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SOLDERING INFORMATION & ADVICE #3 |
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The Black Art de-mystified
Part 3a: Whitemetal and specialised soldering. Soldering whitemetal is easier than you think! Part 3b: The harder metals YOU can solder even stainless steel if you must Part 3c: Producing a clean finish A properly cleaned up job makes for a better result ——————————————————————————————————— Whitemetal and specialised soldering. Soldering has gained a reputation as a “black art” to many modellers…. Not because it IS hard but because of three simple things: poor preparation, inadequate equipment and incorrect materials. In fact, there are very few of the metals we use in modelling that cannot be soldered properly and quite easily providing we use the right equipment… develop a couple of simple skills and proceed with the task methodically. There are TWO key factors that make the difference: Cleanliness: We are not talking simply dirt free, but oxide free. Most of the “hard to solder” materials are that way because they oxidize very quickly OR because their often quite hard to see oxide layers are hard and act as a barrier to prevent the formation of the necessary inter-molecular bond between solder and metal layers. This can be achieved without stress with cleaning tools AND the right flux. Inadequate heat delivery: Temperature and heat are NOT the same. It doesn’t matter how high or low the temperature of your Iron can be set – it’s the ability of the Iron to deliver adequate heat to the joint as a rate which can both activate the flux, melt the solder and encourage the joint to form before the flux is burned off or evaporated, before the oxide layer re-forms and before the heat applied has leached into the metal and weaken or damaged adjacent parts. If we can fix THESE things, and teach you a couple of simple soldering methods, then YOU can solder almost anything to anything – and create almost ANYTHING you wish for your modelling. ————————————————————————————————————————- Soldering common but normally incompatible metals: Sometimes, we need to solder one item to another, yet the solder needed for metal “A” will not work with metal “B”. The most common occurrence here is soldering whitemetal to brass. We need to use a “low temperature” solder for the whitemetal BUT this will not stick to Brass. SOLUTION: TIN THE BRASS FIRST (Use Carrs 188 or DCCconcepts 179 solder + DCCconcepts Sapphire Flux OR Carrs Yellow or Green fluxes). Clean the brass to be “tinned” and then use lots of flux and only a very little solder, flowing it out with the tip until it’s a thin “plating” on the brass. Don’t dawdle too long and keep the tip moving. Clean up if needed with a fiberglass brush used “soft” (That means with appx 1cm exposed). LOWER the Iron temperature for whitemetal use (I like it as about 200 degrees centigrade) and clean any excess solder off the bit. Position the whitemetal part and add a big brush-load of flux so it fills the spaces between whitemetal and tinned brass Take up a small amount of whitemetal on the Iron tip… and apply to the joint. The solder should “Suck in” to the joint. If needed, re-flux and apply more solder (Just enough – too much is hard to remove tidily. Joint looking clean / Job done! Joint still not smooth? Re-flux and run a clean Iron tip over the joint. Excess solder will be drawn in. If any excess remains, dip some solder wick into the flux and hold it on the seam. Place the Iron on the wick and run it along the joint. Excess solder will be drawn in and removed by the wick. When the soldering session is over, WASH the model with attention to the joint areas. Ammonia in water OR any alkaline solution (a little washing soda in water is good) to remove and neutralize the remaining flux residues if you sue carrs, or Meths and water if you use DCCconcepts Sapphire Flux. An old toothbrush, OR a for the tool freaks among us a dedicated battery toothbrush are both useful cleaning tools. This SAME technique can be used when soldering ANY incompatible metals, Copper Brass & NS to Zamac or Alloys are good examples. NOTE: Don’t use for electrical connections to cast metal: Sometimes screw fixing is best! ————————————————————————————————————————- The harder metals: Soldering supposedly “difficult to Solder” metals: Depending who you talk to, Brass & NS can be classed as easy or hard, but personally I find it’s a simple task to do either well. You will too. Certainly, brass rod or NS is much easier than some forms of sheet in the same material and castings of any metal are ALWAYS harder then soldering processed metal such as rod/profiles or sheets. The Brass used in etched kits or K&S metals shapes is usually good to solder. SOLDERING BRASS Nickel Silver or STEEL:
