Help on soldering a threaded coupler
 

Hello all,
I'd appreciate some advise on soldering a threaded coupler. At my first attempt I sanded the 2/56 rod and cleaned it with acetone, I then applied flux to the rod inserted it in the coupler and heated it as one unit. The flux burned off rapidly and then the solder melted. After I let it cool I tested it for strenght and it pulled out. The control rod looked sort of black. Is there something I did wrong? Also the final product is not a nice looking product (solder all around the joint) versus when you see a nice plumbers soldered joint. Any help would be appreciated.
Thanks,
Pat

Could be just the wrong solder or the wrong flux. Is this piano wire? Might need a acid flux not a rosin flux.

I have had good luck with silver solder for plumbing. It is not as hard to use as the full on silver solder you may as well be brazing with.

http://www.homedepot.com/p/Oatey-0-2...3#.Uhqq_D-0TUk

http://www.homedepot.com/webapp/wcs/...93&R=100157093

Buzz.

Get some Silver Solder with some Acid Flux and it will work better for you.

Frank

"The flux burned off rapidly and then the solder melted. "

If you are using a flame, it sounds like too much heat. The flux should not burn off, just turn to liquid. Now it sounds like the surface is oxidized, and you will have to start over.

Les

p.s. Been at this a loooooong time, and NEVER found the necessity for acid flux.

Yep agree you got it too hot.

For the type of work you are doing, this is a great product. http://www3.towerhobbies.com/cgi-bin...&I=LXFS75&P=ML

Thank you for all the replies,
I'm using a 230 watt soldering gun, so it sounds like that's too hot. I have a butane soldering iron I'll try that. Is there a way to clean and flux the inside of the coupler? I also think I used plumbing flux I had laying around. What type of flux should I get. Also the solder was bought at home depot and it said it was used for metal gutters, sheet metal, and automobile use. I'll first start with the lower heat.
Thank you,
Pat

I like to tin each part separately first if it looks like it may be trouble.

Your gun looks ok. I suspect they sold you acid flux. I use standard radio type 60/40 rosin core solder, and paste flux.

Les

"I like to tin each part separately first if it looks like it may be trouble"
That does not work when you are dealing with threaded parts.
Some of the clevises are plated, and that can cause a real problem.
I've had decent luck with CA if the rod, clevis, and nut is cleaned before the CA is applied.

Standard plumbing solder and flux will do the job just fine. Rosin flux will too, as will pretty much any kind of standard solder (meaning not brazing rod aka "silver solder"). As others have mentioned, you overheated your piece. It will be easier to get it too hot with a torch, but you can still get good joints if you'll just be careful to watch the flux. When it bubbles, you're at the right temp. Manage your heat to make the solder flow well but not any hotter. What really makes for a strong joint is for the heat to be just enough to make it flow like water so that when you take the heat away the solder hardens immediately.

I use a good grade of silver solder and have never had (knock wood) a solder joint failure with threaded connectors or other soldered "welds". Clean with acetone and flux properly.

http://www.rcuniverse.com/forum/atta...mentid=1913742

http://www.rcuniverse.com/forum/atta...mentid=1913743

http://www.rcuniverse.com/forum/atta...mentid=1913744

I take a drill bit and run it back and forth to scratch it up inside there,,, then dunk it in the flux.

I use either an iron or a torch,, either will work, if you heat until things start turning black, you've gone to far

good luck

Just a thought. I had the same problem trying to solder onto a needle valve that I made up. I wanted to solder a nut on the end for adjusting it, and the solder would not stick to the threaded rod, but stuck to the nut no problem. Turns out that the threaded rod is stainless steel, and is much more difficult to solder. Maybe there is a different solder or flux for the stainless. I will keep my eye on this to see what will work on stainless because I still want to get this done.

You need a flux made for stainless aspeed. The issue is that the chromium actually forms an oxide on the surface of the steel. It's chemically similar to rust actually, much the same as regular carbon steel will get that black patina on it after a while. But the chromium version is really tough and it forms instantly when there is oxygen present, so you can't clean it off in order to get down to the bare steel. If you scrape it off another layer will just form right under it. So you have to have a flux that can dissolve that oxide and then do what all fluxes do which is block oxygen from getting to the metal.

I'll indulge a pet peeve of mine for a minute: Soft solder is not silver solder. Silver solder is for brazing, which is a much higher heat process and an altogether different skill set that doesn't have any applications in RC. What most guys on RCU call silver solder is actually soft solder that has some silver in it. If we could call it silver bearing solder instead of silver solder there would be much less confusion.

