Soldering - irons - solder - fluxes - techniques

[Jol Wilkinson]

At last iv`e made a start on my DJH 7mm Fairburn tank,I bought one of these from Maplin & it`s just the job.

 

http://www.maplin.co.uk/p/60w-professional-lcd-solder-station-with-esd-protection-a55kj

 

 for soldering in the axle bushes,I use 145 deg.solder with the temp set to 450 as the frames are quite thick.

Best of all,it`s still on offer at £39.99.

 

   Ray.

Looks good but I've always had reservations about continued availability of spare bits and elements for Maplins TCUs. I'd be inclined to get a spare element and several bits while they list them.

 

However, the spare tips listed have a fine point, probably for electronics work. They tend to restrict the heat flow owing to the small cross section at the end of the tip, which is probably why you are having to turn up the temperature  to 450. A chisel type bit with a larger contact surface area is better for modelling work. Antex and others supply a variety of tips better suited to soldering models.

[sagaguy]

Apparently,Hakko bits fit these irons & are easily & cheaply available on ebay.Iv`e just ordered a set & will let you know.

 

 

                 Ray.

[Graham Hughes]

Many on here mention temperature controlled soldering irons and different solder melting points.

Is there a rule of thumb/ hard and fast rule relating soldering iron to solder temps?

I only ask, not to sound stupid, but because in my head if the solder melts at 145 deg my iron will need to hotter than that to transfer 145 deg to the part in question and then to the solder, but how much hotter?

As hot as it gets. It is not just a case of how much higher the temperature needs to be. The important thing is the heat flow. This depends on the temperature differential and the thermal conductivity of the material. As you put heat onto the joint it will dissipate in the rest of the model according to how well the material conducts heat. Brass is a particularly good conductor of heat which is why I much prefer nickel silver when scratch-building. You therefore need to be able to put heat into the joint more quickly than it is being conducted away from it. Ideally you need to do this a lot more quickly, especially on a part constructed model as you want to solder the joint you are working on before the rest of the model heats up to the point where the previous joints melt. So you need a tip that is big enough to transfer the required heat and an iron of sufficient power that it can keep up with the heat being drained from it. If you are soldering at 145^oC you want a set up that will get the joint to that temperature as quickly as possible, not one that will heat the whole model to that temperature over a longer period. The more heat you can put in, as quickly as possible, the faster you can get the joint finished and the heat source removed before anything else starts to come undone. 

 

 It is hard to envisage any conventional soldering iron getting too hot and very easy to not have it hot enough, especially with the temperature-controlled ones. Being able to control the tip temperature might be important if you are soldering temperature sensitive electronic components, (which is what these "soldering stations" were designed for) and maybe white metal components if you are not confident in your soldering skills, but there's no real point for soldering sheet metal in model building work. Soldering is really a very simple process. There is no need to over-think it. Clean parts, a good hot iron with a clean tinned tip, a suitable good quality solder, plenty of flux and plenty of practice are the keys to being able to solder well.

[brossard]

Tony Wright, in his Right Track 1 DVD on loco kit building says that a rule of thumb for temp controlled irons is to have the tip temp set to twice the solder melting point.  I think if you experience refreezing (when the bit sticks to the work), temp isn't high enough.  I tend to have mine set to 340C.

 

No doubt Graham is right about the need for a soldering station, however, I do like mine.  I like the idea of knowing what my tip temp is.

 

John

[Jeff Smith]

It's really the solder that is largely responsible for transferring the heat into the joint so you also need enough solder, but not too much.....the flux allows the hot solder to flow over the material surface and thus transfer the heat, so the solder needs to be hot enough to be able to loose some heat and still stay liquid enough for capillary action into the joint.

[Graham Hughes]

It's really the solder that is largely responsible for transferring the heat into the joint

Not if you are doing it right, it isn't. The soldering iron heats the joint, then you apply the solder. If you rely on the solder to heat the joint you risk "dry" joints. 

[sagaguy]

Not if you are doing it right, it isn't. The soldering iron heats the joint, then you apply the solder. If you rely on the solder to heat the joint you risk "dry" joints. 

 

 

After years of silver & soft soldering on large scale steam locos,i normally flux the joint,cut a small piece of solder,lay it on the joint & apply a hot iron to it.If youv`e cleaned & fluxed properly,the solder should flash into the joint but you do need the iron hot enough,430-450 deg.for thick brass such as mainframes.