A nice example of cleanly soldering brass, nickel silver and whitemetal to themselves, and to each other! This locomotive is being built in 4mm scale (A - Spot Soldering) Clean up any cusp left over from the etching process OR any dags from cutting. On castings, remove flash and clean up mould part lines if present Clean the areas to be soldered with wet and dry (600 grit +), a Carrs/DCCconcepts cleaning block or a fiberglass eraser. Check the Iron is set to the right temperature and has the appropriate bit in place. Protect any adjacent joints that are very close if needed. I find a wad of wet loo paper is a VERY effective heat sink and works wonders as an easy to use protection that easily conforms to all shapes and won’t harm fine detail. Place the parts in position, making sure you can hold them without burned fingers as the heat travels quickly... Apply flux (Carrs Orange if it can’t be cleaned up later, or DCCconcepts Sapphire Flux, Carrs Green or Carrs Yellow if it can). For STEEL I recommend Carrs Orange or DCCconcepts Sapphire Flux only as they are non-acid. Take a SMALL amount of solder onto the tip of the Iron. Apply the Iron to the joint area. Do NOT press down on it (pressure won’t help and will damage the Soldering Iron bit OR the model) Work the solder smoothly into the joint if needed by gently moving the tip along the joint Remove the Iron. (B - Seam Soldering) As above in all general areas, however you MAY find it helpful to take steps as follows: Make sure the parts fit well along the whole length of the seam with no gaps. File or gently bend the material to accommodate any irregularities. Check carefully. Solder is an effective filler on some occasions BUT care in preparation WILL make a difference. I do not usually bother UNLESS it is a difficult seam such as a right angle joint in very thin material at the front of a Belpaire firebox etc, however TINNING can be helpful in ensuring a strong bond first time. Tin only the areas that will be soldered and make a very, very thin tinning layer. (If you make the layer very thin any excess will easily buff off with a fiberglass brush and become invisible.) If there is space and easy access, work from the back initially for this by “Spot” soldering. Flux and “Spot Solder” in several places. This allows you to check alignment before soldering the whole seam. Adjust if needed. Re-flux generously along the whole joint. Add just a little solder to the tip and (again from the back if possible) with the tip touching BOTH bits of material, run the Iron slowly, gently and steadily along the seam. When solder runs out add a little more to the tip and repeat fluxing and flowing the solder onto the joint. If the flux evaporates away with Iron heat add more. Do NOT linger too long in one place and overheat the brass. Do NOT press hard with the Iron at any time. Excess Solder on seams: Use the de-soldering braid soaked in flux. Place on the seam and run along the seam with the Iron on top of it to pick up excess. SOLDERING SPRING STEEL AND STAINLESS STEEL: Techniques as above with Iron at high temperature using a largish chisel type bit that will transfer heat properly. Use Carrs Black label flux or DCCconcepts Sapphire Flux. Perfect cleaning is essential. Tinning with 179 degree solder (containing silver) will help a good joint, and once tinned you will be able to solder almost any solderable material to the Stainless steel. For larger jobs you should consider using a small torch type Iron. SOLDERING ALLOYS and DIE-CAST (Most): Use a strong Iron as good heat is essential. Use Carrs GRAY label flux. Handle with care – it is VERY aggressive in order to strip the hard to clean oxides that form immediately on Aluminium and similar metals. TIN the Aluminium with DCCconcepts or Carrs 179 Solder You can now solder almost any other solderable material to the Aluminium as the tinned coating will “take” with normal solders. IMPORTANT: Joints made to Aluminium will become brittle if they are exposed to air. As soon as possible, clean off any flux residue thoroughly, tidy up the joint as needed and apply a coat of primer to the area that has been soldered. This will “fix” the state of the joint and it will remain strong and firm. Soldering close to other soldered joints I solder everything on a loco kit, from major parts through to tiny things like handrail