Subject: Re: brazing

From: [email-masked] (James Foster x2912)
Date: Wed, 26 Jul 1995 17:14:42 GMT

In article <[email-masked]>, [email-masked] (ErnieLeim) writes:
|> Silver brazing is a term usually applied to silver soldering with a silver
|> solder that has  a high silver content. The higher the silver content the
|> higher the temp needed to melt it and the greater the strength. High
|> silver content solders are also called hard solders and are mostly used to
|> fabricate jewelry.                 
|> Silver has better capillary action than bronze, so it pulls into smaller
|> gaps. It is considerably stronger than bronze.
|> It also is less likely to burn than bronze. This is when you keep the heat
|> too high for too long and burn the Tin out of the brazing bronze.
|> Oxy - acet. (3200 deg.F) works fine but it is a little on the hot side.
|> Oxy - Natural gas is a little cooler(2700 degF), and is the standard of
|> the jewelry business , but propane (2000 degF) is a little too cold for
|> anything other than soft silver solders or tin solders.

Good stuff, but the "propane won't work" statement is not correct. When
I worked for a musical instrument repair company we did all of our silver
brazing (hard soldering) with a compressed air/propane torch. Actually we
did all of our soldering with this torch. It can be turned down to give a 
very soft flame so as not to burn laquered brass when soft soldering, or
as hot as a standard propane torch. The key is the size of the object to
be soldered and whether or not the torch can supply the amount of heat
necessary to get the piece to soldering temp. in either a reasonable amount
of time or at all. For small parts like clarinet keys and the like this
torch will work well and quickly. Another poster suggested that if you had
an object the size and mass of a golf ball you are about at the limit
of propane. This sounds like a reasonable rule of thumb. I wonder how well
this style of torch would work with oxy/propane?  With a few valves and 
check valves it would be easy to switch from compressed air to oxygen.
Anyone have any ideas on how this might work, or is it too dependent on
torch design?  Otherwise this would give a quite large range of heat
available from one setup.

---

From: [email-masked] (James Foster x2912)
Date: Fri, 28 Jul 1995 16:11:37 GMT

In article <[email-masked]>, [email-masked] (David William Jenkins) writes:
|>  

|> >
|> 
|> Can't agree - I've silver-soldered a 40lb copper boiler (18" long
|> x 6" average dia) for my loco using a single propane burner.  No
|> particular problems. 
|> 
|> I was using the biggest burner made by a British company called
|> Bullfinch - it's about 3" diameter and sounds like Concorde on
|> reheat when fed at 60psi.  I froze my large gas cylinder to the
|> floor after 30 minutes, and used about 10 Kg of gas in that period.
|> 
|> The moral is - if you put enough heat in, and have enough
|> fire-bricks around, you can silver-solder big stuff.
|> 

David is absolutely correct. I was limiting my thinking and advice
to your average hardware store sized propane torch head. The flame
temperature is certainly hot enough so the limit is just how much
heat output the torch design/size is capable of and how much of that
heat you can keep in the piece being soldered.

---

From: [email-masked] (Joshua_Putnam)
Date: 27 Jul 1995 15:01:13 GMT

While we're on the subject of silver [soldering/brazing], does
anyone have a favorite mail-order supplier of brazing rod with a
good selection of alloys at reasonable prices?  

--

[email-masked]  is  Joshua Putnam/P.O. Box 13220/Burton, WA 98013
                   "My other bike is a car."

