Soldering Problems

i4Marc

i4Marc

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Oct 19, 2011
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I read a bunch of threads about soldering. I printed out a couple of Stacy's posts about soldering and read it a few times. The solder I was using was a "pro soldering kit" I ordered from Jantz. This is a roll of Stay-Brite with the matching bottle of paste flux. I cleaned the brass guard and the knife blade (1084) very well. I washed my hands and used nitrile gloves so I wouldn't contaminate the pieces. The guard fit was tight and needed to be press fit. Although, when lubed with the flux, it went on easier that I expected. I placed the end of the tang in the vise with the blade tip up. I applied flux to the guard and the blade at the joint area and fit the pieces together then began to add heat from the tang just behind the guard. I used a heat gun with a reduced nozzle adapter for a more concentrated blast of heat. I took a LONG TIME to try to get the joint up to temperature while keeping the heat moving constantly so the joint heated evenly from all sides. I kept touching the solder to the joint to see when it was ready to flow but it never did. After a long while I thought maybe the heat was insufficient so I stepped it up a bit with a propane torch. Still using a soft blue flame. The solder still wouldn't flow. The flux was still liquid at that point and not over-cooked. Then the solder started to get soft but instead of flowing it just kept breaking off in very consistent 3/8" or so segments. That was strange. Eventually I got frustrated and took it all apart, cleaned it to fresh bare metal and epoxied it. I know.....quitter. But, I still want to learn how to do this. Does anybody have any ideas why the solder wouldn't flow or why it kept braking off in little pieces?
 
Sounds like not enough heat. I solder all all my guards with a heat gun it is very slow to heat up. It would be better if we could talk in person about it. lots of details and different fluxes and solder good luck Gary martindale.
 
Did the solder that broke off ball up? If it balled up and became a liquid drop that didn't flow, you may have overcooked the flux. If it fell off in a piece then rolled away without being liquid, you weren't hot enough, and your torch/heat gun melted the solder instead of the base metal doing the melting.

Practice on some scrap, it's tough to learn on your project peice that you're afraid to hurt.
 
What color did your tang turn? It sound to me like you did not get it up to temperature. It needs to be @ 450 F and it should only take a few seconds to solder after getting to temperature.
 
Sounds like something was drawing off the heat. This is a common soldering mistake. Perhaps it was too close to the vise jaws.
 
I would have taken more time with it but I was sort of in a hurry. The knife is for my nephew. His birthday was this past Friday but the party is today. I'll have to make the sheath for it later.

The solder that broke off did not ball up. As I applied a little pressure against the joint with the solder it kept breaking off in little straight segments. The tang didn't turn any colors. I guess that was the problem. Not enough heat. I suppose in the back of my mind I had Stacy's caution about getting it too hot.

Stickbow54, how long does it take you to get up to temp with the heat gun? Does your tang start turning colors?

Bill, I had the tang set in the vise all the way at the end of the tang. I had a piece of blue shop towel soaked with water clipped around the blade in front of the guard where the plunge line is but that eventually dried out anyway.


Here is a quick shot of what it looks like:

 
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I'm no expert, and I'm sure more experienced makers will be along to help you out. But I'll throw my opinion in, if you like. I generally use a propane torch. You don't necessarily have to have the flame turned way down, just put the flame where it needs to be. On a small knife and guard like that, I would focus the flame on the tang from underneath, as the brass guard will heat up more quickly than the steel.

I don't worry so much about the heat from the torch, as long as I am getting the area I want to hot enough quickly. Meaning, if you turn the flame down, it may put out less heat, but it's going to take much longer, and all that heat is going to rise into the blade. You want the heat on the joint, and bring it up to heat relatively quickly, and you'll be done before the heat transfers much.

If the solder was breaking off, that means it was getting hot enough to start melting, but not flow. Usually this happens when you have the torch still on the work, and the solder gets heat from the torch. I rarely put the solder to the work with the torch still pointed at the knife. Once the joint is hot enough, soft solder will easily flow for sometimes over a minute, which is more than enough time.
 
Very nice knife, by the way. I'm pretty sure your nephew is going to be thrilled.
 
Thanks Sam. We'll see. I'm heading over there right now. I'll keep in mind your suggestions for next time.
 
