silver solder?

[Aydelott]

I have made my crank in 3 pieces I was going to silver solder it but I got oil on it an my instructor said in his experience if you get oil on it the silver solder wont stick ive tried red lock tight an epoxy nether will hold is there some type of acid or something that can get the oil off? My boss just tought me to braze with brass rod will that hold. Please help IM so close to having this thing done I have about 650 hours in it I think I took on a little more then I could handle for my first engine thanks

 

[hacklordsniper]

I use alcohol or acetone for degreasing

 

[Aydelott]

does any one know what type of silver solder an flux i should get

 

[rkepler]

does any one know what type of silver solder an flux i should get

For general use with brass, bronze and steel I tend to use 'white' flux such as McMaster # 7693A1. Clean things with acetone or any other clean distillate (not something from the degreaser tank) then wipe with clean alcohol (denatured, not "rubbing" alcohol that will have something in it). Put the flux on everything that you want wet, even it it's going to be touching something else with flux. Put it together, wipe off the excess flux and get ready to braze things.

There are multiple silver brazes available with different capabilities. For occasional home use I'd suggest a braze with cadmium - it wets and flows better. It's not a good choice for someone using it every day, but once in a while won't build up cad lavels in your body. Then you want to compare tight joint vs. fill - the latter will leave a fillet around a joint, the former won't. The latter won't go into a .002" gap, the former will. I choose each based on the joint type. (I just looked at the prices, you might be best served by scrounging some...) I cut small bits of wire and place it on the joint, when heating I use a little wire to push it back on when the flux boils and moves it.

Finally in my experience the think you need most in silver brazing is heat. Not high temperatures but a lot of heat. Weed burner heat on big assemblies (like 4" and bigger). The faster you get things to the soldering point the better the flux will work - cook it long enough and the flux will burn out. I like to get the silver solder melting into the joint in a couple of minutes max. If you can try surrounding the part with firebrick on most all sides to contain the heat.

 

[kvom]

Everyone I know around here prefers the black brazing flux over the white. Brake cleaner is also good for degreasing.

 

[GWRdriver]

Aydelott,
I'm surprised your instructor didn't go instantly to the next logical step (or remedy) . . just clean the oil off! I don't know what kind or size engine you are building but if it's a model (as opposed to a full size engine) Loctite will do perfectly well for both steam and IC. It will be important for success for the journal/shaft fit clearances to be held close to Loctite specs, the joints need to be kept very clean, and then I typically pin the journals (see the photo.) This has resulted in 100% success for small crankshafts. I'm not saying don't silver solder it, this is just the way I do it and I'm happy with the results. The only thing I would change about the crankshaft in the photo (a Stuart D-10) is for purely aesthetic reasons I would use steel pins next time rather than brass. (Horrible photo color, something went wonky with the photo editor enhancements.)

Here's another thought to consider . . . in model practice, where only a few thou' of excessive clearance can make the difference between a close and a true-running fit and a loose wobbly fit (in a shaft and wheel for instance), Loctite presents us with a small conundrum. Shall we adhere to their clearance recommendations (maybe 3 to 4 thou' on a small shaft) and create a fit that could easily set up misaligned, or reduce the curing clearance and reduce the potential for wobble but also reduce the effectiveness of the Loctite?

What I do in situations like that is to first turn my shaft (or wheel seat) to a tight sliding fit, almost a light press fit, in the wheel (or crank, etc) and then I come back and turn a shallow groove or channel almost the full width of the shaft seat to the optimal clearance recommended depth for the Loctite. This creates a narrow shoulder on the inboard end of the seat and a kind of locater ring on the outboard end. The channel is filled with Loctite and the wheel pressed on and the shoulder and ring serve to exactly center and align the wheel or crank on the shaft while the Loctite cures. I have had 100% success with this technique (ie runouts at or below .001") so far as alignment goes, but I still pin cranks.

 

[rkepler]

Like Harry I tend to glue and pin cranks when circumstances permit - here's a shot of the layup of the crankshaft for my 3 cylinder Shay on the surface plate:

The shaft went straight through and was supported by the bearings in the crankcase, this gave me the positions for the journals and the captive eccentrics (not in this picture). It also let me set the proper angles for the throws. I centered things by using an automatic center punch to peen small dings all around the shaft - using the automatic punch tends to keep the sizes of the peens the same so that the shaft centers with a light press but retains enough gap around for the Loctite. After gluing up I put taper pins through every joint (and even put loctite in them "just in case" after some internal depate on glue joint thickness and such) and remove the spare shaft in the journal. It seems to have worked as the Shay has run 120+ miles and is just broken in (I may need to tighten up the eccentrics and reset the valve timing this winter).