Silver bearing solder works great for soldering stainless steel as well as standard music wire, copper, brass etc. The only caveat is making certain of thorough cleaning of the acid flux. If some flux is left behind it will eventually corrode the steel and ruin your day. Nevertheless, it is a simple job to solder with silver bearing solder since it wicks easily down to the steel we want to solder. Tinning the parts first works best if you have the room when fitting the parts together

Real silver brazing is totally different type of soldering-brazing that heats the parts to softening temperatures. One would have to re-temper the steel to make it useful again

Back to regular low temp soldering with either paste flux or rosin core solder, the biggest errors are made when the parts are not hot enough to melt the solder. Using an iron with enough wattage is the key. Small joints are easy but larger joints such as landing gear strut build or cabane striuts require as much wattage as practical. A simple technique I use generally for large jobs is to first get one small area hot enough to melt solder and actually apply a dab of solder there. Heat transfer from the iron or gun to the joint jumps dramatically when making wet contact. Feeding fresh solder to the hot joint becomes elementary and adding a dab of paste flux is practically always beneficial, even with rosin core solder

Hello all,
First regarding Stainless steel material, the threaded couplers I used were a silver color (I'm wondering if that's stainless steel) the others that I'm going to try that I have are a brass color (I'm assuming it's brass). I'm going to order a combo kit from a hobby shop and start from scratch. This is what I'm going to order tell me if you think it's the correct product.
http://www.hobbyfever.com/product_in...ducts_id=13241 And I'm going to try it with my smaller soldering iron.
Thanks for all your help,
Pat

" the threaded couplers I used were a silver color (I'm wondering if that's stainless steel)"

Not necessarily. Nickel plating is common and silver in color.

I'm not sure why you are using silver /silver bearing solder at all..Plain old radi 60/40 works just fine and does not special fluxes.

Les

Hi Les,
Thanks for your input. The reason I going with Silver Bearing solder is that I read here at RCU that for any mechanical strenght to use Silver bearing solder. That;s basically the reason. If this doesn't work I just may go back to electrical soldering.
Thanks again,
Pat

That's what you get for getting your information off the internet!

Smarty pants comments aside, yes, silver bearing solder is harder. So if you make your joints the wrong way it will be less likely to fail. The right way is to have a tight parts fit and make a joint that is mechanically strong to begin with, and then use the solder as glue that holds it together. In your application, there is plenty of metal to metal contact in the socket of the clevis that the soft solder isn't going to fatigue and come loose. If you doubt me on that, just take a piece of soft solder and pull on it, twist it, bend it, try to break it, to see how strong it is at room temperature. A classic wrong way to do soldering is to lay up a landing gear and just put the wires against each other and solder them. That would depend on the solder for strength, and would likely fail within the first year. The right way is to lay it all up and tightly wrap the joints with copper wire so that the solder only has to act as a glue to keep the wire in place.

Basic plumbing solder and acid flux will give you a joint that is stronger than the surrounding metal provided you make a proper joint and do proper soldering. If you use plumber's flux, you can wash it away with water when you are done to alleviate any worries of it causing corrosion later on. I've heard guys worry that the acid will stay in the joint under the solder and cause corrosion from the inside before, which is not possible unless you do bad soldering to begin with and don't actually bond the pieces.

"Basic plumbing solder and acid flux"

I'll argue against that until the cows come home, if they ever do. There is no call to use acid flux, and you CANNOT get rid of it by water rinse only. It must be neutralized by baking soda (I think that is what does it). If you do not believe that, take your car battery out, there will be residue of Hydrochloric acid left on the surface by virtue of the results of charging. Wash the battery off, then sprinkle baking soda on it. All the boiling of the soda will be caused by acid STILL on the surface.

In the case of our landing gear, it is not even possible to get "flow" across everything, because there are pockets that you cannot even get water into, let alone flow through.

Les

I'll indulge a pet peeve of mine for a minute: Soft solder is not silver solder. Silver solder is for brazing, which is a much higher heat process and an altogether different skill set that doesn't have any applications in RC. What most guys on RCU call silver solder is actually soft solder that has some silver in it. If we could call it silver bearing solder instead of silver solder there would be much less confusion.

YES it does. Soldering a bung in the exhaust header....
try that with soft solder lol.

LesUyeda- soldering flux is not battery acid. They are different chemicals with different properties. I worked for a couple of years for a plumber, so I do have some basic knowledge here. Plumbing flux is specifically formulated to wash away with water so that it doesn't hang around inside the pipe and cause corrosion or contaminate the water. I've worked on copper pipe that was soldered with acid flux 40-50 years previously that showed no signs of corrosion due to acid being left behind. I also soldered up a landing gear about 4 years ago using my plumbing stuff and as of now it also is showing no signs of corrosion.

a70eliminator- I stand corrected! No way you could solder up anything on a muffler with soft solder. Of course, most exhaust headers are aluminum which is a whole 'nother thing from brazing rod too.

Acid is acid, and does have it's properties. To each his own, and we will live with the results.

Les