I use either an air/acetylene or a propane torch. There is much to be said for quickly heating the joint to minimize heat propagation.
For carbon steel ,and brass or other ferrous metals, lead solder works very well. It's melting temperature is well below the tempering range for carbon steels.
The silver-bearing solders like Stay Clean require a higher temperature than lead, but it still is slightly below the tempering range-if you don't keep applying heat. Stay Clean liquid flux is good for either lead or silver-bearing solders.
The silver-bearing solders are necessary for soldering stainless steel.
I keep a spray bottle handy to cool the blade immediately after soldering.
 
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Hmmmmm, so you don't need a silver-bearing solder for ferrous blades with brass guards?
 
I figured out a way that works about perfectly every time, and it seems very easy to me.

I use Brownell's High Force 44 solder, and the #4 Comet flux that goes with it. I think it melts at 475*. I clean and flux the joint, but I am very careful not to get Any flux in front of the hilt. That is important.

When I fit a hilt, it has to be tight on the blade side. It's not that tough. You can tighten it up on the anvil if needed.

I taper the hole or mortice in the hilt so there is a slight gap on the tang side (about .005"). I think it makes it easier to get a perfect fit in front, and it seems to make it easy for the solder to run into the small gap.

Then I take heat sink mud and smear it tight against the front of the hilt and blade. The idea is to keep solder from running down the blade.

I cut the top half off a dixie cup and fill the bottom half with the heat sink mud, then I stick the blade (with the guard already sealed with mud) through the dixie cup, and wiggle it into the cup full of mud. I put the masked blade (pointing down) into the vice. I take a little more flux and let it fill the gap.

I think an acetylene torch works much better than anything else. Even Mapp gas is way too slow for me. I heat the guard more than the tang. It probably takes 20-40 seconds to get the parts hot, depending on how big they are. You know you are close when the flux starts boiling.

That's when I put the heat directly on the joint. in 5-10 seconds the solder will flow right into the joint, but it won't go through.

As soon as the joint is full, I brush off the excess with a little steel bristle brush, and start lightly spritzing with water. I never need to worry about anything getting too warm. Heat sink works.

I don't remember a time this hasn't worked like a charm. I only use sterling silver or brass. I don't like stainless.

I haven't heard of anyone else doing this, so I don't expect much agreement.
 
gg, Is this heat sink mud something you got from Brownell's? So let me understand, you solder with the tip down and heat the joint from the tang side at the joint? So, if the solder supposedly runs toward the heat the tip down orientation of the blade doesn't matter because you are actually putting the heat at the joint?


Thanks Droptine5. This is only my 5th knife I've finished and the 2nd with a hidden tang and guard. I still need to clean it up, fill the voids in the burl, sharpen it and make a sheath.
 
There is no need to make it that complicated. Lots of things will keep solder from flowing-pencil lead, grease, clay, anything will work.
You don't want to use so much solder that it has to be dammed up. Use just enough to seal the joint.
 
I use the Stay Brite kit that Jantz Knife sells also. I saw a short video of its use by a knife maker in the net somewhere and I tried the technique and it worked for me. I solder nickel silver or 416 stainless guards to stainless blades. Here is how it was done: Clamp the blade an guard with tip up in the vise with about half of the tang clamped by the vise. Then spread the flux around the joint as described in the instructions. Then, cut little pieces of the solder into no longer than 1/4 inch pieces...in fact maybe a little shorter and lay them along the joint with a piece and then a space equal to the length of the piece and then another piece and so on. Then with a propane torch play the flame under guard on the tang about 3/4 of an inch below until the solder flows and immediately take the torch away. Use a toothpick or a sharpened 1/8 rod to push the solder into any spaces and reheat quickly. Let it set for a good while and clean up the joint with a Cratex wheel in your Dremel tool. You can clean excess solder from the guard with a piece of 1/4 brass rod sanded to a sharp angle like a chisel or a graver. The brass should not scratch the guard. That is what was successful for me but I honestly have not soldered joints with brass guards. maybe some others with lots of experience will suggest an alternate method. Larry
 
Sorry for the high jack but I've tried what larryz10 describes and the torch tends to blow the bits of solder out of place.
Any idea what i am doing wrong?
 
i4Marc said:
I would have taken more time with it but I was sort of in a hurry. The knife is for my nephew. His birthday was this past Friday but the party is today. I'll have to make the sheath for it later.

