I have 4-40 control rods and Dubro threaded ends that I'm trying to solder and I can't get the solder to stick. I'm using flux and silver solder with a small torch. The metal just won't take the older. I heat it up plenty, and use flux on the joint, but the solder just drips off.
There's gobs of it on my basement floor.

I solder electrical very well and I know something is very wrong here. Is 4-40 control rod and the Dubro control rod ends solderable?
Do I have to sand down the control rod first?

Thanks,
Joe

Yes, alway's sand first.... also the clevis's my be stainless steel or a non- ferris metal ...Us a magnet to check this ....I hope this help's ya ........JW

might want to try to scuff up the smooth end of the rod where you are putting the clevis im fixing to go through the same thing with my funtana im going to use 4-40 rods all the way around with threads on one end and smooth on the other. I could be wrong in tellilng you to scuff it up but that is what im going to try and do hope this helps you, mike

Scuff it up and wipe down with alcohol to remove any oil.
sta brite works better for me than flux on control linkages. You can get it in large quantities from electric supply houses instead of the GP small bottle.

Besides scuffing the rod, make sure you clean it from any grease or oil. Also - make sure that you are not getting the joint dirty with the flame of your torch. Small amounts of soot will keep the solder from sticking too.

Joe,

Don't melt the solder with the torch. Sand the joint, get some flux inside it, and heat the joint. Pull the torch back and touch the solder to the joint. Orient it so the solder will flow down into the joint, if possible. If you don't get it hot enough to melt the solder, heat more.

Now, if at that point you get the solder to melt, by touching it to the joint, and it runs off... maybe you'll have to get solder ends, rather than threaded ends. Dubro makes them, no threads, just formed sheet metal.

That's the best I can do, going by your description. Good luck,
Dave Olson

I've never had very good results with a torch. I generally use my UT100 with a soldering tip, but a conventional soldering gun or iron better than 35 watts will work just fine with proper surface prep.

Control rods are coated with an oily substance that prevents rust, but I think it is a side effect of a lubricant used in the drawing process... not an intentional coating for our benefit, but rather a cost-cutting measure of bypassing a cleanign process.
Regardless, you need to go over the area of the rods to be soldered with fine emery paper, or even wet-or-dry (I use whatever I happen to grab).

One problem with a torch is overheating... getting the rods cherry red will soften them.

first off, I hope you are using a solder clevis, not a threaded clevis. The rod just needs to be scrubbed with steel wool and then cleaned with lacquer thinner. I usually clean the clevis with thinner too. Are you using the silver solder from Great Planes, etc that comes with acid flux? If you are doing all this and it still wont take, you might be getting it too hot. I use a mini-torch attachment, a pencil like tool that attaches to a propane tank with a hose, but I have not seen them for sale recently, unfortunately. If you are using a torch that's too big, try a soldering iron.

Peter

I solder 4-40 hardware on the electric stove burner in the kitchen all the time, works great.

Thanks for all the tips. I"m not sure which one of your tips worked because I basically did all of them. I think the flux was the key and not too much heat. The flux came in a little can and really should be inside the solder. I dipped the solder in the flux and touched it to the metal and things started to flow inside the joint (finally). I also took emory cloth and took the finish off the 4-40 rod. Man this is touchy stuff. I thought it would be easy. I gave all the control rods a good pull and they aren't coming apart. You can tell by how the joint looks when you know there's solder deep inside there. It clings to the joint real tight.

It didn't make sense when I saw all the flux just burn off and didn't help the solder flow into the joint. Once I dipped the solder in it, the process worked better. It seems like you need them both applied at the same time.

Thanks again,
Joe

You might want to invest in one of those big old heavy Weller 145/210w solder irons. I used the flame method and then found this old high power iron. Man what a difference! takes seconds to solder joints. In fact I did 4 last night. Its not good for electrical as its 2 high wattage.
just a suggestion.

Hi!
Well it's really simple if you have adequate equipment.

First of all it is vital when soft soldering that you clean the surface that you are about to solder.
That means using sandpaper and sanding away all dirt and grime.
Using acetone prior to sanding is a good advise to get rid of the grease and grime.
Soft soldering is mostly done with an electrical soldering iron........I use a WELLER 50W soldering pen with iron-plated exchangable tips (professional type) which is 30 years old that hold a constant temperature.
Soldering irons (angled and straight) could be found at general-stores but these have often un-plated copper-tips and these are not to good to use..more than a few times because the tips oxidizes and get black from sot (you see... iron-plated tips don't oxidize or get "dirty" from flux in the solder).

If you are about to solder together two piano vires.... let's say two 3mm pianowires......making a landing gear...it is much better to wrap them togetter first with thin copperwire so that the surfaces are held tightly together...then adding flux ...and then solder.
The best solder/flux on the market is the Great Planes "Stay Brite solder" It comes complete with soft solder (ad says its 5 times stronger than ordinary soft solder....and I agree...it is superior to any soft solder I 've tried in 30 years) and a small bottle of flux.
This flux is so effective that you really don't have to clean the surface before you solder ...just drop on some flux and heat the area with the iron.......then hold the solder against the surface ...still heating it with the iron......and voila! Ready!
The brightest solder finish I've seen....and strongest (soft solder that is).

Regards!
Jan Karlsson
Sweden
http://hem.passagen.se/airracing

Can I get Silver Solder with the Flux inside like electric solder?

I have good luck using plumbing solder. Only put the flux where you want the solder to go, so the job dosen't look like crap. You only need the solder in the joint. Clean the pieces you are about to solder with a piece of sandpaper, and do not touch the joint after you clean it. The oils from your fingers will give a weak joint. clean the flux off with alchohol after the piece cools to prevent rust.

I don't mess around with silver solder for almost anything. It's too expensive and needs too much heat. I use solder clevises all the time and haven't ever had one fail. I just use electrical solder and paste flux. I use silver solder for cabanes and landing gear (sometimes, but not always).

Clean the threaded rod with fine steel wool (not too coarse or it will promote rust).
Dip the end of the clevis in paste flux
Slide the clevis over the rod
Lay the clevis so that the shoulder is resting on a tinned iron
Add solder. When the solder flows, remove the rod and let it air cool.

Don't try to accelerate cooling or disturbe the joint while it's "wet" or it will make a weak joint that will probably crack.

I have not seen silver-solder with a flux core. but Radio shack sells ground up silver-solder mixed with flux in a paste. It comes in a SMALL syringe-like tube. About $3 (last I bought some) If I needed more silver-soldering than I do... its not a good way to get it. Snce I use one of these tubes a year... its cost is not a problem.

One thing to be careful of is that there is a difference between silver solder and silver BEARING solder.
True silver solder is not sold in wire form on a roll... it is fairly hard and is sold in square sticks like brazing rod. A 35w iron is not going to touch it.
Silver bearing solder is named for the fact that it BEARS solder (it's not designed for soldering bearings). It can be as little as 2-3% silver blended in with conventional solder.

Dunno about the stuff that Radio Shack is selling... I have lost a lot of faith in them over the years... their shrink tubing is flat out junk.