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Member postings for CuP Alloys 1

Here is a list of all the postings CuP Alloys 1 has made in our forums. Click on a thread name to jump to the thread.

Thread: Brazing teeth
26/03/2019 09:21:48

Hi Grant.

Silver soldering cast iron to itself or stainless or copper alloy is no problem. You simply need to make a slight adjustment to your technique to ensure that you stick to the basic principle of brazing - capillary flow.

For more information see the book or give us a call.



Thread: Silver soder joint breaking
25/03/2019 09:39:05

A properly made silver solder joint will certainly withstand the stress of parts stuck to a jig by flux residues!

If the joint failed there is something amiss. Examine your joint design, fluxing, heating technique.

To answer some of your questions;

1) any jig used must allow for the inconvenience assembly to move. That's a contradiction of terms but if the components can't expand they will distort. Redesign your jig.

2) the jig nor the alloy will cause a weak joint but thermal stresses during cooling might.

3) silver solder does not like lead. It affects the fluidity.

More information on this and other silver soldering issues can be found in the book "Every Thing You Wanted to Know about Silver Soldering but were afraid to ask". Available via CuP Alloys.


Thread: Making split bronze bearings [ silver soldering ]
24/03/2019 08:41:48

Hi David.

Paste is an expensive solution to the problem although the technique is sound.

Use a paint. It is cheaper, easier to apply and you will use less of it.

Readily available from any good supplier.



Thread: Silver soldering bronze
21/03/2019 15:51:36

Hi Martin.

At the risk of repeating myself, if the silver solder or soft solder doesn't "wet" you have a flux problem.

Use the right flux.

Aluminium alloys can be soft soldered.

Aluminium bronzes can be readily silver soldered.

Ring us for more information.


Thread: Silver soldering a blind 'mortise and tenon' joint.
06/03/2019 12:24:41

Hi Robin.

See private message for my views on "tinning"



05/03/2019 08:05:26

Hi Robin.

Michael's approach is underestimated- it will work!

It simplifies the heating process by creating the ideal heat pattern to promote that all important capillary flow. When the 455 melts and flows, the capillary forces will centre the spigot in the hole.

The weight of the spigot and the capillary forces will ensure that the spigot sinks into the hole. Just make sure that your joint design allows for this.

No need to file flats on the spigot or worry about steam or flux entrapment.

Michael's approach underlines the simplicity of the silver soldering process when it is done correctly.



Thread: Silver soldering bronze
26/02/2019 09:48:46

Hi Martin.

Silver solder not wetting is always a flux problem. Silver solder not flowing can be due to heat pattern, joint gap, flux or contamination eg lead from a bronze.

Give us a call for more information. It's a quicker and easier way to communicate than the forum.

Looking forward to hearing from you.


Thread: Brazing after milling whilst preserving accuracy
26/02/2019 09:39:02

Keep any distortion to a minimum by firstly keeping the brazing temperature to the minimum. Use the 55% silver alloy eg 455.

Secondly use a thinner rod that requires less heat from the joint for it to melt. Consider 1.0 or 0.7 or 0.5mm wire.

Heat the components slowly to bring the joint up to temperature evenly. Consider using a long life flux eg HT5. Re-examine your heating technique

Cool the joint slowly in dry sand or mica.



Thread: Tube Seam
15/02/2019 10:24:08
Form the tube from sheet and silver solder a strap inside and along the seam. Use a strap width of 6x it's thickness.
Easier to use seamless tube though!
Thread: Silver soldering problems.
17/01/2019 09:06:10
Hello Brian.
Suggest that you use 455 alloy say 1.0mm dia.

Direct the heat more into the thicker, heavier component.

For details on alternative burners see the sievert range on

You may also consider using a longer life flux ie HT5.

The cause of your difficulties is very common - you have veered away from the basic principle of brazing of using capillary flow to effect your joints.

For more information and avoid any future difficulties see "The Guide to Brazing and Soldering" available via the website.

15/01/2019 19:38:13

Ooops !

Typo in the post.

Should read "Sievert 2941burner"


15/01/2019 10:01:07

Hello Brian

It looks like Jason has a point. From the picture it looks like the alloy has been overheated. The "gas" coming off the alloy (if it is easiflo - and you don't know?) is likely to be cadmium fume.



