Silver soldering small components

Hi All
As I am making progress on my 2” scale Clayton steam wagon clutch mechanism I thought I would share how I silver solder small components.
The biggest issue I find is holding the components together during the soldering process so they don’t move. Over the years I have come up with several different solutions to this problem. The issue with silver soldering is a gap of about 0.05mm - 0.1mm (0.002” - 0.004”) is needed to allow the solder to capillary into and through the joint. So clapping tight together is a no no as the solder will only sit around the edge and not penetrate the joint.
So when tight fitting components are needed to be soldered like the examples you below these need to be addressed.

The first example is a key in a keyway. As the key is tight fit the the keyway the underside of the key is simply gouged in this case with a junior hacksaw so the solder can flow into and under the tight joint. To stop solder attaching itself to areas I don’t want it to be I use a paint pen to cover the areas to be protected as the solder will only capillary to clean surfaces.

Flux is a key component to obtaining a good joint. I mix the powder with clean water until it is slightly runnier than toothpaste. Adding a little water at a time.

Attachment 34796

Attachment 34788 Attachment 34789
Junior Hacksaw groove.

Attachment 34790
surfaces painted with pen to protect from unwanted solder.

Attachment 34791
key in place and a sacrificial bar also painted to hold the key in place.

Attachment 34792
Ready for soldering flux has been added to joint. (note the small price of solder cut from a stick)

Attachment 34793 Attachment 34794
The solder has penetrated through the joint.

Attachment 34795
Sacrificial bar removed.

To clean in this case I use my shot blast cabinet but if it was a pressure fitting it would go into a acid bath. (Water and Sulphuric acid: Safety note add acid to water)

Second example:
I have made a bell crank and held the pieces together with screw. Remembering to leave a gap. The bushes are made slightly wider than the mating plate so when clamped leave a small gap. The bushes are a slide fit. The screws holding the pieces together are again painted so any chance of solder bonding these in place is eliminated.

Attachment 34797
components tone soldered

Attachment 34798 Attachment 34799
Both clamping bolts and components painted.

Attachment 34800 Attachment 34801
fluxed up and solder in place. No such thing as to much flux!

Attachment 34802
soldered am screws removed.

Attachment 34803 Attachment 34804
completed bell crank.

Attachment 34805
Dog clutch and bell crank.

Hope this will be of interest and thank you for viewing
The Home Engineer

Superb workmanship, that bell crank looks like a casting which I suppose is the objective. Thanks for the hints on silver soldering.
I do a lot of stainless parts for my motorcycles, do you have any tips on fluxes and rod for that material?.

Hi Olderdan
I use Johnson Matthey easy flo flux stainless steel (SS) grade for everything (purple tin) steel, brass, copper, stainless and so on. It has a higher temperature tolerance so gives you longer to solder without everything going black as the flux burns off. Rather than the standard easy flow (green tin) This SS grade flux can be used with all solder in their silver solder range. On stainless I normally use easy flow silver solder which is the lower end of the temperature range for silver soldering 650-680 degrees. If you go to the higher end the flux is on its limits and can burn off. Everything has to be spotlessly clean to get a good joint. You can never have to much flux. I Hope this helps please let me know if you need any more information.

Attachment 34827
The Home Engineer

Thanks home engineer that info will be useful to me, I noticed your dyslexia comment. I to am so afflicted, apparently 1 in 10 adults have the condition to some degree so maybe 1700 members on HMT. I am sure that will be corrected. This was never noticed in my school years so I was just considered a bit slow but apparently it is not an indication of basic intelligence. Aniway thinks agaan.

You can also buy small premixed tubes of powdered silver solder and flux in various grades. Just carefully "grease" the joining surfaces with this, clamp if necessary, wipe off excess and heat up with a torch. It is very clean to use, and a small tube is often cheaper than a stick of silver solder. If having trouble with any type of silver soldering it is often a good idea to silver-tin the components first. Once lightly fluxed, assembled and heated, they stick together like magic.

Excellent craftmanship!

I have three questions on your technique:
Q1) How do you preheat the metal parts? Would a butane torch work in this case?
Q2) How do you measure the correct temperature range for soldering? Would Tempil Sticks (temperature-measuring crayons) work for this application?, or a thermocouple?, or a temperature gun?
Q3) At what point does brazing become necessary (in lieu of silver soldering)? Presumably the stresses on your parts during operation aren't high enough to cause the silver solder joints to fail?

Gary Kingsep (kngtek)

Nice work, and a lot of patience to make them!!!
Do you have tested silver(I have copper soldering too) soldering with sheet solder, since I use that they are a lot of difficulties which disappeared, especially for soldering hard metal on tools or replacing hard metal teeth on saw blades.