And I forgot to mention using brake cleaner as a degreaser - shame on me. I'm still hoarding my remaining stock of 1,1,1 trichlor degreaser and tend to not think of it except for extreme cleaning needs (as in gluing up crankshafts). I should buy a case of the replacement so I could return to spraying brake cleaner with abandon.

 

[Aydelott]

thanks for all the info he did try to clean the oil off and even burn it off he said nothing worked but i have just got some jb weld i think im going to try that next its cheaper then silver solder an flux anyone ever tryied that???

 

[MachineTom]

Each material you deal with in life has a useful purpose range. Having used JB weld with success in engine crankcase holes, sealing cracks in transmission housing, JB did the job. I believe that it is beyond its range to try in holding together a crankshaft. You have not said in what manner it will be applied, it has no capilary action, so just smear it on the journal and press it together?

With 650 hours invested in your work, I won't want to make a cheap mistake in this regards.

 

[skyline1]

If your "Instructor" tried to burn it off that may be your problem he probably did just the opposite and baked it on, I use just such a process for oil "blacking" components. It actually bonds to the surface and the only way to get it off is to physically abrade it off with crocus paper or fine wire wool.

I do it with boiler casings and it won't come off no matter how hot it gets. like this



The silver solder I use is Johnson Mathey Easy Flo and Easy Flo flux but it's cadmium bearing and so is getting hard to obtain. I doubt the odd bit of silver soldering will fill your body with cadmium it's health and safety gone mad if you ask me.

They are a pretty world wide company so you should be able to get it in the States the flux is an active fluoride flux which you mix to a thick paste and apply to the joint after cleaning it well.denatured Alcohol or industrial Methanol is ideal as well as a good mechanical scrubbing with wire wool or emery paper.

Regards Mark

 

[Aydelott]

if you look close it his picture the crank is three parts the center an two journals in the middle being one part an the out sides with the lobe being the other they fit into a .200 pocket the same od with a .300 hole all the way threw so the lip on that pocket would be takeing most of the pressure its not going to be just jb weld holding it, an the jb says it is good to 2425 psi what do you think i cant get a better picture to really see it till tuesday the rod the crank arm spins on is part of the outside so its only needs to be fixed on the side with the hole

 

[goldstar31]

OK, this is my first posting here but it time to debunk a lot of old wives' tales.
The first thing is to get it clean. Forget the so called expert who suggests some liquid cleaner as this only dilutes the contamination.
You have to get it rubbed clean with something like steel wool and then prepare your powder flux mixed to a paste with a drop of household washing up liquid.
If you are any great shakes and you are doing something like a model locomotive boiler, you might have to pickle it clean with dilute sulphuric acid. |No, don't think about stuff from a car battery. I've known people who used things like vinegar bodied sauces. British HP sauce is great!
Back to ordinary silver soldering and if you want, use a scraper end to remove whatever muck there is. Again, you can use silver solder paint which is fine silver dust with an acid to etch the work. So you are back to sulphuric or hydrochloric or acetic acids. Frankly,, I like solder pastes and once they are hot enough- that is little globules of molten silver, you wipe it clean with a dry paper towel or tissue. This leaves a 'tinned' surface ready for proper soldering.
Again, your rod should be clean and warmed a little enough to dip in dry flux. so that the flux sticks ready for the joint.
If you read this carefully, you will find that all that I have written is concerned with cleanliness at all stages.

I hope that the foregoing is useful.

 

[digiex-chris]

another problem with burning off the oil is the heat. Heat without a barrier to oxygen like flux increases the rate of oxidization. If any color change took place from the heat, you've got a layer of oxidization. Solder of any kind won't stick to oxidization. I definitely think it's inaccurate saying that once oil comes in contact with your part you won't be able to silver solder it, since many of us use a cutting oil to manufacture these parts.

Clean well, brake cleaner is fantastic for that. Rub off any oxidization that may have formed while you messed with it (any discolouration of any kind) with steel wool or something. Don't touch it with even your fingers or you've gotta degrease again!

Practice on something that's not your final part.

 

[skyline1]

Goldstar31

I agree with you 100% cleanliness is indeed next to godliness with silver soldering and mechanical abrasion and elbow grease is the best way to achieve it along with a good active flux and an acid pickle for copper. You do silver soldering just the same way I do.

