Low temp soldering.

[stewartingram]

I've been trying to find advice on what temperature to set my iron to when using various low-melt solders. I have a number of articles in books and magazines but none seem to mention this. Most seem to say go in quickly with a lot of heat and withdraw quickly.

So if I have a whitemetal loco kit, and want to build in stages with different solders, what is the best way? I envisage normal temp could be used (but carfully) with large parts, but would prefer to drop the temp so as not to melt the castings irretrievably. And the smaller parts, go for a lower temp & solder.

As for a etched kit, not much chance of melting the brass, but what if I'm adding whitemetal bits which are small?

So does anyone have a guide to temperatures for each type of solder?

 

Stewart

[Quarryscapes]

With 70 degree stuff I found Iron temp of about 170-190 was about right but it was sloooooow going as the whitemetal castings soak up so much heat. 

[Nearholmer]

My method is crude but effective.

 

Temperature control is a lighting dimmer, with an incandescent lamp across the output to give a very rough indication of output voltage.

 

I take a scrap of the white natal in question, and a couple of solders, then fiddle with the setting until the solder flows nicely, checking that this temperature doesn't cause the iron to melt a small scrap of metal - then mark setting on knob with an indelible pen.

 

I've made many things using this system, without difficulty. My soldering station cost about a fiver to make, thirty years ago.

 

Kevin

[Orange Cat]

There's more risk of melting small parts than large ones. I agree with the books and magazines. A good hot iron to make the joint quickly before the heat flows into the parts and melts them. Get everything set up, clean the parts, plenty of flux, the parts positioned so they won't move and then quickly run the solder into the joint. One tip I would give is if the joint isn't successful right away, i.e the parts aren't correctly positioned or the solder hasn't run into the joint, then don't keep the iron in place trying to correct it. Cool everything down, clean the parts off and try again. Residual heat in the parts or applying heat for too long are the quickest ways to melt parts. Good technique is far more important than the temperature of the iron.  

Soldering whitemetal parts to brass, tin the brass with normal solder first then use low melt to make the join.

[JaymzHatstand]

I've got a Weller temperature control iron, the low temp version and have found that for whitemetal soldering thus far that having the control dial set to number 4,out of 6 and using 70 degree solder has been absolutely fine. I've not done anything larger than a DJH loco in OO and it's coped well with that.

 

I'm not sure what temperature that is in real terms, but hopefully it'll be of some help!

 

As for adding castings to brass, if you tin the area of the brass with regular solder first it gives the low melt something to key to which is often better than the bare brass.

 

Cheers

 

J

[Nearholmer]

PS: I use the largest iron that will fit the job, because it acts as a heat reservoir. Lack of heat reserve leads to trouble, with temperature getting dragged down below the "nice flow" point.

[Mr Grumpy]

The white metal MUST be scrupulously clean at the mating faces. If not the solder will probably just turn to balls:-)

When I built my DJH 47 in 7mm scale, I believe I had the iron set to around 140. As my cofidence grew, I just used ordinary 145 solder, with the iron around 350. But the castings were big :-)

[stewartingram]

Some useful advice, but not quite what I asked. I have a Maplins 48W temperature controlled iron. I have a range of solders of different temperatures. If I was to use (say) the 145 solder, what temperature would I set the iron to? Again, if I swopped to another solder (say) 70 degrees, what would I change the iron to for that? I could go out to the man cave and list all the solders I have but it is cold dark and damp outside....

Not much use trying to solder a whitemetal buffer to etched brass with a (too) hot iron and trying to be quick about it?

 

Stewart

[Mr Grumpy]

Some useful advice, but not quite what I asked. I have a Maplins 48W temperature controlled iron. I have a range of solders of different temperatures. If I was to use (say) the 145 solder, what temperature would I set the iron to? Again, if I swopped to another solder (say) 70 degrees, what would I change the iron to for that? I could go out to the man cave and list all the solders I have but it is cold dark and damp outside....

Not much use trying to solder a whitemetal buffer to etched brass with a (too) hot iron and trying to be quick about it?

 

Stewart

Hi Stewart,

As my post above,

I set the iron to 140 for 70 degree solder and around 350 for 145. I didn't have any problems regarding melting anything, but I did regularly check on similar scrap pewter/white metal first. My iron is an Antex 50w TCS.

[John Tomlinson]

I've recently bought exactly the same piece of kit as Stewart, seems to work very well but I'll be interested to know the answer to the question he's raised. For £25 it seems amazingly good value, and I'm looking forward to trying it on some beefy 7mm work.