Quote:

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Originally Posted by kngtek

Excellent craftmanship!

I have three questions on your technique:
Q1) How do you preheat the metal parts? Would a butane torch work in this case?
Q2) How do you measure the correct temperature range for soldering? Would Tempil Sticks (temperature-measuring crayons) work for this application?, or a thermocouple?, or a temperature gun?
Q3) At what point does brazing become necessary (in lieu of silver soldering)? Presumably the stresses on your parts during operation aren't high enough to cause the silver solder joints to fail?

Gary Kingsep (kngtek)

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Hi Gary

Thank you for the comment.

I use a Mapp gas and Bernzomatic torch https://www.screwfix.com/p/bernzomat...ng-torch/71976 for small fabrications which quickly gets most smaller materials up to temperature. On the bigger fabrications like copper boilers I use a Sievert propane gas torch off a large propane bottle. The reason for this you have the option to change the torch burner size. On my Sweetpea Loco boiler I had two large Sievert torches to maintain the heat need. Practical Engineering Some people use the propane for main heat and a Oxy/Propane for localised heat.

To measure the temperature is a combination of things. The first being experience (please don't think I am blowing my own trumpet, believe me I had a lot of items end up in the scrap bin when I first started silver soldering) But the best advise I could give is the flux.

The flux goes through four changes as you heat it.

1st: when heating the water is evaporated off so the flux bubbles up white.

2nd Once the bubbling stops it settles down to a smoother white almost like back to powder.

3rd: As the temperature increases the flux changes state again and looks like glass (at this point very close to the soldering temperature 600 degrees)

4th: the flux then goes into a almost water/clear state and this is when the temperature has been reached to apply the rod (650/700 degrees).

Another couple of tips for anyone starting out silver soldering is:

The job has to be spotlessly clean to allow the solder to flow.
You can never apply to much flux. But you can apply to much solder which can be expensive, unsightly and difficult to clean up.
Do not put the solder stick to close to the flame as the end will melt and drop off. Remember it is the heat from the job that melts the solder NOT the flame. So you must get the heat correct in the job for the solder to flow.
Try and heat from one side of the job and apply the solder opposite as the solders capillary action will be drawn to the heat source and the solder will flow nicely into the joint.

Brazing is another level up in temperature.

I hope this information has answered your questions
Many thanks again
The Home Engineer

Quote:

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Originally Posted by Okapi

Nice work, and a lot of patience to make them!!!
Do you have tested silver(I have copper soldering too) soldering with sheet solder, since I use that they are a lot of difficulties which disappeared, especially for soldering hard metal on tools or replacing hard metal teeth on saw blades.

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Hi Okapi
I am not sure what tested silver is?
I have used copper to copper which is not as nice as silver soldering as it doesn't flow as well. I have never used the solder that is suspended in flux which is like a paste you paint on. This tends to be used in jewellery making but I definitely would like to give it ago just to see what type of results I could get but very expensive to buy. I do use different melting point solders on some fabrications so I have less chance of effecting the previous joint but generally as long as there is no flux present the previous solder joints require a higher temperature to remelt the joint.
Many thanks again
The Home Engineer

Hi HomeEngineer,

Thanks for answering my soldering questions. After rereading your text, especially the second example, I now realise that your soldering technique allows you to: a) make complicated parts which would be much more difficult to machine in one piece and b) assemble them without the need for special fasteners. You can probably tell from my questions that my soldering experience is quite limited. This method of fabrication – assembly by soldering can clearly produce quite sophisticated components.

Gary Kingsep

Hi Gary
practice is the only way to improve silver soldering and watching the flux change state is the cheapest way because you can do this without using solder on different scrap pieces of material just to get use to the temperature and flux change. Then when confidence in this the solder can be introduced.
Any questions please ask.
The Home Engineer

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Originally Posted by thehomeengineer

Hi Okapi
I am not sure what tested silver is?
I have used copper to copper which is not as nice as silver soldering as it doesn't flow as well. I have never used the solder that is suspended in flux which is like a paste you paint on. This tends to be used in jewellery making but I definitely would like to give it ago just to see what type of results I could get but very expensive to buy. I do use different melting point solders on some fabrications so I have less chance of effecting the previous joint but generally as long as there is no flux present the previous solder joints require a higher temperature to remelt the joint.
Many thanks again
The Home Engineer

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Hi, I've controlled on the box if it is something about silver grade, but it's a very old packaging from Castolin and it was originally for assembling hard metal on lathe tools, in my opinion as I use it for jewellry too for my wife it's about 0,750 and very white, it's a band of 0,1mm X 20mm, if you want I can send you a part for proofing, I have enough for about 50 years…
It's very convenient because you just put a part of the sheet between the parts you want to assemble at the dimension of the contact between them (with 1802 flux in my case) and you heat it, no cleaning and a very esthetic assembly.
I have the same in copper and I suppose it was for the same purpose, the difference is more on the heat transmission than the resistance of the soldering because I just have to heat more with copper than with silver and I see no evidence of a difference in my purpose.

