some people add a small spoonful of household bleach to stop algae growing in the solution over time. I don't bother, but I do start to wear protective gloves when the things growing in there start to look like they will bite. I have even had like small sherry florets growing on the surface after a fair time, but it still did the cleaning job OK.


John

 

[pelallito]

Tel and Bogs,
Thank you both for the explanation. I will look in the supermarket tomorrow.
Before I read this, I mixed key lime juice and water and left the piece in it. I think that I wasted some good lime juice! :big:
I might be able to save the piece. I made a two step extra long pilot for my 5/16th" counterbore, and recut the part of the hole that melted away.
After some TLC and cussing, the locking pin slides in and out.
Thanks again,
Fred

 

[Pappy Frank]

I may be late comming in on this, but there is a product that refrigeration men use that is called Sil-Fos, I am sure that is a trade name, but clones are available under other names. I use it for anything that requires silver solder. It runs cool, and if you have your brass clean it requires no flux, and thus no pickle afterwards. I get it at a refrigeration supply store, and have also gotten it at a welding store. I have some real silver solder here but will never go back to it after using the Sil-Fos. It can be used with a propane torch, but runs better with the oxy fuel. You use it just like silver solder and as I mentioned if it is clean, no flux.

Pappy Frank

 

[sunworksco]

http://www.silfos.com/index.html

 

[Jasonb]

PS I suddenly thought of this- I am using two pieces of bearing brass, one pressed into the other.
I wondered if either is oil impregnated?? That might have something to do with the problems I had.

You don't want a press fit when silver soldering, you need a thou or two so the solder can flow into the joint. If using a press fit all that will happen is you will get a fillet of the filler material around the edge and no penitration.

This is another reason for using just propane for silversoldering as the whole of the parts are heated and the solder will flow through the joint, the risk with using a hotter flame is that the filler will just form on the outside resulting in a weak joint.

J

 

[lee9966]

Any opinions on brass brazing unknown stainless steel? If it would work at all, what flux would be needed, just what is on the brazing rod?

I asked this here since the brazing professionals are watching

Lee

 

[sunworksco]

Try this link for a very good "Hot-To" .

http://www.ehow.com/how_6144307_silver-solder-stainless-steel.html

http://www.silfos.com/htmdocs/product_support/alloy_selection_guide.html