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Flux for HMP soft solder?

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Graham V11/11/2009 15:20:20
4 forum posts
Hello all,
 
Can anyone recommend a flux suitable for use with HMP (about 310 deg. C) soft solder?
 
Having been a Plumber and heating engineer for over 40 years, I have no trouble at all with the lower melting point soft solders or indeed silver soldering and "spelter" brazing as I have suitable fluxes.
 
I have however yet to find a flux which actually works with HMP soft solder.  Fluxite and Carrs Green Label have been suggested to me and tried but I found these to become exhausted before the required temperature was reached,  Silver solder fluxes, on the other hand have a too high working range.
 
Many thanks,
 
Graham
 
 
Geoff Theasby11/11/2009 16:08:32
615 forum posts
21 photos
I have had the same problem.
I bought Fry's Powerflow Flux at the local ironmongers, specifying it was for brass.
It didn't work.
As it happens, I was building an engine for use on compressed air only, so I soft-soldered it with electronic cored 60/40 solder, which worked beautifully.
Chronos Engineering Supplies at www.chronos.ltd.uk list various solders and fluxes. (Usual disclaimer)   I shall go to them next time.
 
Regards
Geoff
Graham V11/11/2009 17:06:50
4 forum posts
Thanks for that Geoff.  I am glad that I am not the only one having this problem.
 
Yes, I have tried Powerflow which as you say doesn't work.
 
In fact it was Chronos who recommended Fluxite and Carrs Green label which also didn't work.  I asked them after unsuccessfully trying several of the fluxes that I use for plumbing work.  Hence the posting as there must be something suitable around.  After all HMP solder is readily available and mine does have flux cores maning it usable in fery small blobs!
 
Regards,
Graham
 
JasonB11/11/2009 17:20:05
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25215 forum posts
3105 photos
1 articles
Not tried it but Reeves do a flux for Comsol (305deg) called "Thesco SC5" could be worth a try.
 
And Cup Alloys also do a flux for their 296deg solder
 
Jason

Edited By JasonB on 11/11/2009 17:22:06

John Baguley11/11/2009 20:07:42
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517 forum posts
57 photos
The 'traditional' flux is Bakers Fluid but you have to keep slopping it on all the time as it quickly evaporates. Carrs Black Label works quite well but with the same evaporation problem. The difficulty is finding a suitable brush to apply it with that will stand the temperature without going all black and horrible! Maybe something like an eye dropper would be a better way of applying it?
 
John
mgj11/11/2009 22:53:33
1017 forum posts
14 photos
I 've used Comsol with Bakers fluid and it worked perfectly. Coated both surfaces, and then dipped the end of the Comsol in it. It was, on steel, no different form any other soldering - except a bit warmer.
 
As I understand it, Bakers Fluid is supposed to evaporate. It is, like any other flux, the molten solids which do the cleaning. The liquid is just a medium for getting the solids (zinc chloride?) to the right place. May be wrong.
Graham V13/11/2009 12:03:46
4 forum posts
Thank you all for the above replies.
 
I have not tried Bakers fluid but I suspect that John is right.
 
JasonB's reply looked promising but Reeves told me that they have dropped their flux for Camsol, presumably Thessco SC5, and I have been unable to find any information of stockists.  Also Cup Alloys only do a general purpose soft solder flux, which may be OK, but can't send it by mail - "collect only from exhibitions" is stated and there are no exhibitions in East Sussex attended by them that I can find.
 
So, can anyone tell me more about Thessco SC5 availability, please?
 
Thanks to all,
Graham
mark bosworth02/12/2010 21:17:32
1 forum posts
hi there i work in the sign industry making letters out of steel brass etc for soldering purposes we use bakers fluid to clean copper soldering irons (tinning) and thesco sc5 as a flux both work really well but if left out bakers will evaporate and sc5 turns to from a paste to a watery substance still works but can be messy both these applications can be used for either hi or lo temp solder  many regards mark cromwells stock it also firth supplies leeds but can be pricey many regards mark
 
Richard Parsons03/12/2010 09:00:28
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645 forum posts
33 photos
 

Bakers soldering fluid.  Get some COTTON cloth (it must be cotton - not a union of cotton and manmade fibre) make up a pad and hold it in a twist of iron wire (not a plated type). Use it to apply the baker's fluid. I learned this trick from a panel beater who used to fill the soft curves on real motor cars at Pressed Steel.

Cotton has an ignition point of about 407°C. this rises when the pad is soaked in a water based fluid like Bakers

Gordon W03/12/2010 09:35:28
2011 forum posts
Another way to apply Bakers fluid, for small jobs is a bit of tube, with finger over end, eye dropper really.I'm using Bakers for all soft soldering now I've managed to buy some. ( except electrical)

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