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HE, Thanks for the tutorial.

is it best to use distilled water to thin flux, or is it not that important?

Very, very nice.
In your final assembly pictures does the dark mat finish come from the blasting only, or was there some kind of color/heat treatment used that gives it that nice gunmetal look? Are you showing this build in some other forum I can follow along?

Water? Thin the flux with alcohol! Water boils away and splatters the flux, alcohol burns off, leaving the flux whete it should be.

Soldering & brazing bond materials in a manner similar to glue and wood. Increased heat, cleanliness, and flux promote the expansion of parent metal to where the solder or braze rod penetrate a few bare thousandths. An ideal gap is .002 -.004. A proper joint displays a thin silver line without pits or empty spots; a familiar application is mounting of shotgun ribs and front sights of rifles. The silver doesn't take bluing, so extra care is taken; that line displays craftsmanship.

Like lead solder, various melting temperatures of silver help assembly projects, especially prevalent in jewelry, starting out with higher temps first. Other way around is more like a house of cards.

Quote:

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Originally Posted by gatz

HE, Thanks for the tutorial.

is it best to use distilled water to thin flux, or is it not that important?

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Hi gatz
Thank you for the message.
I use standard tap water to mix flux and this works fine. Add a small amount of water at a time to the flux powder and mix until it is slightly runnier than tooth paste.
Hope this answers your question.

Quote:

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Originally Posted by petertha

Very, very nice.
In your final assembly pictures does the dark mat finish come from the blasting only, or was there some kind of color/heat treatment used that gives it that nice gunmetal look? Are you showing this build in some other forum I can follow along?

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Hi petertha
The finish is from the shot blasting. I use this to give a good key for painting. If it was a pressure fitting or vessel it would be placed in my acid bath to clean of the flux. The reason for this the shot blasting can remove some of the solder and comprise the solder joint. For everything else the shot blasting method is quick and gives a great finish. Hope this helps and answers your question.

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Originally Posted by Murph1090

Water? Thin the flux with alcohol! Water boils away and splatters the flux, alcohol burns off, leaving the flux whete it should be.

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Hi Murph
I have never used alcohol but will definitely try it. The reason I use water is I can mix a small batch of flux and as long as I put in a sealed container it lasts for months. Flux is not cheap and I never seem to be able to mix the actual amount I need so this works for me. I have not had the issue with the flux splatter? Do you place the heat directly on to the joint as this will cause a problem with the flux as the heat from torch can burn the flux off before the material is up to the correct temperature. This is more prevalent on larger assemblies and I apply the heat uniformly around the joint and on the largest material section and allow the heat to move toward the joint. But I am very interested in the alcohol especially on smaller assemblies.

Quote:

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Originally Posted by thehomeengineer

Hi Murph
I have never used alcohol but will definitely try it. The reason I use water is I can mix a small batch of flux and as long as I put in a sealed container it lasts for months. Flux is not cheap and I never seem to be able to mix the actual amount I need so this works for me. I have not had the issue with the flux splatter? Do you place the heat directly on to the joint as this will cause a problem with the flux as the heat from torch can burn the flux off before the material is up to the correct temperature. This is more prevalent on larger assemblies and I apply the heat uniformly around the joint and on the largest material section and allow the heat to move toward the joint. But I am very interested in the alcohol especially on smaller assemblies.

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I'm learning from this thread, so I am not even a novice. It seems that if you used alcohol, perhaps denatured alcohol that is refined more, you could still store the flux in a sealed (alcohol proof) container, and if some of the alcohol evaporates, you can just add more. The flux will still be there, but it will just be thicker.

Quote:

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Originally Posted by Rikk

I'm learning from this thread, so I am not even a novice. It seems that if you used alcohol, perhaps denatured alcohol that is refined more, you could still store the flux in a sealed (alcohol proof) container, and if some of the alcohol evaporates, you can just add more. The flux will still be there, but it will just be thicker.

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If you want to try alcohol use Methyl Hydrate. It is pure alcohol. Sometimes sold as gasoline antifreeze where the climate is colder.

