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Soldering Tips by murrayec

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I was asked a while back to do a tutorial on Sweat Soldering and here it is;-



The first photo shows the majority of items I use for soldering brass, it’s not all, but there is certainly items here you can make do without.


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Main Items;-


Temperature control soldering iron.


Selection of tips for the iron- (note;- keep certain tips for white metal solder only, don’t mix them)


Solders- 180deg, 145deg, and 70deg lead for white metal.


Flux 12% Phospheric Acid & Distilled Water with a dash of Isopro Alcohol.


Soldering board- a piece of MDF with 90deg hardwood shoulder, grid marked out in 10mm squares and integral clamping system- easy to make and very handy.


Aluminium heat sinks, where one needs to control the temp of work the piece.


Many clips, clamps and stuff to hold things- stainless or aluminium is best, it won’t stick. Dinkey hair clips are very handy, slim, cheep and can be easily modified for the job at hand.


Selection of needle files- smear with baby powder ’creates a friction-free layer to reduce the effects of rubbing and chafing’ and only use them for soldering.


Scratch pens- fibreglass, brass, and steel.


Emery paper- selection of grades.


SS dental pick.


Selection of timber sticks to hold items down- lollypop, cocktail, cuticle stick, all have a use- the timber clamps on the soldering board are from lollypops!


Rare earth magnets and a small sheet of steel- good for holding large brass parts down while soldering, but not good letting the steel iron go near-!!


Container of water for washing parts in.




Soldering is hazardous to the modeller’s health, the solders one use have a high lead content, and the phospheric acid fumes are not good, so a well ventilated work area is required. I use a laboratory type extract and filtration system, one expense I felt was a must when working with silver solders on the bigger models.


And remember- Hot!!




This photo shows the work area- keep it simple and clean


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Sweat Soldering


This next photo shows what we are going to solder, the bell-cranks, drive rods, and the upper link rods for one cylinder on my O Gauge project ‘Hibernia’. This job is called laminating, fitting multiple parts together to give scale thickness.


The Hibernia is here;- http://irishrailwaymodeller.com/showthread.php/2346-murrayec-s-Projects?p=47583&viewfull=1#post47583


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Etched parts have a cusp edge and I etched the holes under size, these will be cleaned up after soldering, after soldering the parts are substantially stronger for this work. The edges will be filed down square and holes broached or reamed to size.


Next check for fit- see if the parts will fit each other. Use pins, wire, or cocktail sticks through the holes to check fit, if needs adjust parts as necessary with files n stuff until they fit.


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Next is to clean the parts thoroughly, I use the scratch brushes on a piece of MDF in a lid from a container. Holding the item with sticks, clamps, or tweezers trying not to touch it with fingers- not to contaminate it with greasy paw print.


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The plan is to coat the mating faces with as level a layer of solder I can get, the solder can be cleaned up if needs be with a file, then apply flux to soldered faces, clamp the items together, apply the iron again until the solder melts and sticks the lamination. Remember to that metal clamps will act as heat sinks so use timber if possible.


So next, set-up the parts for soldering, have the appropriate face facing up, held somehow or a tool at hand for this. The appropriate solder- these parts I call two-stage soldering items, they’ll be soldered now but may have items soldered to them later, this calls for 180deg solder now and setting the solder iron at 200-300deg, later I can then solder with 145deg at 150-200deg setting on the iron without the laminations falling apart. I use a small round bit on the iron for this, as the parts are quite small and will take the solder quite quick. Don’t forget to have the water-dampened sponge to wipe the iron tip on, regularly.


Apply the flux with a small paint brush to the items generously, trying not to flood the holes with flux- the solder will run to where the flux is, so one does not want to fill the holes if possible. The holes on these parts are tiny so they will fill anyway.


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Next we first give the iron tip a clean- stick it in the flux for a sec and wipe off on the damp sponge, then apply a small blob of 180deg solder to the iron tip and put the iron tip to the parts, lay the iron tip on it’s side on the work, the heat will run through the solder into the brass and the solder will run anywhere the flux is, the flux will hiss like mad as it burns off. Hold it there for a while, while the part heats up and then the solder will flow. When the solder is running move the iron tip along the part and try and get it level. If more solder needs to be applied remove the iron tip and apply another blob of solder and put it back on the work. Use the iron to apply the solder; don’t feed solder in from the wire to the work.


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Leave to cool down, give them a good wash in water- no paw prints. Always wash the parts at each stage, don't leave soldered parts unwashed the flux will keep eating away at the it. Clean up the solder if required, we want it to be roughly level- no big blobs and the like.


Next apply flux to the soldered faces, try not to get flux on the exposed faces, as in the like of the Bell-cranks we don’t want solder on the outside spoiling the 3D quality and would be a nightmare to clean up.


If things go wrong and one need to start again- flux the work, apply a small blob to the iron tip, apply the iron to the work and when the solder melts use the scratch brush with extended bristles to flick the solder off the work. Clean up with files and emery paper, scratch pen and start again. I also use a solder sucker to do this, but the nozzle is large on these and they cannot get in everywhere, but are fine on flat stuff. The clamps on the soldering board are great for holding stuff while doing this- a third hand.


Once the parts are fluxed bring them together and clamp them in position. Use pins and sticks to line them up through the holes as done before to check fit. If the holes are blocked with solder, remove with drill bit in a pin vice by hand. Check the edges are flush and clamp it, and then grab the iron, wipe the tip in the sponge, solder blob it and put it to the clamped work. With these small parts running the iron tip along the edge with the solder melting and running in the join does the job- when the solder melts it shows a lovely shiny silver surface, watch that move along with the iron tip. Re solder blob the iron tip if needs be, going the whole way round the work edge until- it’s done, sweated together!


