Soldering Basics.

[DX-SFX]

For those feeling timid about stepping foot into the world of soldering, it's much easier than you probably suspect. This is a basic introduction to encourage people to have a go.

What is soldering? It's the joining of two pieces of metal or alloy with another lower temperature melting alloy. Some metals solder better than others but in Eagle context, this means usually the easily solderable brass (an alloy of copper and zinc) joined with an alloy generally referred to as 'soft solder'. In nearly all cases, you'll get a much stronger joint than is achievable with an adhesive. This is because solder forms a metallurgical bond rather than a purely mechanical one.

There are a number of solders on the market but only two types need concern us, both of which are quite suitable for our purpose and easy to get hold of. Until recently, the main solder was always going to be regular tin/lead solder as might be used on electrical circuits or by plumbers to solder copper water pipes together. Because of concerns over lead content and poisoning, this type is slowly being phased out although it's still easy to get hold of from model engineering supplies and electronic component retailers. However, there's no need to panic and rush out and buy some before it disappears. The new lead free plumber's solder (which is 99% tin) intended for plumbing and widely available in DIY shops, is an excellent substitute. It behaves the same way and melts at the same temperature so there are no differences in the way you need to handle it.

Tin/lead solder is available in another particular form which some people may prefer but I'll cross that bridge later on.

Equipment:



Forget electric soldering irons. They just don't have the heat capacity to raise the large volumes of brass likely to be encountered to soldering temperature. Note I mentioned heating the brass to soldering temperature. It's not enough to merely melt the solder. If the object you're trying to solder isn't hotter than the melting point of the solder, the solder will only bead on the surface and later fall off into your lap while laughing at you mockingly. For this reason alone, a small butane gas torch like the one illustrated or something similar is a must.

It's also imperative for obvious reasons that you have a flame proof surface to work on. I have some vermiculite boards bought from a specialist company but fire bricks are also good. Common sense should dictate what you choose for a work surface.

Flux:

Imperative if you want good joints. Why? All metals tend to oxidise when heated in a flame. This layer of oxide prevents the solder from bonding with the subject metal. Flux performs two roles. At soldering temperatures, it's acidic and eats through any oxide layer allowing the solder to contact clean fresh metal. In addition it provides a protective layer that prevents further oxidation while the joint is being made. Because it's acidic, it's important to remove it completely after the joint is made. The one I use is again easily available in DIY shops and used for plumbing. It can be used with both tin/lead solder and plumbers all tin solder. I use cellulose lacquer thinner to clean it off but other solvents will work.

Some tin/lead solders designed for circuit board electronics contain a mild flux actually within the solder. The well known UK brand is sold under the name Muilti-Core. This is NOT an adequate flux for fabrication work. Similarly most fluxes designed for circuit boards are inadequate because by their very nature, the flux is designed to stay on the circuit board, and we all know that acid and electronics don't mix. Just get a tub of plumbers flux and use that. Also don't get too hung up on the acid thing. This type of flux is a mix of metal salts suspended in a vaseline base. Technically it's acidic but there's no danger of it eating its way through the outer hull if you drip some on the floor. Just wash your hands after using it.

And finally, try to give the flux an easy ride. It has a number of things to do while it's at soldering temperature so you can help it by making sure the two brass parts being joined are as clean and grease free as possible. Plumbers flux is very good at cutting through even the worst oxidation but cleaning parts can't hurt. Below are some illustration showing the use of flux and its advantages.

[Lee S]

Thanks!! All good info.

L

[DX-SFX]

Photo 'A' shows a clean strip of brass with a short pre cut length of tin lead solder placed on top but no flux. If we heat the brass, the solder melts and flows out over the brass but the flow is limited (photo 'B')




If we brush the area with flux first as in photo 'C'....



.... you'll see that the same length of solder flows over a far geater area and more easily (Photo 'D')



Why is this important? Well, when you come to start joining parts of tubes together, you want the solder to flow into the joint in order to make a strong joint. If you flux the joint first, lay a small precut length of solder in place and then apply the flame, the solder melts and then almost instantly flashes all around the joint by capilliary action. It also means there is the minimum of clean up to perform. If there is insufficient solder to fill the joint completely, just repeat the process. Photos K, L and M illustrate a fluxed joint, immediately after applying the heat and the final joint after clean up respectively:







Note how neat the joint is in 'M'. This has had nothing done to it except to wash the surplus flux off and then rub it with a Scotchbrite pad like you'd use to clean saucepans. If you do find that you've added an excess of solder or the joint subsequently needs a bit of dressing, just clean it with thinners and then make good with an appropriate rat tail file.