 

Silver soldering of course was done with a Propane torch

 

Ray.

[raymw]

(Ignore the following if you are of a sensitive disposition)

 

Nobody seems to be using a solder gun ( like http://en.wikipedia.org/wiki/Soldering_gun ) . You could, if you were brave enough, most likely rip one apart and turn it into a rsu. I made an rsu from an 85A 12V toroidal transformer - that's about 1KW!. At 12V, I can draw out a nice arc. I wanted to regulate the power by pulsing it on an off, maybe ten times a second (pwm) but didn't have a powerful enough mosfet to do that on the secondary side, so I used an electronic relay on the primary side. Because of the very high inrush current in toroidal transformers, this causes significant flickering in the house lighting circuits, and . I bought a variac, to reduce the primary current, and can regulate the output from white heat down to barely warm. I use welder's carbon gouging rods (about 3/8 inch diameter), sharpened with an ordinary pencil sharpener as the electrode, I've had no success with carbide rods. The advantage of an rsu, is that you can often position the items with the end of the carbon rod, use the rod to press the sheets together, apply current momentarily to melt the solder, then hold the electrode in position until the solder sets.  I have found that the theory, wrt the heat being generated at the surface resistance between the metal and solder is a fallacy - the heat is at the tip of the carbon rod, (or the whole rod, on high current  ) For flux, I normally use phosphoric acid, full strength from agricultural suppliers (milk stone remover- about £15 per gallon) which I also use it to clean stainless steel welds)

 

Best wishes,

 

Ray

[Jeff Smith]

Not if you are doing it right, it isn't. The soldering iron heats the joint, then you apply the solder. If you rely on the solder to heat the joint you risk "dry" joints. 

Well, it's actually a combination.  The iron in contact with the metal is an edge or point contact which is not the most efficient heat transfer method although if your iron is 'really' hot it will seem efficient.  The flowing solder wetting the surfaces of both the iron and the joint is a very efficient heat transfer medium because of the area.  However, as you say, if the solder is not hot enough you do risk creating a dry joint if the solder does not heat the joint sufficiently.  I am in the aerospace electronics business and even with very well regulated solder baths for soldering electronic components to multi-layer PCBs occasional dry joints are created....and the only way heat gets to the joints with a solder bath is via the solder.  Temperature has to be controlled quite tightly to prevent damage to the components.

[Jeff Smith]

Here's another question - how widespread is the use of lead-free solder in the hobby world. I believe industry is having to move to lead-free but Radio Shack in the US (Tandy? in the UK) still has a mixture of leaded and lead-free.

[sp1]

Here's another question - how widespread is the use of lead-free solder in the hobby world. I believe industry is having to move to lead-free but Radio Shack in the US (Tandy? in the UK) still has a mixture of leaded and lead-free.

Not sure about the answer to your question, but I have tried it and it is the work of the devil!

I think it very telling that lead solder is still approved for medical and military use (if I have read correctly).

[raymw]

I had thought Tandy had closed down in UK, but it seems they now have a mail order system - not one I'd use. Solder with lead in it is readily available from the usual electronic suppliers. I tried to quickly find the recent legislation, but failed. However it has to be lead free solder in a range of new electronic equipment, based on this - http://www.psma.com/ul_files/forums/leadfree/aim_lead_free_guide.pdf (page 2). If you are a manufacturer of soldered models, you should be OK, but not if classified as 'toys'. Plenty of arguments on rmweb, and other places against lead free solder. Personally, I've not found much difference in the small amount of pcb work that I do, nor in the even less brass etch assembly.

[runs as required]

(Argos 30.11.2014) Having conducted a quick search of the site  I was surprise to discover there is no general thread for capturing help and advice with soldering.

Doubly surprised given this is such an important skill for constructing most of the kits we attempt.

 

At last iv`e made a start on my DJH 7mm Fairburn tank,I bought one of these from Maplin & it`s just the job.

 

http://www.maplin.co.uk/p/60w-professional-lcd-solder-station-with-esd-protection-a55kj

 

 for soldering in the axle bushes,I use 145 deg.solder with the temp set to 450 as the frames are quite thick.

Best of all,it`s still on offer at £39.99.

 

   Ray.

Yes I'm a contented user of one of these now  too - a couple of weeks after posting on your thread about my travails trying to join heavy chunks of white metal.