Regards Mark

 

[rkepler]

OK, this is my first posting here but it time to debunk a lot of old wives' tales.
The first thing is to get it clean. Forget the so called expert who suggests some liquid cleaner as this only dilutes the contamination.
You have to get it rubbed clean with something like steel wool and then prepare your powder flux mixed to a paste with a drop of household washing up liquid.

Steel wool will introduce oil to whatever you rub it on, and "washing up liquid" (dish washing liquid in the states) is mostly surfactants that will have an unknown effect on the flux action. If the point is to have clean metal at the joint I'd suggest that both of these activities would be counterproductive.

If you are any great shakes and you are doing something like a model locomotive boiler, you might have to pickle it clean with dilute sulphuric acid. |No, don't think about stuff from a car battery. I've known people who used things like vinegar bodied sauces. British HP sauce is great!

HP sauce is OK on fries, but I'm not sure that I'd use it on a boiler - the copper would make it taste funny.

But "Sparex" is an acceptable substitute to all of those, and if you're cheap like me you can just go to a pool/spa supply and pick up some sodium/potassium bisulphate and use it at the rate of 1 lb/gallon (handy since a 5 lb supply works in a 5 gallon pail). I tend to cool work in the pickle, that tends to blow scale off the copper. It also plates some copper back onto steel (requiring some cleaning) and can splash some acid around - I've lost several pairs of jeans that way.

Back to ordinary silver soldering and if you want, use a scraper end to remove whatever muck there is. Again, you can use silver solder paint which is fine silver dust with an acid to etch the work.

Most of the silver braze acid fluxes I've seen are boric acid based, I've never used it in modeling, it's much more common here for use on silver (lots of jewelry making around here). All the silver brazing fluxes that I know of for copper contain borax and usually some fluorides to remove oxides and keep them off during the brazing process.

But your point is taken - you need clean surfaces to braze, and you need flux that stays in place when the joint is being heated. I'll add that you need enough heat to get the joint hot enough for the braze to melt and fill the joint before the flux burns off. When you have all of those things in place the braze flows into place like magic, a neat process to watch.

 

[davedfsme]

Brake cleaner comes in a spray can. Not only does it dilute oil and dirt, but it physically blows it off your parts. That doesn't mean that it is CLEAN after using copious amounts (it leaves a white residue) but all oil is GONE if you are thorough. Follow with compressed air to get rid of the contaminated solvent faster than it can evaporate, which would re-deposit residual contaminants. Use it as a first step to cleaning, it makes the physical part of mechanical cleaning a lot easier if you are not smearing "grease" around on your parts. Wash your steel wool, "Scotchbrite" or other abrasive with brake cleaner (or alcohol) to remove any residual oils or other contaminants from the abrasive, and rub off the oxides and dry contaminants on the surfaces before fluxing. (Most commercial steel wool is treated with a very light "drying" oil to resist oxidation during storage) Pay more attention to "IDs" of finished parts than "ODs", simply because they are harder to clean. Flux all mating surfaces completely (as mentioned before) before assembly. Use a commercial flux to suit the brazing alloy and materials you are using.

"Yo' Mama" might have told you that "Cleanliness is next to Godliness". Underarms might smell a little in the shop without affecting anything, but if you want success with any type of brazing for critical applications . . . surgical cleanliness is your goal. The job of the flux is to protect the surfaces from oxidation during heating AND to remove what you might have missed, in that order. Asking it to chemically clean the parts that "you didn't bother to" is a recipe for failure.

The same goes for adhesive methods, except now you don't have flux to help bubble out any missed crap. Glue bonds are only as good as the surface they are trying to stick to. If it ain't clean, it won't stick!

IMHO, JB Weld is best for replacing missing (or worn away) material. Asking it to reliably provide a shear strength in a "thin film application" is asking for trouble, especially if your surfaces are covered in crud. For critical clearance applications like a crankshaft, you would have better luck with Loctite, if your parts are clean. Recommended clearance issues can be dealt with by progressive fits as suggested above, and/or by "zero-stress" assemblies, relying on position during cure to allow the parts to locate themselves by fluid dynamics (surface tension???) to insure concentricity and alignment of pins and bores. Low viscosity, high strength adhesives, correctly applied, will logically give better results than the other way around.

DJD

 

[goldstar31]

Actually a professional would read some of the replies with some misgiving. I tried to simplify my reply so that the beginner would have success.
Whether this was done, I have yet to be informed. Instead, I got a number of contradictions and tangents away from the original issue.

Actually, the point was missed about oil and cleaning with brake cleaner and alcohol. I spent four years after retirement doing a City and Guilds in Motor Vehicle Restoration and despite the fact that this was somewhere where brakecleaner should have been a common thing, we never had any! So much for such advice.
Again, oil is virtually impossible to remove from cast iron. Cast iron is actually porous. Back to the drawing board!