knobs. That means that I’m soldering parts to other parts that have also been soldered…. Yet, I almost never have a problem with heat causing one detail to drop off as I solder another to the model. There are TWO easy ways to do this. (A) Use a “step solder” process. This means utilizing a series of solders which melts at different temperatures. (See the solder range in the attached sheets) Solder major components together with a higher temperature solder Add details using lower temp solder such as 179 or 145 detailing solder (B) Use “heat-Sinks” These can be ANY practical thing you can find that be placed on or clipped to the work between soldered parts to absorb the heat from the second joint. Ie: Special alloy clips designed for the purpose “Dolly Grips” – Older style hairdressing clips for holding rollers in hair (easily bent and shaped – aluminium alloy clips) Metal bulldog clips Pliers and forceps/medical clamps A bit of alloy held on with a clothes peg A lump of metal simply held by its own weight But my favourite… and MOST often used??? A bit of wet LOO PAPER, a cotton wool ball or TISSUE – almost wet enough to drip but not quite – squeezed together and placed on the area I want to protect. This works every time if it can be applied to the area… and you can even see it working as the water boils off, showing you just how effective it is being! ——————————————————————————————————————————-- Cleaning up & removing excess solder There are two parts to the cleanup: dealing with excess solder and removing active chemicals from the project at the end of every work session: KEEPING IT TIDY: We CAN of course always chip away at it, but the easiest way to get rid of excess solder is to use the right technique and never have it there in the first place. Remember that the ONLY part of the solder that contributes to the joint strength is in fact the bit that makes contact with the metal… all the other solder we add is really only to make us feel better…. And just makes the job look imprecise. Keep blobs inside seams OR avoid them totally. Tinning followed by refluxing and minimal solder is always best if seams need to be tough. Minimising excess solder: * Tin parts with a THIN coat of solder that flows really well, such as 179 or 188, clean up the tinning before assembly, removing excess or sanding smooth if too much has been applied. Then Re-flux and use the absolute minimum solder on the bit (just enough to help heat transfer) to make the final joint. * Work from the rear of every joint if you can. Solder from the front ONLY where some slight gap filling may be needed, and then if possible add solder first to the rear, and ONLY draw it through the work by re-fluxing and then running the Iron along on the visible part of the seam to attract just enough into the joint to make the perfect joint. * Run a bit of flux-soaked de-soldering braid along finished joints to pick up excess and create a smooth seam. Removing Excess solder: Try not to use your new or expensive files – they will soon clog and be rendered useless. If you MUST use a file then either chalk it with dry chalk OR… dip it in a weak solution of ammonia and water first – this will (apparently – I’ve not tried it) reduce clogging or make it easier to get bits of solder out of the teeth. An economical and very effective alternative that is perfect for curved seams is reasonably coarse wet and dry paper (appx 180~240 grit) glued with waterproof glue to a strip of flexible metal or plastic. Vary the width and make a few from very narrow to say 10mm wide. Used wet, (Dip it in water) this will clean off excess VERY well and will also follow the edge of a joint or the curve of a boiler profile beautifully without creating “facets” or flat areas anywhere Take your time and do not skimp on the cleanup. Dip the loco body or wagon etc in a tub of water & detergent (an old ice-cream tub works well) and clean it off regularly so you can see and feel each joint properly. The places that still need work will then stay obvious and you’ll do a better job. Summary of tools that will help: * Use older files dipped in ammonia/water mix or liberally coated with chalk or talcum powder to reduce clogging * Use a broken off scalpel blade or snapped off hacksaw blade or scalpel blade… or even a sharpened screwdriver to tease away excess solder. Use lots of gentle strokes not big pressure to gently pare away any unsightly lumps or square up and sharpen a seam.. * Use De-Soldering braid as above. As an added “TIP”, if you have a long seam, such as between two bits of whitemetal