 

I think I am now up to speed, using this iron fitted with the chunky wedge bit, in coping with 'heatsink' issues while soldering white metal (in quick with a hot heavy iron on really clean castings with 145 deg. solder on the hidden bits of heavy castings for strong bonding, then gap fill in with slivers of 70 deg using liquid O gauge flux.)

 

I've never had problems with etched brass and track soldering  - assuming you have rehearsed beforehand just how you are to provide the 'extra pair of hands' to position the pieces (mentioned above).

 

To answer Argos's opening question, allow me pass on some links I found:

 

http://www.7mmlocomotives.co.uk/index.php?option=com_content&task=view&id=37&Itemid=45

 

http://www.rmweb.co.uk/community/index.php?/topic/39669-soldering-white-metal/

 

http://www.rmweb.co.uk/community/index.php?/topic/64699-whitemetal-soldering-advice/

 

http://www.rmweb.co.uk/community/index.php?/topic/52275-white-metal-soldering/

 

http://www.rmweb.co.uk/community/index.php?/topic/54928-soldering-iron-for-whitemetal/

 

http://www.rmweb.co.uk/community/index.php?/blog/1519/entry-15068-74xx-first-attempt-at-a-whitemetal-kit/

 

Happy Hunting

 

dhig

 

 

[Jol Wilkinson]

(Ignore the following if you are of a sensitive disposition)

 

Nobody seems to be using a solder gun ( like http://en.wikipedia.org/wiki/Soldering_gun ) . You could, if you were brave enough, most likely rip one apart and turn it into a rsu. I made an rsu from an 85A 12V toroidal transformer - that's about 1KW!. At 12V, I can draw out a nice arc. I wanted to regulate the power by pulsing it on an off, maybe ten times a second (pwm) but didn't have a powerful enough mosfet to do that on the secondary side, so I used an electronic relay on the primary side. Because of the very high inrush current in toroidal transformers, this causes significant flickering in the house lighting circuits, and . I bought a variac, to reduce the primary current, and can regulate the output from white heat down to barely warm. I use welder's carbon gouging rods (about 3/8 inch diameter), sharpened with an ordinary pencil sharpener as the electrode, I've had no success with carbide rods. The advantage of an rsu, is that you can often position the items with the end of the carbon rod, use the rod to press the sheets together, apply current momentarily to melt the solder, then hold the electrode in position until the solder sets.  I have found that the theory, wrt the heat being generated at the surface resistance between the metal and solder is a fallacy - the heat is at the tip of the carbon rod, (or the whole rod, on high current  ) For flux, I normally use phosphoric acid, full strength from agricultural suppliers (milk stone remover- about £15 per gallon) which I also use it to clean stainless steel welds)

 

Best wishes,

 

Ray

Ray,

 

you may have found it a fallacy but I haven't. If the tip of the carbon probe is glowing red hot, then - with 4mm material thickness's at least - you get burn marks on the surface of the metal - or worse!

 

One gallon of acid, cut back to 12%, will produce eight gallons. More than many of us might need in a lifetime and something of a storage problem.

 

Jol

[sp1]

I think soldering, up to a point, is what works for you.

Years ago I build radios/ amplifiers etc (just for fun) - I had a soldering iron from Tandys - lasted for years! Only ever used cored solder (and it worked) : but this was for electrical work: mainly soldering to PCBs - never had a problem with the 'clag' I now get on the bits (Antex).

The only problem I had was a 'dent' formed in the bit from wear - my father filed the bit flat again and it carried on for years!

 

Have materiasl changed (apart from lead free solder, which I don't use) - every bit I have for for Antex irons quickly gets covered in black 'clag' - and I do clean everthying.

The only thing different is the flux used (never used to use it for electrical work - cored solder) : the only things I use different nowadays is flux (Carrs Red) and the cleaning sponge : never used to use either, and never had a problem (I can see the need for flux, as not using cored solder - am I using wrong flux (never had this problem years ago........)

[brossard]

Quite some time ago now, I bought a cheap iron from Radio Shack (I think it cost $10).  I got one use out of it before the bit "clagged" up.  Shortly after, I bought a more expensive Weller iron (maybe $60) and this lasted for years (all it needs is a new bit) - all I ever did was give it a wipe with damp sponge.  I have no experience with Antex, just saying.  Currently using a Weller soldering station, bit is fine after more than a years' use.

 

I agree with your first line though.

 

For me, I use Carr's green for everything.  The label colour is about the concentration of the Phosphoric Acid I suspect.

