brass

Maybe - but what have you tried? In detail please - materials, pretreatment, method etc.

Brass is usually pretty easy to solder, so you are most likely doing something wrong. It's probably better to find out what, than to try new techniques.

-- Peter Fairbrother

Do you refer to soft or hard solder? Is the solder not melting or is it not penetrating the joint? Are you using an iron or a blowlamp? A little more detail might elicit helpful answers.

Cliff.

No! That's how to get a dry joint.

Heat joint with iron, then apply solder to joint, NOT to iron.

-- Peter Fairbrother

Rules for successful soft-soldering;

1. Metal must be scrupulously clean.
2. Use Bakers soldering fluid to flux the joint.
3. Use a soldering iron of the right wattage. Too small and solder will not melt immediately, which it should.
4. I personally use a small pen torch for jobs like this.
5. You must get the solder nice and fluid very quickly.
6. If using an iron, clean tip of bit with an old smoothish file, dip in the flux and immediately apply solder to "tin" the iron.
7. Pick up a small amount of solder on tip of iron and apply to joint. Hold for a second or two till solder flows into joint.
8. Wash off to remove corrosive residue. Calor used to supply small jars of solder/flux paste which is ideal for jobs like this. tom

The reason for this is that if the solder is melted on the workpiece then the workpiece is definitely hot enough - if it is melted on the iron, the workpiece may not be hot enough.

Usually the thickest part of the workpiece is the last part to get hot enough, so melt the solder on that.

-- Peter Fairbrother

1. Leaded solder is easier to work with than lead-free.

Clean as in no oxidation, paint or other crap, but in particular, it must be free from grease (including finger prints), so wipe it over with meths, IPA or acetone just before soldering.

Baker's is good, but any flux for plumbing or electrical work will do for brass. e.g. La-co, Fry's powerflow, Fluxite, Multicore, etc.

Agreed

Agreed.

No, If the soldering-iron tip is coated (with Iron, confusingly) then you will file the coating off, which is bad.

You can clean the tip by wiping it on a bit of damp cotton rag.

After you have wiped the tip dry, immediately tin the tip with a little flux-cored solder. Aim to then do the joint immediately, before the flux burns off the soldering iron tip.

No, after cleaning and tinning the tip, immediately apply the soldering iron to the joint. Then apply the solder directly to the juncture between the soldering iron tip and the joint.

Peter, although that is good advice for soldering electronic circuits, it is not best practice for soldering chunks of brass. The heat transfer from a dry iron is relatively poor, and the brass will conduct the heat away too quickly; unless you have a massive iron, the solder will take ages to melt (or may never melt) and the metal will rapidly tarnish and become unwettable.

If you doubt me, ask anyone who regularly makes etched brass models. Putting some solder on the iron tip drastically increases heat transfer and hence speed of making the joint.

I find in that work most of the time is spent cleaning off unwanted solder. It is often better to tin the metal to be joined and sweat it together, or to use a resistance soldering unit.

David

There's the rub. A massive iron is the correct tool for the job.

When tinsmithing eg 2mm brass sheet, you need an iron which weighs about

1lb. For 1mm sheet, at least 6 ounces. And more now, if leaded solder isn't used.

Tinsmiths irons typically started at about 4 ounces, and they were working with tinned steel - thinner than 1mm, and less conductive than brass.

You might think that a tinsmiths iron was that weight for it's total heat capacity, and that that wouldn't matter now as an iron is continuously heated electrically rather than intermittently heated in a firepot, but consider -

- let's say you want to solder some 1mm brass sheet. You have to heat say 1 cm^2 of brass by 300 degrees, that's 990 joules. You want this delivered in say 2 seconds, that's 500 watts. Give yourself a decent edge, and you need to be able to deliver 1 kW for 2 seconds - to be able to solder 1mm brass.