I suspect that you are preferentially heating the alloy. Steel does not conduct the heat quickly into the joint area. The flux doesn't work and the alloy doesn't penetrate. So you then heat the alloy to get it to flow. Ring any bells?

Heat the joint. Not the alloy.

Get the joint hot. Watch the flux to see what joint temperatue you have. Let the alloy get its heat from the workpiece.

Fit a smaller burner than the Sievert 2901 that you are using. Be patient while heating. Make sure that the joint is up to temperature.

Change to a cadmium free silver solder.

Burners, alloys and technical information in an excellent book is available from CuP Alloys on line or at Ally Pally this week.

Take care.


PS You don't get information like this from ebay, car boots or many other sellers of silver solder.

What has your supplier had to say? Let me guess!!!!!!!!!!

Thread: London Model Engineering Exhibition - Alexandra Palace
08/01/2019 15:20:14

The most knowledgeable source of information regarding silver soldering and brazing for the model engineer is there.

Just ask Glen or Shaun on the CuP Alloys stand.

Regards to all


Thread: Soldering
11/12/2018 12:10:10

Hello Iain.

Not to be sidetracked I return to your original request about soldering.

First off - neither of the two fluxes in the picture are suitable for use with what appears to be silverflo 40. There is what appears to be a JM label but unless there has been a dramatic turn around I do not believe that the material was supplied to you by JM. They do not supply it by the rod! And CuP do not use JM labels!

So what advice does your supplier offer? I would be interested to know.

Secondly. You should be able to melt the silver solder with a plumbers torch - as long as you are generating enough heat.

If the steel is a dull red the silver solder should melt a 40% silver cadmium free alloy

Thirdly, if you can melt the silver solder but it doesn't flow then change your flux to one with a longer life eg HT5 from CuP Alloys.

Fourthly, if you can't melt the silver solder then use a lower melting point alloy eg 455 from CuP Alloys.

Why do I keep plugging CuP Alloys - because they are the company that can supply good quality materials and give the technical help to get the right results.

Silver solder is expensive ..... especially when it doesn't work!


Thread: How does solder stick ?
09/12/2018 12:59:09
What a marvelous response from Robin.Brilliant!A terrific picture that shows what happens and illustrates just why thin solder and brazed joints are stronger. Thanks for your contribution to the campaign.
Thread: Lead Bearing Solder is Banned
08/11/2018 13:46:24

Article 67 of REACH shows that legislation has been passed banning the sale of any lead bearing materials to the general public. This includes soft solder.. The maximum allowable content of lead is 0.3%. Above this figure, all such materials are regarded as TOXIC

As far as I am aware, very little effort has been made to advertise this legislation. The onus is on individual companies to keep abreast with such legislation via government websites.

I have it on very good authority that the H&S Executive working in tandem with the Trading Standards Authority have tried to enforce this legisation.

I repeat, the legislation, only applies to the general public. It does not apply to any professional organization or company. I believe the argument is that any tradesman is not at risk but the man in the street is. The former knows what he is doing- the latter doesn't.

During a visit from the authorities, it was pointed out that far greater quantities of lead bearing solders are readily available on the High Street to the general public, from several warehouses, merchants and manufacturers. The investigating team was directed to these outlets.

They were not aware of this situation! They left to visit one source immediately.

Because, they do not want to be seen as discriminating against small companies, they have held off any legal action until until they can bring all outlets into line - a logistical nightmare!

So, it is coming.

CuP Alloys are already investigating other alloys that offer similar soldering characteristics in order to meet any demand from the model engineer.

It is not illegal to use lead bearing solder. The law prevents it from being sold or placed on the market - that means sampled or given away. It is very similar to the legislation forbidding the sale of cadmium bearing silver solders. After all, it emanates from the same European capital.

Where will it end? Free cutting phosphor bronze and mild steel are in their sights!

There will be no further comment from me!