@ thehomeengineer

I'm slightly dyslexic as well. And I have close friends and relatives who are. They are all capable intelligent folks. I think sometimes it is a blessing/curse. We see the world differently. And that's what allows us to do things that other people are either scared of trying or simply do not see the possibility of accomplishing.

I liked your tutorial on soldering. My German grandfather taught me how to solder. Clean, clean and clean again. Then like you say flux, flux and flux again.

The key is indirect heat. Not the flame as you point out so well. Heat the surrounding area that oyu want to solder to and let the heat wick into the joint area.

Thanks for tip about soldering stainless. I will be finding that flux.

Always enjoy your tips and techniques.

Mark

Hi Mark
Thank you for the kind words. HMT is a great place to gain additional advice, tips and advice on all aspects of engineering and wood working. I appreciate the feedback on my posts.
The Home Engineer

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Originally Posted by thehomeengineer

Hi Mark
Thank you for the kind words. HMT is a great place to gain additional advice, tips and advice on all aspects of engineering and wood working. I appreciate the feedback on my posts.
The Home Engineer

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Thanks! I am a rather accomplished cabinetmaker/carpenter. Have done this for nearly 40 years. An amateur machinist with a broad variety of experience but no claim to knowing exactly what is what is every application.

I learn from many. And I'm experienced enough to know when people are experienced themselves or if they are just posting something they barely understand.

Thanks again.

Quote:

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Originally Posted by petertha

Very, very nice.
In your final assembly pictures does the dark mat finish come from the blasting only, or was there some kind of color/heat treatment used that gives it that nice gunmetal look? Are you showing this build in some other forum I can follow along?

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Hi petertha
I have my own website you might like to have a look at. It has different projects I have completed or still working on. Please take a look at Practical Engineering
The Home Engineer

I have progressed the clutch linkage and have fabricated some of the levers using silver soldering.

I have included some photos of the process I use to machine tapers on levers etc.
To machine the tapered lever, the two holes are drilled at the correct pitch in the stock material. Then the coordinates are calculated to set the workpiece at half the required inclusive angle. A sacrificial piece of material is then drilled tapped at these calculated coordinates to set the piece at the correct angle. The lever can then be clamped and machined to produce the first taper. To complete the process the lever is flipped over and the second angle machined and then filed using file buttons to the final shape. The photos below will hopefully make things clearer.

Attachment 34953 Clamp screws and lever ready to be filed

Attachment 34954The completed parts ready for soldering

Attachment 34955 Sacrificial material drilled to set angle

Attachment 34956 Attachment 34957 Attachment 34958 Machining first taper

Attachment 34959 Second taper completed

Attachment 34961Completed taper lever

Attachment 34960 One of the soldered links in place on the engine

Thank you for viewing
The Home Engineer

Thanks!
That is a lesson I am just learning - take a few extra minutes to make a jig.
I have a couple chunks of metal with all sorts of holes in them - I don't recall what most of the are for now, but they were in just the right place when I needed them.

Quote:

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Originally Posted by mwmkravchenko

If you want to try alcohol use Methyl Hydrate. It is pure alcohol. Sometimes sold as gasoline antifreeze where the climate is colder.

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Thanks for the tip - I'll have to try it. I currently use ethyl alcohol to replenish my paste solder (used for electronic surface mount soldering). Methyl Hydrate (methanol) used to be widely available in RC hobby stores for glo-plug engines. Electric has replaced most glo-plug engines but there still some that use them.

@ thehomeengineer

Thank you for the post. I have learned a few things from your posts and enjoy your craftsmanship. I also liked your soft-jaws and wire cutting guillotine on your website.

FEM

The upside to alcohol is you can brush it on and have a layer of dry flux between the parts, where it can't burn off from the torch heat.

When I do parts, I use air-acetylene torch, that way you can't overheat your part, and I use a large tip, and lower pressure, so the flame doesn't blow small parts or the solder out of position. If I keep my distance with the torch, it all heats up evenly and joins near seamlessly.

Murph

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Originally Posted by Karl_H

Thanks!
That is a lesson I am just learning - take a few extra minutes to make a jig.
I have a couple chunks of metal with all sorts of holes in them - I don't recall what most of the are for now, but they were in just the right place when I needed them.

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I probably look at every part as candidate for a jig or fixture. At the same time, quantity [and then repeated use] is what justifies how sophisticated a jig/ fixture is called for.
If the plan then calls for tooling, one additional feature is worthwhile; the means to remount and locate via a reference feature [a pin, a step, a hole...etc]

The clutch linkage is nearly complete and I thought I would share how I fabricated the shaft and made the the box housing with different soldering techniques I use.