Now you could use a lightweight 1 kW temperature controlled iron for 1mm brass, but I don't think many etched brass modellers do. So they have to rely on the iron holding maybe 2,000 joules of deliverable heat, which means the iron heats up when unused and cools rapidly when applied.

Now when the iron is at it's hottest it can't be too hot or you start getting corrosion problems, and when it's delivered it's heat load it'll still be hotter than the joint - even copper doesn't transfer heat immediately. Together these mean that the cooling of the iron as it's applied can't be more than 100 K, and 50 K is better.

2,000 joules of heat deliverable in 2 seconds is about equivalent to 4,000 joules at 50K iron tip differential, which means the iron should weigh 200 grams, or 8 ounces - for 1mm brass sheet.

I have used the let-the-solder-do-the-heat-transfer technique when proper equipment was unavailable, but it's suboptimal.

Let me explain why in more detail later though, dinner calls.

Yep. Tippex is good, both for soldering and brazing - paint it on and the spelter doesn't wet the metal.

-- Peter Fairbrother

I have tried hard and soft solder. I have tried a light and heavy electric iron. Parts are spotless and flux was applied. The solder is melting but not joining 2 parts together. I use blue tac to hold parts onto a soldering mat. Ray.

It's impossible to hard (silver) solder with an iron so I wonder what you have been using. Some possiblities for you to consider are:

- the parts are not brass,

- your are getting them too hot and scorching the flux,

- the parts are not clean,

- the oily component of Blue Tac is contaminating the joint.

I suspect the most likely problem, if you are familiar with soldering, is the Blue Tac.

Cliff.

In the pub the other night we were discussing the difficulty of soldering up petrol tanks from vintage cars. The heat soak away is huge and so the problem is similar. One of the group had a simple solution that had worked very well for him. He preheats the area to be soldered with a heat gun an bingo the solder flows a treat. Needless to say he uses a BIG iron as well. Haven't tried it my self yet but I'm sure it works - it makes such sense.

My suggestion is to use a resistance soldering kit if you can borrow one from a member of a local model railway or engineering club as they are no longer sold in the UK / Europe because of tighter H&S regs. Although it is usually talked about with regard to making brass railway kits, I have used one for soldering guite thick pieces of brass and nickel silver. The localised very high tempeature gives you the ability to have soldered joints close together with little chance of desoldering the next joint.

Here is a link to its use in model making:

It is possible to make your own using a transformer that can deliver a high current at low voltage eg from Maplins* and there have been instructions posted on the net eg

*Unfortuntely Maplins no longer seem to do the 100VA transformer kit which people had used as a basis for their home made RS unit.

Alan

It is some years since I have dismantled primary batteries for their carbon rods; what would I find nowadays if I were to dismantle alkaline cells? Is "alkaline" a veiled reference to the sal-ammoniac of carbon-zinc cells, or is there some other material forming the positive terminal?

In article , Alan Dawes writes

Alan,

Most of the RSUs did indeed disappear from the market because of the CE regulations a few years ago. However, I have heard that Swanage Model Co have recently re-introduced theirs.

They don't appear to have a website, but contact details are 20 Anglebury Avenue, Swanage, BH19 1QP, 01929 424650. Price a year ago was £139.50 plus £10 postage, spare tips £2.00 + £1.00 p&p for 5.

I have one of these units and find it invaluable for kit building.

David

In article , Magnum writes

No, I think the alkaline electrolyte in alkaline manganese cells is something a good deal more corrosive than the sal ammoniac (ammonium chloride) in zinc chloride cells. If you do try messing with it, take great care.

See my other post for details about where to get the graphite electrodes.

David

There are three main types of domestic primary cell, zinc-carbon (very cheap), zinc chloride ("heavy duty"), and alkaline.

All three work by the reaction between manganese dioxide and zinc, the main chemical difference is the electrolyte, which doesn't get used up - ammonium chloride aka sal-ammoniac for zinc-carbon, zinc chloride for zinc chloride, and potassium hydroxide for alkaline.