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[DX-SFX]

I mentioned earlier an alternate form of solder favoured by some. It's basically a solder paste made by mixing soft solder particles into the flux mix. (Photo J)



There are several brands available and although the one illustrated is a big tub, it can be got in much smaller quantities or in hypodermic syringes. It's designed for model railway enthusiast who construct rolling stock from thin brass sheet and etched brass so model railway stockists are the first place to look. It's main purpose is for what they call sweated joints. This is where it's painted on in advance between two components which are then subsequently heated. It will flow into joints but personally I have two reservations about it. Firstly, it tends to over cook more easily in a flame leaving quite a hard sticky residue behind. The other reservation is that I don't feel it gives such a strong joint in fabrication as the separate solder and flux. However, that's down to personal taste. For example Mark42 prefers it and we're always gently ribbing each other about it so it's another option worth exploring.

Photos F, G, H, I(a), I(b) show respectively solder paste applied to a piece of brass, the same spot after applying heat, the same joint after final clean up, the paste applied as it's intended between two pieces of brass and the same joint after clean up.












Soldering is immensely satisfying and a skill well worth getting to grips with. I can only recommend that anyone has a go because you'll find it's much easier than you first think. The ultimate advantage of it is that if you muck it up, you can simply reheat to take it apart it and have another go.

Slightly more advanced to follow soon.

[rockwellcm]

A great guide there DX-SFX,i have never used no flux solder myself and it explains a lot

I technique i am using on the the 44" cages is to break off a small amount of multi core solder and insert it inside the tube i am about to heat,then heat the tube joint and apply solder to the outside,any bits i have missed are caught with the molten solder on the inside,i have to say your joints are much cleaner,so i might mix and match to see what suits myself

Thanks for the guide

Donald

[DX-SFX]

Use separate flux and you'll instantly see a huge improvement in the speed you work and joint appearance. There's also no reason you can't use flux on the joints you've already made to improve them.

[w8cmp]

Fantastic stuff...

Now I need to go and get a butane torch like that one. I have a small one but I just don't think it's man enough for the job.

I already have the solder, flux and brass - need to start cutting and shaping now and then I can have a go !

[rockwellcm]

Originally Posted by w8cmp

Fantastic stuff...

Now I need to go and get a butane torch like that one. I have a small one but I just don't think it's man enough for the job.

I already have the solder, flux and brass - need to start cutting and shaping now and then I can have a go !

Just a quick saving for you Chris B&Q had the torch (not an RS one) for £9.99

Scewfix had the same torch for £20.00 and a different brand but same torch is £20 in Argos

Hope it saves you a £10

Donald

[DX-SFX]

They are refilled using the pressurised butane cans you can buy cheaply at newsagents to refill cigarette lighters. Worth getting a couple of can's aprox £1.30 each. Each filling of the torch lasts about thirty minutes continuous use and each butane can refills about thirty times.

[w8cmp]

Originally Posted by rockwellcm

Just a quick saving for you Chris B&Q had the torch (not an RS one) for £9.99

Scewfix had the same torch for £20.00 and a different brand but same torch is £20 in Argos

Hope it saves you a £10

Donald

Cheers Donald...need a trip to my local B&Q as well as Halfords nearby. Need stocks of grey primer as well as some more Ford Diamond White as my own resin 44" build is progressing (slowly).

[Mark42]

I only tend to use the paste, on it's own, on close fitting flat parts. As Chris says I don't think it's strong enough for most pipe connections which is why I always add small precut pieces of solid solder to the mixture. On my next Eagle builds, 22 & 44, I will be mostly using the process shown above.

Nice informative posting here Chris.

I have the same torch myself, it's very nice, I think I got it from Machine Mart.

[DX-SFX]

Yes, I use it for the bulk of my work. I must have had that torch for nearly fifteen years or so. There's very few joints on a 44" it struggles with and there's always a simple blow torch for the most demanding. The self igniter is the biggest plus. Certainly one of the most useful and much used bits of kit in my tool box. Trish occasionally pinches it to crisp the top of Creme Brulee.

[Guest01]

Originally Posted by w8cmp

Fantastic stuff...

Now I need to go and get a butane torch like that one. I have a small one but I just don't think it's man enough for the job.

I already have the solder, flux and brass - need to start cutting and shaping now and then I can have a go !

Ive just bought one from ebay at about £8 with free p and p,also i bought a tin of refill for a £1 ,bargain or what?

[Rdrunner]

Thanks for that detailed article DX, your effort is well appreciated

[richardlamer]

Great info there DX, thanks. I've almost finished all the fish mouths for the spine and can't wait to solder.