Thread: Brazing Mild Steel
02/11/2018 10:08:53
A couple of points to add...
I said during my talk at the Fosse that cleaning of the joint is not your job - it's the function of the flux. The joint must be clean at brazing temperature not at room temperature. You cannot achieve this but the flux can and will. Using citric acid is a waste of time. Use it if you wish but just make sure that you wash it off. The heat from the torch will leave a deposit of citric acid salt that the flux will not remove. Result - poor joint!
The amount of detergent used in making the paste has no deleterious effects.

I also stressed at my talk "ask questions,- don't be afraid to ask". Why didn't you?

There is more information and technical help on silver soldering and/or brazing at CuP Alloys than eBay, Amazon,car boot sales, welding
distributers etc put together.

Why not use it?

At worst, you will be talking to someone who has been in this business for 24 years. Strike lucky and he has 49 years!

I'm getting old!

31/10/2018 09:22:28
Hi Bill,
Borax does not become effective until it reaches a temperature above the melting range of most silver solder.
So you have to overheat the alloy. Ok, you could, repeat could, make it work, but why go through the hassle?
A couple of quid buys you the right flux that enables you to do it properly.
28/10/2018 11:29:33


It is identical to soldering. It is only an undocumented international convention that distinguishes between the two. Quite simply, if you are making your joints at a temperature below 450 deg C then you are soldering.

Above 450 deg C then you are brazing.


IT HAS NOTHING TO DO WITH THE HEATING TECHNIQUE. Gas torch, furnace (vacuum or atmospheric), electrical resistance, induction are all viable heating techniques to produce brazed joints

Jet engines are brazed with gold/palladium brazing alloys.

Automotive components are brazed with copper and copper brazing alloys (this includes brass!)

Nuclear reactor components are brazed with nickel brazing alloys.

Steam boilers, bogies, clocks, are brazed with silver brazing alloys.

Look up the term "brazing" in any source and you will find that in the definition there are two words that repeat and those two words are "CAPILLARY ATTRACTION"


All too often silver brazing alloys and brass alloys are not used to braze two components together. They are used to stick two components together and block a hole and that is expensive. Look at some bicycle frames, office furniture and the multitude of joints made in steel using brass rod and oxy-acetylene torches.

I have supplied, in the past and for over 18 months, a company in excess of 200 kg per month of a silver brazing alloy that was used to do precisely that. The financial risk became too great and the orders were passed directly to my supplier.

The customer refused to change the joint design and to use the alloy as a brazing alloy.

In doing so they failed to take advantage of the many technical advantages of using the process. Silver solder, because of the price, is only used because it satisfies a technical requirement.

It will join a wider range of parent materials than welding.

It is carried out at lower temperatures - less distortion.

As a filler metal, it is more corrosion resistant.

It produces leak free joints.

It produces joints stronger than the parent materials.

It offers better strength at elevated temperatures.

It offers a good colour match to parent materials.

It can be carried out using relatively inexpensive equipment. Propane/air torches are fine.

If none of the above are important then save your money and use soft solder, or glue or screws!

In all cases, the use of a silver solder, despite its price, produces the cheapest cost per joint. If as an individual you can't reach this conclusion, you are are not using the product correctly. Examine your joint design (gap and length), examine your heating technique to get the alloy to flow precisely where you want it, examine the form in which the silver brazing alloy is being used. There is more than 1.5mm dia rod.

As regards, other companies ceasing to sell silver solder, I believe that was due in no small way to CuP Alloys. They passed on the benefits of their large buying power with German and Spanish suppliers to the model engineer and backed that up with good sound technical back up.

For more information, there is a book available from CuP Alloys.

"A Guide to Brazing and Soldering - everything you wanted to know about Silver Soldering but were afraid to ask"

I cannot speak too highly of it!



PS Brass strip and borax will produce excellent joints. But please "braze" with it and not simply stick the pieces of steel togerther

Edited By CuP Alloys 1 on 28/10/2018 11:30:45

Thread: A New Golden Age of Model Engineering Exhibitions
23/10/2018 11:14:59

But as Shaun has said prices are made as competitive as possible but that will not satisfy some.

True Story from the Midlands Exhibition.

"I'm not paying that. I'll wait and get it off the internet"

The product is not available, nor will be legally, on the internet. What he meant was,

"I'll wait til somebody robs you and I'll pay the thief"

There you go.


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