Do I need Flux

[Geoffrey-370803]

Hi all,

firstly, sorry if this seems a silly question or is repeated.

I am a decrepit old fogey returning to model trains after, nigh on, 58 years. I have recently started to build my first (and probably last) layout. The problem I have is, I am also new to soldering and through watch a myriad of tips via YouTube vids I have now become confused and somewhat anxious.

I understand that to achieve good soldering outcomes I should use flux. Now, here is my concern. I have started to use Baker’s Fluid No. 3, which did improve my results BUT I have since seen a vid from a modeller and an article from DCC concepts which state that this product is very harmful to Nickel Silver tracks. Is this correct and if so, what is the most suitable flux to use.

thanks in anticipation.

[Rallymatt]

If you go to the main discussion area and find the stickies at the top, there are excellent guides to all manner of general model railway projects, including soldering that applies across all scales. Well worth a good read 👍

[Brew Man]

If you use pre-fluxed solder, (readily obtainable) there is no need to add more. What's very important though is to make sure both surfaces to be soldered are really clean, otherwise you'll have trouble making the solder stick. Oh, and good luck with your return to the hobby. I returned after a similar time gap.

[96RAF]

I use resin cored lead solder and never needed separate flux. Most fluxes need to be washed off to neutralise them which is nuts if dealing with electronics.

[Flashbang]

Ah, the 'Black Art' of soldering! Actually, it's not a Black Art at all. But you do need to be aware of several things.

I do not recommend using Lead Free solder! Instead, look for lead content resin cord solder, usually referred to as 60/40 Tin/Lead. Lead free solder requires a much higher iron temperature to melt correctly which many domestic irons and particularly older ones can't quite reach. 60/40 solder is readily available online and in some electrical stores.

You normally do not need any flux. Its already built into the solder. Never use acid based flux for electrical work, as acid flux has to be washed off once soldering is completed and that is not possible with electrical soldering work! There are some flux compounds sold specifically for electrical soldering DCC Concepts and Carrs sell them but generally you really don't need them!

Ensure your soldering iron tip is in 100% good condition. If its pitted or black either replace the tip if that's possible or obtain a new iron. Use a damp sponge to wipe a hot irons tip onto to remove previous solder residue. A tip reviver (Brass shavings in a small pot) will also help. But if the tip is really bad then replace the tip or iron. Use a soldering iron with at least a 25 watt element or higher wattage. Fitted with a tip that's ideally about 1.5 to 2.5mm across. Or is a pointed tip.

Allow the iron to reach its working temperature. Turn it on and keep it safe, ideally in a special soldering iron safety stand. Then wait for 5 minutes. Once time has passed the tip should be at the optimum temperature. Apply a little 60/40 solder to the tip and then wipe off that solder on the damp sponge (The sponge is damp not wringing wet!).

Ensure the items to be soldered are spotlessly clean. A fibre pencil is ideal for scrubbing the rail clean - Even brand-new rail should be cleaned! However, you can use a small piece of fine Emery cloth or even the blade of a craft knife to scrape the area to be soldered.

Once both items are cleaned, coat the irons tip in 60/40 solder and then place the tip onto the area where soldering is to take place. Allow a couple of seconds for heat to transfer then feed in a little of the cored 60/40 solder onto the heated area with the iron still in place the solder should flow onto the heated item. Remove iron, wipe tip and recoat and apply solder to the other item (usually the stripped end of a wire). Wipe tip again and apply a little more solder to its tip, then place wire onto the previously coated rail and apply the irons tip onto the two. Allow a couple of seconds for the heat to melt both solders and if necessary apply a little more solder with the tip still in place. Once the solder is seen to melt and form a liquid all around the joint, remove iron and hold the wire still until the solder solidifies - usually within 5 seconds. Wipe tip and replace in safety stand. Job Done. But do thoroughly wash your hands after soldering work is completed where lead content solder is used. :-)

Edit to correct typo spelling error!

[ntpntpntp]

I think Bakers Fluid #3 is for soldering copper pipes and similar "industrial applications". Not really suitable or necessary for typical model railway soldering of wiring etc.

As others have said, flux-cored electrician's tin/lead solder and appropriate technique is all you need for most work. That said I keep a small pot of Fry's Powerflow which comes in handy for things such as soldering rail to brass screws at baseboard joints. Just the tiniest amount on the tip of a cocktail stick to ease the flow. I know Powerflow is sold for use with lead-free solder but I use it with my tin/lead stuff (not a fan of lead-free solder).

[david_watts1]

Always use flux even with prefluxed solder, it makes life so much easier. The type is up to you, I'm still using stuff I probably got from B&Q 40 years ago.

[ColinB]

I will comment on my experience. If you are soldering connections to a PCB or a motor generally solder containing flux is perfectly ok. If you are soldering to track I found using flux the solder flows quicker which avoids the plastic sleepers underneath the rail from melting, without the flux it seems to take longer for the solder to melt even with the flux impregnated solder. Finally if you are doing fine soldering like a surface mounted component to a PCB we found that you need special flux, but I doubt most people will be soldering microprocessors to printed circuit boards (PCB). If you think about it, flux stops oxide forming so if it only flows when the solder melts, the job has already oxidised so a separate application of flux avoids this. Bakers fluid is what I used to use on motorbike cables to solder so I imagine it must contain flux, if I remember rightly it is liquid rather than a paste, so probably not that suitable as to it attacking nickel silver I imagine it is acidic to clean up the joint but you won't be using that much, but it is more practical to use flux.

[Silver Fox 17]

Bakers flux, real name is Zinc Chloride but sometimes referred to as "killed spirits" is based around Hydrochloric acid and as others have mentioned should never be used on anything electrical. I use it for etched kits but that is all.

For any other work I use a non corrosive flux and what I have is what we called "electricians flux" at the railway. Its trade name is Coroline and I always use it for everything else. I never rely on the multicored flux as that can often dissipate before a joint is completed. A tiny smear of this is all that is needed, it can leave a residue but non harmful and easily cleaned with a paper towel or if left too long meths or white spirit. Most times if such a small amount is used you wont notice it.

[Geoffrey-370803]

Thanks everyone for all these great responses. I shall look for the other threads.

I did solder most of my droppers without flux and the results looked awful. Fortunately I put them under the rails so they don’t show. I joined a couple of flexi track using fishplate and solder on the outside of the rail, using the liquid flux, ( taking the advice from other threads and YouTube) and the aesthetic was better, though one did part when I was bending it (5th rad curve). I actually found it easier to join after bending.

now, if only Hornby would get so TT120 rail joiners in stock! I’m stabbing my finger to shreds trying to fit Peco on to Hornby set track. Suppose I will have to pay as much in postage to get one of those proprietary widgets for the job.

thanks again. It’s lovely to know that people with experience are willing to help newbies.

[Rallymatt]

Look for some code 80 rail joiners from other TT:120 manufacturers, Tillig, Piko, Roco etc they will fit Hornby TT:120 track perfectly

[Fishmanoz]

https://uk.hornby.com/community/forum/faq-how-to-solder-for-model-railways

[ntpntpntp]

| @geoffrey-370803

| I’m stabbing my finger to shreds trying to fit Peco on to Hornby set track.

Forget trying to use Peco joiners with Hornby rail, as discussed on other threads they don't fit as the Hornby rail has a wider foot than Peco rail.