In the 1950's, after the Goldstar bit in my life, I was involved in 'tinplate or ternplate' and it was delivered by the thousands of tons( tonnes) and it was oiled.
That stuff became the raw material for both the soldered can bodies and the ends. It went through the solder horses and was sealed with lead solder.

So back to this Happy Retirement away from demands of a real job and we had to learn 'leading' which is filling and filing panels with lead prior to painting.
What was the lubricant? Well, the book says either vegetable oil or traditional tallow. In fact tallow is the 'flux' for lead piping.

So where have most of you gone wrong? You have to do a bit of chemistry and learn or re-learn about heat and fatty acids. If you take oils up to a high heat and the oil changes from a lubricant etc to an oil which is a drying oil and which will oxidise into a varnish or medium for oil based paints.

If taken further, it will change yet again- and taken further up the heat range it will probably fall off!

I DID try to simplify even this reply. Unfortunately, one walks away from the opportunity to pass on further free advice.

Good Morning!

 

[pete]

DJD,
SPRAY TYPE BRAKE CLEANERS? Are you completely serious? Ever hear of that Phosgene gas used in the trenches during the first world war that was meant to actually KILL? Add heat to the right spray on brake cleaner and that's what you get. EVERYBODY should know that by now since it's been well documented and common knowledge for years. I know more than a few welders that would do their very best to get anyone fired that used it prior to them welding on anything. I'm about as far from a safety freak as you can get, but I can't believe you would advise using brake cleaner prior to heating anything.

Pete

 

[davedfsme]

Goldstar,

I was not trying to imply that you were wrong in any way. I was merely suggesting that a person could make the job easier on themselves by getting rid of as much oil and crud as they can BEFORE mechanically cleaning their parts. It is still necessary to abrade the surfaces, pickle is an excellent plan, active flux for the materials used, heat range and time spent at heat needs to be selected and utilized.

Please keep in mind that lead based SOLDER is entirely different than silver BRAZING. Temperatures used for soldering don't burn the petroluem/acid solder pastes or the "killed" fluxes, if properly applied. The presence of lead solder WILL destroy the wetting ability of the best grade "silver solder", which in itself is an antique misnomer. The only "solder" which should be considered as "silver" is the "high-melt" lead solder which contains ~2% silver. The rest of this discussion has been concerned with "Easy-Flo", "Argo-bond" etc. I am not about to wipe a joint which is at a red heat!

It's that whole bit about the oil oxidizing at heat which has me stymied . . . We are desperately trying to exclude oxygen from the surface to prevent the metals from oxidizing. (Prime purpose of the flux . . . remove residual oxidization, and prevent any further oxidization from occurring.) Brazing fluxes are water or alcohol based, typically containing flouride or boric acid compounds . . .
solder paste is zinc chloride, if I remember correctly?


I think we are referring to different processes, using different materials, at different temperatures.

DJD

 

[davedfsme]

DJD,
SPRAY TYPE BRAKE CLEANERS? Are you completely serious? Ever hear of that Phosgene gas used in the trenches during the first world war that was meant to actually KILL? Add heat to the right spray on brake cleaner and that's what you get. EVERYBODY should know that by now since it's been well documented and common knowledge for years. I know more than a few welders that would do their very best to get anyone fired that used it prior to them welding on anything. I'm about as far from a safety freak as you can get, but I can't believe you would advise using brake cleaner prior to heating anything.

Pete

Pete,

Yup. I am completely serious. Only as a pre-treatment, to remove oil-based crud, followed by scrubbing to remove oxides and brake wash residues.

Who said anything about cast iron?

Anyone who applies heat to volatile compounds is asking for any manner of combustible troubles. As a pre-treat, the majority of the materials used for cleaning the parts will have evaporated long before any serious heat is applied. We weren't talking about welding "wet" components here. You still need to scrub the parts back to bare metal before fluxing. You might want to consider that the fluxes used for silver brazing are in themselves often flouride compounds, and the alloys used have historically contained cadmium as a wetting agent. This is not a "healthy" process to start with, and "adequate ventilation" is a prerequisite.

But, you may have a point that I am not aware of. I also smoke cigarettes, ride motorcycles, drink whiskey, eat fast food (occasionally), and am still alive. The biggest problem I have with silver brazing is using just enough alloy to form a meniscus fillet, mine always seem to have a little run of excess somewhere or another.

Regards,

DJD