[McTodd]

This is a fantastic guide, DX-SFX, thank you! Soldering has always intimidated me but your guide makes it look feasible! One thing I'd like to pick your brain about - googling soldering I chanced upon this page on brazing:

http://www.steves-workshop.co.uk/tip...azingindex.htm

Would you consider a fire-brick hearth, as outlined on that page, an essential item? Or does he only need it because he's brazing somewhat larger items (copper pipes and the like)?

[Captain Sci-Fi]

Hi McTodd,

DX doesn't post here anymore.

To answer your question, getting everything to the right temperature is quite easy, I have a Silverit brazing/soldering torch which runs from a Propane cylinder, it is excellent at heating a large area. Sometimes this is not desirable and I only really use it in bigger applications. For Eagle Brass tube work you really only need to heat one joint at a time so a large electric iron or a small blow torch is ideal, bricks and blankets are really only used for very high temperature "silver" solder and brazes.

You will find that making one joint is relatively easy, when you have to make several close together you will need a jig of some description to hold the parts while the solder runs and solidifies, it won't have any mechanical strength until cooled back to a solid.

JoeyB suggested an excellent tip, he uses strips of newspaper soaked in water to protect good joints from excessive heat and help to localise the high temperature.

As with most practical skills, you need three P's
Practise,
Patience
Persistence.

Good luck and remember to post pictures so others can learn and help you.

[Eaglelover]

Man this is great! Keep this thread!

[DX-SFX]

I'll try and expand it tomorrow with some more photos.

Meanwhile a few additional points:

I rather dismissed electric soldering irons but they do have the odd use, mostly for hole filling. My preference is still for one of the 100W pistol grip type as anything smaller really doesn't have much use for anything other than electronics and wiring. If you find you've got a small area of a joint that hasn't quite filled but is otherwise good quality, rather than risking messing it up by reheating with a gas torch, you can effectively fill the hole with the iron. Flux the area as before and then melt a small amount of solder onto the iron tip. Keep the trigger pressed so the solder really heats up and then touch to the area where the hole is. The solder is usually hot enough to make the bond and fill the hole but will freeze almost immediately as the heat is rapidly lost. You're left with a slightly lumpy carbuncle on the joint but you can trim it with a combination of modelling knife and file whereupon you should find the hole is now filled.

You'll also notice in the article that I precut lengths of solder and place them on the fluxed joint. The two advantages to this are that you can accurately control how much solder goes into the joint and also it leaves you with an extra hand free that would otherwise be engaged with feeding solder into the joint. In addition, you'll find that you won't use as much solder this way. There's no reason you can't hand feed straight off the reel and on occasion you may have to but a few moments cutting small lengths of solder for placing either with tweezers or the tip of a knife is worth doing.

Neither should you be put off the use of Multi-Core solder. It has five tiny cores of resin flux running through it but the amount is inconsequential and won't interfere with the plumbers flux. The solder itself is excellent quality.

One of the real tricks, particularly when starting to assemble something is purely taking the time to clamp or secure parts so they can't move when you solder them. I find most parts can be positioned and kept in place merely by leaning other metal objects up against them or even on them. There's nothing more frustrating that have the parts falling apart just as you're about to apply the solder. Taking some time laying the parts out or even cobbling together a simple jig can save you a lot of grief later on.

Finally, don't overheat the joint. Once the joint has reached soldering temperature, you don't need to hold the flame in place all the time. If you do, the flux can burn off and blacken, the solder can start to oxidise and the brass itself start to discolour. If you do get to that stage, clean it all off, re-flux and try again. If the brass starts to glow, you've gone way over the top and indeed you'll soften the brass because you're effectively annealing it. Soft solder melts at around the 185 degrees c. If the brass is glowing, you're in the 800's. You're unlikely to reach that point accidentally soldering a 44" with a small butane torch unless the mass of brass you're soldering is very small but it is easy to go too far with a blow torch. As with all these things, you'll get a feel for it as you do it. You must also give the parts adequate time to cool. Wait until the solder turns a dull silvery grey. It can be deceptive sometimes how long a joint can stay hot so give it time to cool. Blowing on it will speed things up. Avoid plunging hot items in cold water to quench them. The thermal shock can occasional crack the joint because of uneven shrinkage. Expansion is another consideration. When you heat brass it expands so it's advantageous to make the brass only hot enough so the solder may melt and flow. At soft soldering temperatures it's rarely a problem but I built a 'silver soldered' frame once (around the 750 degree c mark) and the damn thing distorted all over the place every time I added a piece. I only persevered with it because I'd gone so far down the road I had to keep going.

[Alpha149]

Thanks for taking the time to share this! For some of us who don't work with metal too often, this is a great guide to push past the fear!

Thanks,

Evan