Very Little Gravitas Indeed*

Discussion in 'Workbenches, including workshop techniques.' started by adrian, 30 January 2017.

  1. David Taylor

    David Taylor Western Thunderer

    I use diluted phosphoric acid to clean up after silver soldering. Works with steel as well as non-ferrous metals but you can't leave the steel in there too long.

    Those coupling rods are excellent, and hand shaped too! Really well done.

    I like the look of that machine you bought too. Jig borers are meant to be very accurate.
    Last edited: 24 September 2017
  2. Arun

    Arun Western Thunderer

    I really wouldn't try that. You are right that water is needed [to create H3O+ ions] but [and it's a very big "but"] conc. sulphuric acid extracts moisture from anything near it and given that you are 70% water, it makes no difference to the nasty unpleasant end result whether you dip your hand in it or just allow the vapour [probably largely sulphur trioxide [SO3]] to caress your exposed skin. {SO3 + H2O = H2SO4}

    Wagonman likes this.
  3. simond

    simond Western Thunderer

    Do as you know you ought-er,
    and add the acid to the water.

    I suspect there was a second couplet bemoaning the fate of those who didn't, but I can't recall...

  4. adrian

    adrian Flying Squad

    Having suggested once again that silver-soldering might be a good solution, I was challenged to "show me".

    So tonight I've done a little example of making some footplate support brackets that would be to quote Tom "troublesome to emboss rivets on once formed". So this is my little silver soldered solution.

    I just used a bit of scrap etch from an old kit, on the base plate I embossed a line of rivets and then on the upright I bent the end at 90 degrees just so that it would stand upright on the base plate. One of the tricks with silver-solder more so than with soft soldering is ensuring the joints are a snug fit. So if you do bend the upright then the corners will swage the metal slightly and it will need dressing with a file to ensure it fits flush with the base plate.

    silver_solder - 16.jpeg

    I then use a little bit of binding wire (previous link now duff so this is similar), which is just soft iron wire, to hold the two components together.

    silver_solder - 14.jpeg

    In the examples previous in this thread I have used little pallions of silver solder but on other recommendations I thought I'd try some silver-solder paste this time.

    silver_solder - 8.jpeg

    I can't remember where I got it from - probably ebay but this from Cooksons would be similar. With silver solder there generally 3 different grades (actually 4 if you count extra-easy)
    1. Easy - "low" temperature melting point
    2. Medium - mid range temperature melting point
    3. Hard - highest melting point.
    As I say some places will offer "extra-easy" which is a lower temperature melting point but stick with the standard 3. Unless you are getting into some serious silver-smithing you can ignore all and just use "easy". I say this for a couple of reasons. First Easy flows nicely so if you're just starting then you stand a better chance of making a good joint with easy than medium or hard. Easy solder will flash into joints in a beautiful way, medium and hard need a bit more work to get a good joint. The second reason is that one of the characteristics of silver soldering is that when you make a silver solder joint then the resultant alloy at the joint has a slightly higher melting point than the original solder. So it is perfectly possible to silver solder a joint with easy and then make another joint without melting the first joint! So my recommendation is stick with easy.

    You may wonder why you contemplate using hard solder at all. I think it's best use in our field is mainly for people building live steam locos. I would consider soldering things like super-heater pipes and boiler fittings with hard solder - then the whole boiler tube plates, throat plates, etc would all be assembled with easy.

    I've never used the paste before so I wasn't sure how much to apply - so the syringe needle was too constrictive to apply it evenly so I removed it and used a wooden toothpick to apply - hence a bit messy.

    silver_solder - 13.jpeg

    Note I have applied the solder to the side opposite to the rivet detail. This is because the intention is to heat the joint from the other side. Just like soft soldering the trick is in the application of the heat - the solder will always flow in the line of least resistance. So if I heat from the other side and warm up the metal then when the solder melts it will flow into the joint nicely as the metal is hot enough.

    Now I moved outside - I usually do my silver-soldering in the shed as I prefer to keep gas canisters and acid baths out of doors. I've moved the stuff outdoors just to get the photos. I do have a little oxy-propane torch for fine jewellery work but for things like this a simple blowtorch and gas can is sufficient. Behind the torch are the soldering plate and bricks I have - again it's one of those things I acquired years ago so I can't remember where I got them from. From cookson something like these are equivalent.

    silver_solder - 6.jpeg

    Even with the solder paste I still thought it prudent to use some flux - this prevents the metal oxidising prior to the solder flowing.