Potassium hydroxide is very nasty, it's caustic, dissolves the fats in your skin and turns them to soap, and so on - so don't take alkaline cells apart!

Also, while zinc-carbon and zinc chloride cells have carbon rods in the middle, alkaline cells don't - they are built the other way around, with the zinc in the middle rather than on the outside.

That's why alkaline cells have the insulating gap on the bottom, not the top, and it's also why they leak from the bottom - though they don't leak nearly as often, when they do they leak potassium hydroxide, so be careful of leaking alkaline batteries.

It also means that unlike a zinc-carbon or zinc chloride cell the cylindrical body of the cell is connected to the positive terminal - this could cause problems for some equipment, so the insulation on the outside of an alkaline cell is made to be much tougher than usual.

Once you have recovered the carbon rods they will have some ammonium or zinc chloride in them, but that doesn't matter as far as using them for soldering goes - both are used in fluxes.

As far as disposal of the bits goes, retailers who sell more than 30 kg of batteries per year are required to accept batteries for disposal, and they then have to be disposed of as hazardous waste - which is completely pointless in my view.

Some batteries are environmentally unfriendly, containing lead, mercury and cadmium, but most zinc-carbon, zinc chloride and alkaline batteries don't contain any of these (and completely banning mercury in all batteries, which should have been done years ago, would mean none of them did).

You aren't supposed to put them in domestic waste, but it's not illegal to do so (though some newspapers etc have reported otherwise).

-- Peter Fairbrother

In article , Peter Fairbrother writes

I originally intended to wait to see your follow-up, but as this is really a separate point:

Your figures (assuming you meant 1 cm^3 of brass) look about right, but

(a) If you need to heat the joint up by 300K, you maybe need to reconsider which solder you are using, at least for delicate modelling work. I do most of mine with 145 degree solder, with 179 degree if I know it needs re-heating. I do have some 280-odd degree stuff but it never gets used.

(b) More seriously, your model does not take thermal resistance into account. This gives rise to a slower heating rate and thus a greater risk of oxidation of the metal.

(c) I can't really see most people getting on too well using an iron the size you suggest to solder a 3mm lamp iron onto a loco smokebox, or other small detail, or indeed larger stuff in awkward corners. I know mine (a 50W TC iron) is much smaller than this - I often wish it had more heat capacity, but not if it meant making it bigger (yes, I know it's a trade-off).

David

Good to know that there is at least one source of carbon rods for an RS Unit is still avalable. About 18 months ago I was able to get a couple of spares for my 12 year old London Road Models RS unit from a model show in St. Albans.

Doing a bit more googling has come up with the suggestion that suitable carbon rods are available from suppliers of welding equipment.

There's a recent thread about RS units here:

using an old car battery charger.

Alan

I couldn't see any details of the carbon rods dimensions required but these guys used to be able to supply a list, .XLS actually, of graphite seconds

. If the grade required is important then enquiring would be required as the last time I looked at the list the grade was not specified and it wasn't possible to determine it from the details.

If approx 16mm diameter x 305mm long would do then I have some graphite rods spare.

At a welding supplier you may want to ask for carbon arc brazing electrodes.

Peter, I picture each of these joints as rather small - 1mm and 2mm brass, and will not require much heating up. Applyng the solder as I said creates a quick heatpathand will never give a dry joint. and also minimises the amount of solder applied, for a neat job. The first soldering job I ever did was to make up bird cage fronts for my father

- an almost identical job, when I was eleven years old. I have been soldering for another 73 years since, and taught soldering for over thirty of them. I used to make the fuel tanks for tether cars for the late Miguel de Rncougne, if you have heard of him. I think your method is more likely to create a dry joint. If I were to do this job, after initial preparation, and setting up, I would probably wind a coil of multicore fine solder, and slice along to give liitle palins of solder. These could be closed around each joint, then wafted close to the joints with the tip of the flame of a small pen torch to give perfect joint with no surplus. Tom Oliver.