 

John

[Graham Hughes]

I think soldering, up to a point, is what works for you.

I think that is true but it helps if you become competent with the "right" way to do it so you know when it's right to do it "wrong".  There seems to be a lot of misconceptions around soldering too which doesn't help if you are trying to work out how to start. 

 

As to the Antex tips I found the best option was one of these http://www.soldering-shop.co.uk/catalog/tip-tinner-cleaner-p-95.html?zenid=e075ec7182ba51f079e211e06b145d74&gclid=CIu30dmzrcICFdQZtAod7DIAaA  An occasional rub on that keeps the tip nice and clean with a good tinned surface. I had Weller irons before I went to the Antex ones and I thought they were at least as bad for losing the tip. 

[Down_Under]

I have a question about fluxes.

 

Basically what's the major difference between the products? Carrs Red, Yellow and green. Phosphoric Acid? Then there would appear to be some synthetic fluxes.

 

I have heard of people diluting rust stopper compounds etc.

 

My major reason for asking is living in Australia, there seems to be a limit to what kind of products I can get locally. Carrs fluxes are not one of them readily where I live.

 

J

[runs as required]

I have a question about fluxes.

My major reason for asking is living in Australia, there seems to be a limit to what kind of products I can get locally. Carrs fluxes are not one of them readily where I live.

J

Strange an Aussie should ask this.

I've found one of the very best sources for this kind of info (and also products) is Richard Johnson of DCC Concepts.

[Argos]

Thanks Dhig,

 

For some reason I cannot paste links into the posts at the moment, I was going to try again and update the first posts with these links this weekend.

 

Instead I'll just put a pointer into your post.

 

Regards

 

Angus

[sagaguy]

Apparently,Hakko bits fit these irons & are easily & cheaply available on ebay.Iv`e just ordered a set & will let you know.

 

 

                 Ray.

Got my Hakko bits today & they do fit Maplins 60w soldering station.

 

             http://www.ebay.co.uk/itm/10-pcs-Uk-Common-Solder-Soldering-Iron-Tip-for-Hakko-Station-900M-933-/221622878103?pt=UK_Home_Garden_PowerTools_SM&hash=item3399c0bf97

 

Mine came from Leicester, very quickly but i notice that they now come from China,a bit longer delivery.

 

 

 

        Ray.

[57xx]

Have materials changed (apart from lead free solder, which I don't use) - every bit I have for for Antex irons quickly gets covered in black 'clag' - and I do clean everthying.

 

 

I think they changed a while back. I had an Antex soldering iron I got while doing my electronics degree at Polytechnic 28 years ago. The tip on it lasted until about 5 years ago when I accidental dropped the soldering iron and it bent the tip. All of the replacement tips I got suffer from the black gunk on them that prevents being able to tin the tip properly. I use exactly the same routine as I had done on the old tip which never suffered from that black stuff, even using the same multi-core electrical solder.

[johnarcher]

I have a question about fluxes.

 

Basically what's the major difference between the products? Carrs Red, Yellow and green. Phosphoric Acid? Then there would appear to be some synthetic fluxes.

 

I have heard of people diluting rust stopper compounds etc.

 

My major reason for asking is living in Australia, there seems to be a limit to what kind of products I can get locally. Carrs fluxes are not one of them readily where I live.

 

J

Could I please ask much the same question about alternatives, i am having trouble finding phosphoric acid flux here in France, and you can't, of course, get it posted from the UK any more.

[Jeff Smith]

Try looking in regular hobby or craft shops for stained glass supplies - as mentioned above I found some in the US which is actually 10% glutamic acid hydrochloride. It is advertised as safety flux and seems to work. Cheap too, 8oz for $3.50.

[raymw]

If you have an 'Amazon' in your country, you can most likely get phosphoric acid in the quantity you want. There are plenty of other sources, too, but it may not be in pretty little over-priced bottles labelled 'special red label flux formulated for soldering brass model railway etches' /whatever, but it will be cheaper, and do the job, and many others, just as well. Your local agricultural supplier will sell it, at about £15.00 per gallon (used for removing the calcium deposits in milking equipment), food manufacturing suppliers will sell it (it's cheaper than citric acid), your builders' merchants will sell it for cleaning brickwork, your car spares shop will sell it as rust killer, your hardware store will sell it as kettle de-scaler, etc. Just look at the label it should mention the active ingredients.