The solder that broke off did not ball up. As I applied a little pressure against the joint with the solder it kept breaking off in little straight segments. The tang didn't turn any colors. I guess that was the problem. Not enough heat. I suppose in the back of my mind I had Stacy's caution about getting it too hot.

Stickbow54, how long does it take you to get up to temp with the heat gun? Does your tang start turning colors?

Bill, I had the tang set in the vise all the way at the end of the tang. I had a piece of blue shop towel soaked with water clipped around the blade in front of the guard where the plunge line is but that eventually dried out anyway.

Here is a quick shot of what it looks like:

Click to expand...

This was your problem. You did all the right things to avoid over heating, but you also added something you don't need if you are doing those things. Without the wet towel, the solder would have been able to melt and flow. The breaking off into chunks showed that it was about 25 or so degrees shy of the melting point, and about 40 degrees shy of the flow point. Heating from the tang side, and the heat sink effect of the wet towel as well as the water vapor created caused the whole blade/guard assembly to be too cool.

Don't be afraid in applying the heat. Get in there and heat up the blade and let the solder flow . While it isn't something you want to rush, it shouldn't take minutes to do if the heat is right. 30 seconds is usually about right to heat the blade and guard up to the 400F or so area needed to make the solder flow.



FWIW,
I put a large spring ( about 3" long and 1.25" wide, low pressure) against the back of the guard, and slip a clamping bar on the tang to make the spring apply sufficient pressure to keep the guard snug against the shoulders. It does not need high pressure...just enough to keep things still while soldering. This allows me to apply heat from the ricasso while the solder is applied from the tang side. The gap in the guard is normally wider from the tang side and solder will flow better from that side. The rule on soldering is to flow from wide to narrow ( gap), and flow toward the heat source. The other reason to apply solder from the tang side is that getting solder all over the tang and back of the guard isn't a big problem or clean-up issue. Getting it all over the blade and guard front by applying the solder from the ricasso side can make for a big mess. If the guard fits right, and the blade is heated the proper amount from the ricasso side, the solder will flow from the tang side and make a nearly perfect bead along the blade/guard joint on the ricasso junction. Any spots that resist the solder flowing along the line can be coaxed with a little extra flux and a sharp brass or copper rod having the point dragged along the joint over that area. Another thing to remember is that you don't need to fill the gap in the guard from the tang side flush to the top. All that is required in a solder joint is that the ricasso side has a smooth and complete solder joint. The actual amount of solder to make that joint is very small. Any gaps along the tang side will be filled with epoxy when the handle is installed.

I start out with the blade held in a vise or clamp, tip down. I heat from the ricasso, making sure to heat the blade as much as the guard, and apply the solder as the tang/guard joint through the spring coils. There is plenty of room to get the solder wire in there. Once it starts to melt, I usually apply a little new flux ( I use liquid flux, but a toothpick works for paste flux) and the solder normally runs right along the joint. I apply heat as needed around the ricasso/guard joint to make the solder run all the way around from the back. Don't keep putting in more solder ( unless it needs it), as it will just go out the front side. I set down the heat source and gently turn the blade over and stick the tang in the vise/clamp. I re-apply some heat from the ricasso side just enough to make the joint silvery looking ( re-melt the solder), and then run a pointed 1/8" brass rod along the entire joint. The solder will follow the point and make a perfect line of solder. If there is a spot that resists, add a little more flux and scrape the point over that area firmly. Apply additional solder ( from the tang side) or heat only if needed. Once all is a clean line, leave the blade in the vise/clamp without touching or moving it for five minutes.

Wash off well with dish soap, hot water, and a good scrubbing with a toothbrush. Scrub for a full minute or two. Rinse with TSP or other neutralizer, and wash again with hot water. Time spent cleaning the joint is how to avoid later rust spots along the blade guard joint. Once well washed, set in a warm place to completely dry for several hours, and oil the blade as you would any blade you are working on.