SS-08 IMAG1400.jpg


If you apply the iron tip with solder to the work and nothing happens do add more flux, again careful not to flood holes or detail on the parts. After a while you will notice one is getting it right, flux in the right place, right size of solder blob, apply the iron tip in the right place- wham a silver streak runs through the work only where the flux was placed- Expert!


Try not to apply to much solder this time, one just needs enough for the heat transfer through the solder on the iron tip to melt the solder in the laminate. Also too much solder may flow out onto a surface we don’t want it to. Another option for heating the parts to sweat them together is with a small blowtorch, using a long metal tweezers to clamp and hold the work in the flame until the solder melts and runs.


SS-10 IMAG1401.jpg


That part is done and needs a good clean in water with washing soda, and then it just needs the edge cusps to be removed, edges squared, and the holes to be set to size.


See the edges are filled, the solder is in between the cusps of the two laminates


SS-09 IMAG1404.jpg


When working on soldering the most important thing is to regularly clean the iron tip, the transfer of heat is through the solder contact with the tip and the work; a dirty iron tip will insulate the heat from the solder, as will a dirty work piece, that’s what the flux is for. The solder blob will not stick to it and there is no chance or a messy chance that the solder will run in the work- blobs everywhere and lots of cleaning up to do.


A soldering board is a very handy thing;- it gives a raised level to work on, this allows one to lay the iron on its side without obstruction of your hand, higher is better. Using a board or a block of timber allows the work to be moved around for access- nothing worse that joy-rigging the work on the bench and then realising one cannot get at the joint to be soldered, on a board one can just spin it around. Also having a 90deg shoulder is a handy must for soldering.


Clean all tools and items used – the flux is active for a long time!


The next photos are the other parts going together;-


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and last a shot of the laminated parts soldering complete


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In case you are wondering- the sheet under the parts is an off cut from a kitchen Fry Sheet- takes the heat and nothing sticks to it!


Hope this helps



Edited by murrayec
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  • 2 years later...

Soldering A 2 Axle Bogie Frame.


This is how I solder up a brass 2 axle bogie frame from my home etches for the DART, the same techniques can be applied to most commercially etched bogies and even used for soldering kits!


The units are cut from the sheet with a sharp scalpel and the fold lines are cleaned up with a fibre pen. Some of the half etched fold lines are a bit lumpy- a product of home etching, so I clean the lines out with a small triangular file. The cusp from the etch process is also removed from the edges

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Next the units are folded up, I use Hold n Fold and the like to keep all nice and square. Generally kits are folded with the half etch line to the inside of the fold unless otherwise stated. Use an engineers square and square metal bars to do and check the folds are at 90 deg.

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All folded and ready for some solder, my soldering board is very handy for this process, I use the 180 deg solder, phorspheric flux, set the solder station to 400deg and use a small tip on the iron. Bogies need to be well soldered, they take a bit of bashing so a good fillet of solder is required on the frame folds, most of the joins are not seen so I lump it on!

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Always keep in mind- the heat travels through the solder! the solder will flow where the flux is, and keep the iron tip clean all the time


These are the bogie side outrigger parts clamped down, a good bit of flux is applied

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This is the angle of attack- low with a good blob of solder on, lay it into the flux with the iron touching both sides of the angle and hold it there, a mad hiss and spatter and then the solder flows all over, move the iron tip along the join to ensure a nice fillet develops and then remove the tip

SS-26 IMAG3306.jpg


Nice fillets of solder will reinforce the fold

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Same approach with the frames, loads of flux, a good blob of solder, low angle of attack, when the solder flows after the big flux hiss move the tip along the fold to ensure the good fillet- the molten solder will follow the heat as long as the tip is not removed

SS-28 IMAG3293.jpg


SS-29 IMAG3309.jpg


SS-30 IMAG3294.jpg

Edited by murrayec
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Soldering the corners requires a bit of pressure to keep the brass in place, this is where the board with upstand comes into play, the angle of attack with the iron is still low in relation to the metal- flux the join, a good blob of solder on the iron, stick it in, hiss, flow, hold it there for a few secs ensuring the iron is against both sides of the corner.This join can be problematic, if so I reflux, add a small blob of solder to the iron and go at it again

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I use press buttons to attach the bogies to the chassis, so this goes on next. The hole may need opening out and I use a broach to do that until the button sits down level on the top of the bogie frame, then it's clamped down and away with the soldering

SS-32 IMAG3295.jpg


Again plenty of flux, a low angle with the iron touching the brass and the side of the button, hiss, flow, move the tip around the button and the molten solder will follow the heat, I add a bit more solder in this process to the iron tip without removing the iron from the metal. The soldering board is again handy here- that it can be rotated on the bench to finish the join

SS-33 IMAG3317.jpg


The outriggers going on, held with a stick- there is a limit to what my fingers can take! These are held, fluxed, soldered at one end, then the iron is placed at the other end and the solder flows towards the heat. This has to be done quickly keeping in mind that there is a soldered fillet underneath that I don't want melting and falling off

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Waisted pin point wheel bearings next, the holes need to be opened out for them to fit and I use the broach again to do this. I use a wheel set to hold the bearings in place for soldering. Flux, blob of solder on the iron, and a quick touch against the bearing and frame, hiss.....

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and done

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after a really good clean with water and toothbrush, one done

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and all done, a set of bogie frames for a DART that need a bit of cleaning up and some blackening

SS-40 IMAG3318.jpg



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.....and the bit missing from the sequence above;-


The connection plate to the chassis, again etched brass folded up and soldered as above, the half etched circle on the plate holds the button on centre while clamped and soldered- then the assembly is clamped and soldered to the chassis

SS-41 IMAG3322.jpg



Edited by murrayec
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