    The different silver solders generally need slightly different fluxes - for Easy solder use "Easy-flo" - this is a powder which you can mix with a little water. Now I have a 250g tub of the stuff which will last me a lifetime plus. So don't buy any - drop me a message and I will post out a little jar of the stuff to you. So I apply this all around the joint.

    silver_solder - 7.jpeg

    Now this is where it get difficult to show the process. I will have a go at making a little video of the actual silver soldering process but basically I start with gently wafting the blow torch over the joint. You need to boil the water out of the flux - do it too quickly and the water boils like mad and spits the flux out left right and centre. So a gentle warming of the piece allows the water to gently boil off - hopefully the photo below shows it gently bubbling away.

    silver_solder - 9.jpeg

    Once it turns dry and crusty then you can start bringing the blow torch closer and applying more heat.

    silver_solder - 2.jpeg

    As you apply more heat then the flux itself turns more "watery" although I'd say more vitreous - like molten glass.

    silver_solder - 1.jpeg

    and then in an instant you get the joy and beauty of silver soldering. All of a sudden you will see a flash of silver run through the joint. It's hard to describe but when it happens you will see the joint form.

    silver_solder - 3.jpeg

    Remove the heat and then drop in an acid bath, I use dilute sulphuric acid which results in a distinct copper colour to the piece. Others use phosphoric acid or boric acid. It's not an essential step as you can remove the flux with mechanical methods - however as mentioned the flux does take on a certain glass like, vitreous quality, so an acid bath does make it a bit easier.

    A set of plastic tweezers used to remove it from the acid bath. This is as it came straight out of the bath.
    silver_solder - 10.jpeg

    As you can see the solder has flashed through the joint nicely - it provides a clean smooth fillet and no cleaning up required.

    silver_solder - 11.jpeg

    So I can now start cutting out the shape required.

    silver_solder - 5.jpeg

    So I've not been that rigorous with marking out and cutting to shape hence some rather wayward rivet detail, I was just going off the details on Tom's workbench so some of it was a little bit of guesswork. - however it's the principle I'm trying to show.

    So final photos - a couple of frame support brackets - silver-soldered so that the rivets can be formed cleanly and being silver soldered means that they can be soft soldered to the loco frames with out fear of the joints melting and falling apart.

    silver_solder - 15.jpeg

    silver_solder - 12.jpeg

    silver_solder - 4.jpeg

    So very few tools required, just give it a go. Practice on a bit of scrap material and have fun. If you get it sorted you can even earn brownie points and make some personalised simple jewellery for your better half!!

    Any queries or clarification required then please post a comment and I'll try to help.
    Last edited: 15 October 2019
  5. Tom Mallard

    Tom Mallard Western Thunderer

    Thanks Adrian for taking the time to inform us all in something you are clearly well practised at.

    The seam of solder has come out very well. The torch used must supply quite uniform heating over the workpiece, but does it anneal the metal to any great degree?

    I'm not sure if it was mentioned, but apart from the relatively higher melting point, silver solder is much stronger than soft soldering in the type of application you've shown, so these assemblies are going to be quite resistant to handling and so-on.

    I see this becoming a much more widely used process once I've got the hang of it.

    Best regards

  6. Peter Cross

    Peter Cross Western Thunderer

    When we used to silver solder clock case parts, we used to quench in cold water which removed most if not all the glazed flux.
    Yes it does anneal the brass. But the quenching and any work soon hardens it off again.
  7. Osgood

    Osgood Western Thunderer

    I must get round to trying this process.
    Years ago I kept the bricks from a big old electric storage heater in the belief they would make ideal firebricks for this purpose - I think they're still kicking around somewhere.
    Can anyone advise if these would indeed be suitable to use?
  8. simond

    simond Western Thunderer

    If they're years old, I'd be wary that they may contain asbestos or something similarly nasty. Probably not an issue if they don't make dust, but...
  9. David Halfpenny

    David Halfpenny Western Thunderer

    I'm very happy with Citric Acid now that it's available again.
  10. Giles

    Giles Western Thunderer

    No - they do a rather different job - they are designed to collect heat and store it, thus depriving the job of the heat you are trying to put in, whereas we want bricks that reflect heat back on to the job instead. The proper ones are quite cheap at a fiver each or even less if you shop around.
  11. David Halfpenny

    David Halfpenny Western Thunderer

    Consider Vermiculate sheets and blocks.
    More expensive than firebricks, but very light, cuttable and formable.
    My whole hearth fits in a square rubber 'bucket'.