casting that are firebox and boiler, or two say bits of brass that make a seam between tender side and footplate, running a flux soaked desoldering braid back and forth with the iron on top will both remove any excess and give a beautifully smooth and sharp 90 degree angle between the two by removing all solder except that which comprises the bond. Make sure there is lots of flux and stop as soon as its all gone of steamed off. * Use the fiberglass brush set to “HARD” – that means no more than about 5mm showing. It will wear away solder surprisingly fast. * Use wet and dry paper used WET (see tip above) After soldering- surface treatments Solder oxidizes and fluxes + heat make it happen quite fast after the joint is made, so the first and most important rule is to thoroughly clean the project after every work session – and during too if you are using strong active fluxes. HARD TO SOLDER METALS AND ALLOYS: All alloys need a very active flux to get rid of oxides, and this is also true of casting alloys and metals such as stainless or hardened steel alloys. Left in place overnight an active flux can etch the brass or other metal and will certainly start to affect the joint, making it brittle in some cases (depends on flux/solder combination). With certain alloys such as aluminium deterioration sets in quickly so we strongly recommend that you follow this sequence for all jobs involving alloys or die-cast materials which have a high aluminium content like Zamac. Prepare the parts and test fit before you start the job. Prepare not only the alloy parts but ANY parts that will be applied very close to the aluminium. Solder aluminium first, wash it, then immediately solder other parts and dress/clean up all joints, Clean the sub-assembly VERY thoroughly with a neutralizing solution of washing soda and water or ammonia and water, followed by a non-lanolin detergent or scrubbing type cleaner like JIF & an old toothbrush. Rinse VERY thoroughly then wash in hot water and dry with a hair dryer or fan heater. When it is thoroughly dry, and whilst it is still warm to the touch, apply a spray of automotive undercoat. From an aerosol to both seal and protect the alloy joints from any further oxidization. Any areas that still need soldering can easily be cleaned off later with a bit of MEK or other solvent. (when this is done, follow the cleaning & priming routine again) STANDARD METALS AND ALLOYS: Irrespective of material soldered all non-electronic soldering jobs will involve a flux that should be removed. Active fluxes: Use an ammonia and water or washing soda and water mix in an old ice-cream tub on the workbench. If leaving the project for lunch etc or stopping for a short while just drop it in and rinse off. After finishing for the day a thorough clean in this mix with a toothbrush followed by a thorough rinsing under warm water and scrub with Jif /toothbrush will get things clean and shiny ready for the next days work. NON-active fluxes. Use alcohol and water (meths and water or isopropyl alcohol and water) as above for the interim and post work clean, followed by the same scrubbing and rinsing as for active fluxes. ELECTRONICS: and “non-washable” joints such as track & droppers: A basic circuit that’s got grubby can actually be washed in soap and water, providing it is rinsed off thoroughly and dried properly and PROVIDING that it Does NOT have any rotary device such as trimmers or potentiometers, IC sockets, relays or switches mounted to the PCB. For effective and safe partial cleaning Use meths or Isopropyl alcohol and water or a fully evaporating solvent applied with brush, cotton bud or toothbrush. If your budget runs to expensive aerosols then there are some sold as cleaners for PCB’s that will work fine on any PCB or track joint, although they MAY stain adjacent areas if used on a layout... Don’t skimp on this and if you can get to the job without damaging it even clean off “no-clean” fluxes if you can: Its good practice that should become a good habit, as in some cases not doing it may lead to reliability problems long term. A clean job is a good job no matter what the soldering task is. ————————————- Do you still have any other questions about soldering? No problem – just click here to email us and ask, we’ll be happy to help! OK… that’s all on soldering for now. Don’t just sit there, please…. I’ve spent many hours writing these pages and trying to help you… the least you can do is get to it and start on the path towards becoming a soldering expert! You WILL succeed!
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