I have been trying to make railings from 1mm and 2mm brass but cannot get
the joints soldered.
I have tried different solders and different irons. Would a gas flame gun be
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.
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.
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
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 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
I was beginning the follow-up [*] when I thought, maybe we are actually
agreeing furiously?
It all started like this:
>>>> 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.
>>> No! That's how to get a dry joint.
>>> Heat joint with iron, then apply solder to joint, NOT to iron.
>>
>> 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, 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 wasn't trying to suggest that you should use a dry iron, that's plain
silly - yes, you should wet the iron and use the solder on the iron as a
heat transfer medium to get the parts hot.
What I was trying to say is that the solder which makes the joint should
be applied to the joint, and *not* first to the iron.
That way the solder is cooler than the joint when applied, and it won't
melt unless the joint is hot enough, and wet enough, to melt it. Which
means it's almost impossible to get a dry joint.
[*] I may post it anyway, lots of lovely math and numbers :) - but that
sort of thing takes a while to write
but as this is
Wow, is that indium/bismuth based? Usually I use lead (shhh!) or tin
based, but I don't do delicate modelling. Though I used to make bespoke
SMT soldering iron bits in the very early SMT days, including ones for
soldering directly to chips (by hand), so I can do tiny :)
However you will want to heat the metal up to somewhere, say 30 degrees,
above the solder's melting point in order to get good flow etc; call it
maybe 200 degrees for the 179 degree stuff, which works out at about a 6
ounce iron for 1mm brass sheet.
Thermal resistance of the iron is supposed to be in the "is about
equivalent to 4,000 joules at 50K iron tip differential" bit as above,
though I agree it's not clear.
OK, I think you may be right - though in practice there is often enough
solder on the iron to make the joint anyway, and feeding more in would
just add to the mess to clean up. I'm talking about small components
here, or edge joins in 0.018 thou brass. With experience you can
(usually) see whether the solder has wetted the brass, and if in doubt,
a stress test usually finds out one way or the other.
BTW, the 1 cm^3 lump in your example is relatively massive compared with
the thin brass etch stuff - I can't imagine soldering anything to that
cube with my 50W TC iron, would probably use a gas burner.
Look forward to it.
I don't have an analysis, but these things usually have bismuth in them.
It's a very good compromise: it wets brass far better than genuine
low-melt solders (70 deg and 100 deg are readily available, the latter
being a bit stronger) but doesn't require furious heating. With care, it
can even be used on white metal if the latter is not too low in MP. It
is marketed by Carr's in 0.5 kg reels, or by other model suppliers in
smaller amounts at considerably higher unit cost... Let me know if you
would like to try some.
Heavy engineering!
OK, didn't spot that.
I generally try to avoid using a conventional soldering technique on
etched brass - solder cream, RSU or sweating are all preferred according
to circumstances as they all leave less cleaning up to do. The
conventional "run hot iron + solder along seam" approach is still useful
for large butt joints, and you can usually do those from inside where it
doesn't show. (Actually, experts still use an RSU for that, but I
haven't quite got to that level of proficiency yet.)
David
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.
0. 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.
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:
http://www.bdsonline.net/soldering/rstalk.htm
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
http://www.herman.rula.co.za/pdf/resistance_soldering_kit.pdf
or:
http://www.wamrc.org.au/projects/res_solder /
or:
http://www.girr.org/girr/tips/tips1/solderer.pdf
*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?
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
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
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