 

Previously I used the same system as Nearholmer in #3, which also worked well, however the the 40W Weller iron I have always seems to blacken very quickly unless you keep turning it down or indeed off, which is a real pain.

 

John.

[stewartingram]

OK just for clarification I've just checked my solder stocks. I have the following:

 

60/40 cored electrical solder of various gauges (normal lead/tin)

Lead free electrical solder (rarely use this as I don't like it as a substitute)

188 degrees

145 degrees

70 degrees

 

My normal iron is a temp controlled Weller 48W (magnetic bit to change temp) as I work in electronics.

The other iron is a temp controlled Maplin 48W which is almost unused, I got this on a very special offer price specifically for modelling work. It can be preset to a dial-up temp.

 

So already I have had figures quoted for 140 degrees (70) and 350 (145). This is approx. twice the tem of the solder, I seem to recall hearing this ratio before, possibly on a training course many years ago?

 

Stewart

[Nile]

I've got a Weller temperature control iron, the low temp version and have found that for whitemetal soldering thus far that having the control dial set to number 4,out of 6 and using 70 degree solder has been absolutely fine. I've not done anything larger than a DJH loco in OO and it's coped well with that.

 

I'm not sure what temperature that is in real terms, but hopefully it'll be of some help!

 

As for adding castings to brass, if you tin the area of the brass with regular solder first it gives the low melt something to key to which is often better than the bare brass.

 

Cheers

 

J

 

4 on the dial probably means 400F, about 200C, which seems about right. Weller stuff tends to be in Fahrenheit.

[Nearholmer]

JT

 

I've given up worrying about weller tips going black - it seems unavoidable.

 

They can be got bright again by cleaning on a damp sponge, or using abrasive paste, but when they get too gnarled, I file them back to shape, then re-tin, and the cycle starts again.

 

K

[Crantock]

I did have a look through the Carrs Soldering Handbook (decode = catalogue). That doesn't have a range of temps at all for solders.

 

However, it does say "most white metal casters use alloys that melt between 225 and 243 degrees c". The "most" is important but the point is that for whitemetal a temperature below that with a good margin should be fine. I use 212c on a 70 degree solder. Let's say that's the maximum safest.

 

For adding to an etched kit the point is to use the highest temp solder first 188. Then 145 for detailing then 70 for adding the whitemetal ( but bearing in mind you may need to tin the receiving surface first). You could probably go as hot as you like for 188, it's just about not melting what you have done - hence in fast. The 145 is prob the same temperature as the risk is melting other 145.

 

I would say that the best move I made was not trying to use maplins electric solder. The lower temp of 188 is so much better.

 

Books do suggest using different tips for diff temps. I assume x contamination.

[Quarryscapes]

Books do suggest using different tips for diff temps. I assume x contamination.

 

Yes, whatever you use for the 70 degree stuff you must only use for 70 degree again in the future, I can't remember the temperature but getting it too hot releases cadmium vapour which ain't nice stuff I'm told.

 

I don't think it was true of any other solder, but you'd better check with someone more qualified in such matters. 

[Sandy Harper]

I have found that I only ever need three types of solder.  60/40 tin/lead for general brass or N/S construction using Copalux flux. Carrs 100deg stick solder for white metal which does not need a tinning of another solder on the brass. Carrs 188 degree for filling!!

 

Steel needs Bakers Flux as the Copalux won't cope with it

 

188 and 60/40 solders I use a temp of 450 degrees and the 100 degree solder about 320 degrees when fixing w/m to brass and 280 degrees w/m to w/m but always use a heatsink around the w/m castings to prevent meltdown!

 

Cleanliness is next to godliness. Everything! that includes your metal, iron, solder and flux. Old solder will get a surface contamination on it after a while under certain conditions. Get rid of it and buy new. The number of times I have heard modellers say that they can't solder and then find they are using a huge roll of solder that their father used!

 

Sandy

[bertiedog]

I can't see it mentioned in the sage advice here about low melt, but there is an important point, the iron tip must be tinned with 60/40 containing lead before any work with the low melt, and every so often the iron should be heated up and re-tinned. The high bismuth content of woods alloy etc., do not alloy with most soldering iron tips, so the 60/40 tinning is vital.

Summarising the use of low melt it does not need for the iron to be set as low, twice is best, but full power may be needed for large whitemetal chunks being soldered, as the heat is soaked up. With tiny fittings, then set the iron to just above the low melt temperature, and you will not melt the castings.

 

Stephen