There may be some extra solder on the blade/guard, or the solder line may be a bit larger of an ogee than you desire ( it should barely show if perfect). This is taken care of by a brass chisel. Take a 6-8" long piece of 1/4" brass square stock and file a flat chisel edge at 45° on the end. This will allow you to cut/scrape away the excess solder without damaging the blade or guard. Re-sharpen as needed. Take another piece of 1/4" square brass stock and file its end at 45 degrees to make a "V" shaped chisel. Use this to clean up the fine details along the joint if needed. Sanding off excess solder should be only a last resort, and indicates you used way too much solder and heat. Use 400 grit paper to remove solder. Turn the paper to fresh grit every couple strokes, as you want the paper to carry away the solder swarf, not rub it into the blade. Wet sanding is good here.

You are now ready to continue your knife project.
 
Thanks Stacy. In another thread some time ago you mentioned that "the surfaces must mate well. Solder isn't a filler compound, it is a jointing material. It flows by capillary action . The closer the joint, the better the flow. This is up to a point though. If the joint is clamped too tight, no solder can flow in at all. This will result in a solder starved joint....which will fail." Here is my question. If a guard is press fit into place will that cause a solder-starved joint?

Also, what combinations of metals can be joined with the low temp silver bearing solders?

Ferrous blade steels/Brass guards
Ferrous blade steels/Copper guards
Ferrous blade steels/Stainless guards
Ferrous blade steels/Nickel Silver guards
Ferrous blade steels/Mild steel guards
Ferrous blade steels/Wrought iron guards
Stainless blade steels/Brass guards
Stainless blade steels/Copper guards
Stainless blade steels/Stainless guards
Stainless blade steels/Nickel Silver guards
Stainless blade steels/Mild steel guards
Stainless blade steels/Wrought iron guards
 
i4Marc said:
gg, Is this heat sink mud something you got from Brownell's? So let me understand, you solder with the tip down and heat the joint from the tang side at the joint? So, if the solder supposedly runs toward the heat the tip down orientation of the blade doesn't matter because you are actually putting the heat at the joint?
Click to expand...

Thanks, you understand really well!

Heat sink can be found wherever there is welding equipment.

First, I found soldering guards to be kind of a pita. I didn't practice it a whole lot, because there is no room for error when you are soldering a guard onto an etched blade. The blade is basically finished. I don't have the option of "cleaning the joint up". It has to be perfect. That's why I tried to figure out a better way for me.

I solder with the tip down, and focus on heating the guard. You have to keep moving. I only heat right on the joint a little when the flux starts boiling, because that's the sign that tells you you are close to the right temperature.

You understand me correctly. I believe using gravity is more influential and consistent than trying to draw solder against gravity with heat.

I seal off the front of the guard to keep flux from running down the blade. I use a Bridgeport to mill the hole, so I can make a tight fit easily. I don't think I've ever made one tight enough to keep hot flux from leaking through, which means solder will leak through too.

Bill, graphite or soapstone will keep solder from sticking, but they won't keep flux from flowing, which means solder can follow it.

I can not stand solder leaking out.

Call it "damming it up" if you want. Heat sink mud does seal off the joint. Flux and solder won't run through. I don't need more solder than anyone else because I can make my joints as tight as I want.

Heat sink also cuts the heat off at the front of the guard which is exactly what it is made for, and helps prevent overheating the entire assembly.

The ricasso barely gets warm, which is of great importance to me. I don't want my ricasso to get to 475*. That was one of my main concerns in devising a different method.

The joint is filled in a couple seconds, and it stays full. It only takes a few seconds for the solder to solidify, as you can spritz with water the second the joint is full. None will leak out.

It may sound like I'm wasting time with all this foolishness. I'm not. It takes about a minute to get the mud in place, and it beats the hell out of cleaning solder from the blade.

Of course I think everyone who already has a working method will dismiss this, and that's fine. If you are easily getting perfect joints, don't try this.

I have very much respect for Stacy. I am positive his joints come out perfect, but the description of how he arrives at that sounds pretty complicated, and he still ends up cleaning solder off the blade.

If it weren't for the fact that I can't afford to get any solder on the blade, I'd follow Stacy's instructions. In fact, I'm saving them so I can practice it. It sounds really cool.
 
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