---

From: [email-masked] (ErnieLeim)
Date: 25 Jul 1995 03:32:53 -0400

Silver brazing is a term usually applied to silver soldering with a silver
solder that has  a high silver content. The higher the silver content the
higher the temp needed to melt it and the greater the strength. High
silver content solders are also called hard solders and are mostly used to
fabricate jewelry.                 
Silver has better capillary action than bronze, so it pulls into smaller
gaps. It is considerably stronger than bronze.
It also is less likely to burn than bronze. This is when you keep the heat
too high for too long and burn the Tin out of the brazing bronze.
Oxy - acet. (3200 deg.F) works fine but it is a little on the hot side.
Oxy - Natural gas is a little cooler(2700 degF), and is the standard of
the jewelry business , but propane (2000 degF) is a little too cold for
anything other than soft silver solders or tin solders.
Good luck and hope this helps
@---------------------------------------------------------@
                    Ernie Leimkuhler                                      

                  Stagesmith Productions                                  
                                          
                 Custom Metal Fabrication                                 
               
*    ABANA   SCA     AWS    USITT   IATSE local 15, 488   *
                        Renton, WA                                        
   
*"Rich gifts wax poor when givers prove unkind" the bard  *
@---------------------------------------------------------@

---

From: [email-masked] (David William Jenkins)
Date: Thu, 27 Jul 1995 22:23:45 GMT

In article <[email-masked]>, James Foster x2912 ([email-masked]) writes:
<deletia>

>|> anything other than soft silver solders or tin solders.
<deletia>

 Another poster suggested that if you had
>available from one setup.

Can't agree - I've silver-soldered a 40lb copper boiler (18" long
x 6" average dia) for my loco using a single propane burner.  No
particular problems. 

I was using the biggest burner made by a British company called
Bullfinch - it's about 3" diameter and sounds like Concorde on
reheat when fed at 60psi.  I froze my large gas cylinder to the
floor after 30 minutes, and used about 10 Kg of gas in that period.

The moral is - if you put enough heat in, and have enough
fire-bricks around, you can silver-solder big stuff.

David Jenkins              -- aka --             Lathyrus Computers Ltd
***********************************************************************
* All incorrect spelling and grammar is intentional.  Corrections are *
* superfluous and will be ignored.  So there.                         *

---

From: [email-masked] (Bob Neidorff)
Date: Fri, 28 Jul 1995 12:19:47 GMT

In article <[email-masked]>, "John W. Hall" <[email-masked]> writes:
|> I have a rather basic question I hope someone can answer. 
|>    "Brazing" I understand to mean the standard welding shop technique 
|> for joining two metals you can't or don't want to weld. It uses a 
|> coated brass rod that is melted and flowed into the joint. 
|>    "Silver soldering" I understand to mean a similar process using a 
|> silver based alloy instead of brass, and a separate paste flux, at 
|> lower temperatures but higher temp than soft soldering.
|>    What then is silver braze? Is this just another term for silver 
|> solder? or is it a nother alloy at a temperature somewhere in between 
|> the two?

Here's what I have read.  It may be inaccurate.

There's a temperature threshold.  I believe that it is 800 degrees F.
Above that is called brazing.  Below that is soldering.  Brazing
implies brass, so some people use the distinction "hard" vs "soft"
soldering for the same threshold.

Most brazing alloys melt above 1000 F.  Most soldering alloys melt
below 600 F.  This gives a wide region where no one works.  :-(

Silver Soldering is an oxymoron to purists.  The alloys used for
brazing that are high in silver are called silver brazes.  They melt
in the 1000 F range.  There are also soft solders which contain 
some small amount of silver, but these are not significantly 
stronger than other soft solders.  They are used for soldering to
items which have a high silver content, as they prevent silver
leaching.  They also have some other interesting properties, but
are not as strong as brazing or hard soldering.

To the best of my experience, silver brazing and hard soldering
require an oxygen + fuel torch.  I have never been able to get a
hard solder / silver brazing alloy to flow with propane or MAPP, 
even with a swirl combustion torch.  Some jewelers use a blow 
torch where they use their mouth to blow a controlled amount of
air into the flame to add oxygen, but I doubt that this would
be adequate for silver brazing, except perhaps for tiny articles.

If anyone has additional experience, data, ideas, or thoughts to
add, please share them.  Thanks.

-- 
Bob Neidorff; Unitrode Corporation  |  Internet: [email-masked]
7 Continental Blvd.                 |  Voice   : (US) 603-429-8541
Merrimack, NH  03054-0399 USA       |  FAX     : (US) 603-429-8564