The box is relatively straight forward as it is screwed together and a mounting flange at the bottom. However screwing matting faces together is not great for silver soldering as there is no gap for the solder to capillary into. To over come this I file notches and grooves where I want the solder to flow. This doesn’t give satisfactory joints for pressure fittings but is great for fabricated components. The notches and grooves allow the solder to penetrate the joint as can be seen in the photos below.
Attachment 35014 Components to be silver solder together.

Attachment 35015 Filed notches can be seen on the inner part of the flange.

Attachment 35016 Flat plates that are to be screwed to top bearing block.

Attachment 35017 All shot blasted ready for assembly and fluxing.

Attachment 35018 Top bearing housing fluxed ready to accept plates.

Attachment 35019 The seems are also fluxed on the inside.

Attachment 35020 Base flange is a tight push fit over plates.

Attachment 35021 Attachment 35022 The photo shows that the solder has penetrated the base flange joint.

Attachment 35024 Attachment 35025 The heads of the screws are filed off.

Attachment 35026Completed box housing for clutch linkage.

The shaft is made from a commercially available stainless steel 8mm diameter 4 start thread and a brass flanged nut to suit.
As this requires a flanged section this is rough turned over size and silver soldered in place. The shaft and the flange section can then be placed in a collet and turned true to each other and to size. The shaft is 3/16”diameter and the flanged section drilled 0.004” (0.1mm) bigger to create the gap for the capillary action.

Attachment 35027 Shaft and flange

Attachment 35028 Again to stop the solder flowing we’re it is not needed the paint pen is used.

Attachment 35029Attachment 35030 A silver soldering ring is bent up and placed on the joint and fluxed.

Attachment 35031 Heat is applied to the largest section and the heat draws the solder into the joint.

Attachment 35032 Completed shaft awaiting top bearing and locknuts.

Thank you again for viewing and hope this will help those starting out silver soldering.

The Home Engineer

Nearly on the final stretch of the clutch linkage. The last of the fabricated parts are the two dog bone links which again are a silver soldered fabrication. The most important thing is that the links have both the same hole centres (pitch). To achieve this a scrap piece of material is drilled and tapped at the correct pitch and the ends of the dog bone linkage are held in position with countersunk screws and the tie bar fitted into drilled through holes. The fabrication is completed by soldering the joints.

Attachment 35041 One dog bone link machined ready for soldering.

Attachment 35042 Soldering jig

Attachment 35043 Screws painted to prevent solder contact.

Attachment 35044 Soldering completed.

Attachment 35045 Removed from jig.

Attachment 35046 Cleaned up using shot blasting and the holes need to be reamed.

Attachment 35047 Completed assembly awaiting operating handle. (Not sure if you make single crank or wheel type).

Thank you for viewing
The Home Engineer

It's very interesting to see how you make them by pair, soldering in an oven like those used by dentist can be a good alternative for a cleaner finish with less work after soldering, have you never tested the protection coating for a cleaner heated surface with less oxydising ?

Hi okapi
thank you for your comment. Correct me if I’m wrong but I think you are talking about a vacuum furnace which prevents oxidation and the need for flux. This is very specialised piece of equipment and has it drawbacks like brass can’t be used as the zinc is removed during the process. Also size of furnace and cost. The acid bath and the shot blasting cabinet I use are adequate and cost effective for the jobs I do. Please correct me if I have miss understood.

No, I'm simply speaking of the very cheap furnace used in the past for the dentistry mechanical use which are no more usable with new norms about sterilization etc.
They can go to 1'200° C and are generally less than 200 €, they can be use with inert gas generally by a very simple hole in the back but for me using borax is less expensive, I have two of them, one used for oil or water hardening and the other for carbon hardening with powder which make a lot of smoke and leave some residues in the furnace.
Using the hole for the gas introduction they are regulated by a captor and an electronic command unit.

I have never considered this but am always interested in other ways of achieving results. At 200€ a bottle of inert gas and another piece of kit to store in an already crammed workshop I don’t think I can justify the outlay. Have you had success using this method?

I'm using this technique since I was an apprentice, we use that for small pieces or for pieces which doesn't be cleaned, but near never with inert gas, just with borax or in special ignifugated bags for medical components, What is expensive with inert gas is the bottle but you can find small bottles very cheap made for small soldering units in the discount stores normally, here it's a current thing, for me I use a bottle I've bought at one time and it cost me about 40$ for a full new one and it's for two years approximately.

If you don't happen to have a paint marker available, another material you can use to prevent silver solder from sticking is correction fluid also known as "White out".
It's a opaque liquid that dries after it has been applied and was used to mask text errors on paper.

Cheers
Willy