    I was sad when someone broke one of my larger sheets, but soon band-sawed the pieces into neat squares and rectangles which are very useful for propping, shielding and reflecting heat.

    From CUP Alloys and others.
    Osgood likes this.
  12. Osgood

    Osgood Western Thunderer

    Ah yes Giles - I should have been able to work that out for myself but failed to spot the obvious.
    I was thinking only of their ability to take localised heat without spalling dangerously - which even then they may not be so good at as conventional furnace refractories as the storage heater thermal loading is much more uniform and gradual.

  13. Susie

    Susie Western Thunderer

    Hi Guys,

    Vermiculate is useful, but I have found that when used as the immediate support when silver soldering the surface tends to decompose quite quickly and so have reverted to firebricks. There is another asbestos alternative which is quite hard and has to be sawn which I have used to form the rest of the hearth but as I got it as off cuts from work I don't know what it is called - sorry!

  14. Chris Veitch

    Chris Veitch Western Thunderer

    I've just picked up on this thread and it's made me happy for several reasons:
    1. I love a peek into someone else's tidy and well-stocked workshop;
    2. Great workmanship - I was so impressed with the technique of silver soldering the riveted strip and then cutting away the waste;
    3. Proves to myself that you can't have too many machine tools (what is that lathe at the RH end of the bench...?);
    4. I found out where the SpaceX landing barge names really came from - I'd always assumed they were obscure Hitchhikers Guide references.
  15. adrian

    adrian Flying Squad

    Many thank for the kind comments - although it isn't quite that tidy at the moment. I tend to work on a project for a bit and the clutter slowly accumulates until I get to a state of not being able to find any thing. So then I get fed up of not being able to find anything and I have to clear the bench and put al the projects into their own boxes.

    Like many things I learn by my mistakes - the riveting is one of them. I have always struggled riveting close to an edge. The process of forming the rivets close to the edge always seem to buckle and distort the edge for me. So I quite often form the rivets in a sheet prior to cutting out as it seems to minimise the distortion.

    The lathe at the RH end of the workbench is another one I acquired many years ago. It's a Coronet Ruby Coronet Diamond, Jewel, Ruby and Tiara lathes in fact the third photo on this page is the very lathe itself, I sent Tony a photo of it many years ago as an example. It's a great little portable lathe and it's got a very nice set of collets with it so I tend to use it for doing some of the smaller precision work with small diameter stock.

    Finally w.r.t. point 4 and the Culture Ships of Iain M. Banks. There is a full list of Culture Ship names on Wikipedia List of spacecraft in the Culture series - Wikipedia

    Unfortunately for WT members Iain Banks is one of my favourite authors so I'm going to indulge myself with one more pub trivia fact. Iain Banks had two different genres of writing, his science fiction stuff he used the name "Iain M. Banks" (Consider Phlebas, Use of Weapons, The Player of Games etc.) and he wrote contemporary stuff with the name "Iain Banks" (Wasp Factory, The Crow Road*, Whit etc.). Now many people love the film of Sandford's finest in Hot Fuzz (Swan!!). In the film there is a running joke with the custody sergeant played by Bill Bailey. He plays a pair of twins in the film - one really scruffy twin is always reading Iain M Banks books, the clean cut well to do twin is always reading the contemporary Iain Banks books. Not a lot of people now that and even fewer give a ****. A clue to the same person - different characters!

    *The Crow Road is one on my favourite books if only for it's opening line which I always remember "It was the day my Grandmother exploded. I sat in the crematorium listening to my Uncle Hamish quietly snoring in harmony to Bach's mass in B minor" - if that doesn't get you hooked nothing will!
    cmax, mickoo and Chris Veitch like this.
  16. Jon Nazareth

    Jon Nazareth Western Thunderer

    These Titanium strips can be filed and then bent up to whatever sort of clamp shape that you want. The joy with these is that they don't move/expand with heating up for silver soldering. They are used in the jewellery, or whatever use you can think of, trade and very good they are too. I bent up the one in the picture and it works a treat and, the silver solder will not stick to it...even better.


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  17. simond

    simond Western Thunderer

    Thanks Jon,

    useful info, I will investigate and maybe invest

  18. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    This may be a numpty question but are silver solder fluxes acidic in the same way as soft solder fluxes?

    And another.... after removing the item from the acid bath would you not rinse it in an alkaline solution to neutralise any remaining acid?
  19. mickoo

    mickoo Western Thunderer

    Note to the Admin, I think we need a new tag....'Rabbit hole' :D :thumbs:
    Rob R and adrian like this.