Subject: Re: Epoxy vs. Silver Soldering

From: "D.E.Hockin" <[email-masked]>
Date: Wed, 10 May 1995 12:40:50 GMT

William Kaukler <[email-masked]> wrote:
>I have epoxied things to a gun barrel.  It is is a very bad idea  When I   
>was younger, and epoxy was still a novelty, it seemed a good idea.  The   
>universal solution, a panacea. 
>How wrong I was, brazing with metal is (as others have said) far stronger   
>than plastic (which is what epoxy is).  At the same time, don't beleive   
>people who claim welds or brazes are as just as strong as the original   
>ie. as good as new.  Joints of any kind are always the weakest parts of   
>anything. 

Not so! A proper welded joint should be as strong as the parent metal.

Also, an epoxy joint, properly made, CAN be STRONGER than the parent
 material - it just depends on that material! You can epoxy ceramic
 materials, and if you break them again, the break  will be anywhere
 BUT at the epoxied joint. I have proved this with soft and hard ceramics,
 and with glass. Epoxies are used in  industry for structural
 joints in steel and in aluminium alloys. In France and Britain,
 prestressed reinforced concrete bridges, e.g. the motorway bridge near
 Le Havre across the Seine, and in Britain the Second Severn Crossing,
 have all the units glued together with epoxy, the contractors using
 different resins for differing daily temperatures - one mix works
 nearly down to freezing point. I used to rebuild broken squash rackets
 with a combination of 1mm hardwood 3-ply and Araldite epoxy - the result
 was as strong/stronger than the original - they didn't break at my
 repair! The restringing serviceman used to lean on the frame very heavily
 before agreeing to do the stringing - he too didn't believe at first
 that a repair could be that strong.

>The reason the epoxy was no good is the differential thermal expansion   
>problem.  I lived up north and took the gun outside in the cold only to   
>find the epoxy broke off. 
> 
Thats not the "fault" of the epoxy, just the choice of the wrong
 technique for that particular job. Put the gun in too cold a climate,
 and it also might snap in two! And howabout the effects of the red-heat,
 needed to be able to silver solder or braze, upon the temper of the
 barrel steel? That surely cannot have improved the metal? I would
 have thought that those things ought to have been held together with
 screw or bolts, not glue, whether a metal or a resin "glue".

Dave.

-------------------------------------------------------------------
[email-masked]     | "my thoughts are mine alone, and not
			   |  those of the University"
                           |
                           | But I wouldn't mind betting they've
                           | someone working on that already!
------------------------------------------------------------------

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From: [email-masked] (Tim Kirby)
Date: 8 May 95 19:16:20 CDT

The Rifleman ([email-masked]) wrote:
: How does the bonding strength of an epoxy like Brownell's ACRAWELD compare
: to the bonding strength generated by silver soldering?  Bear in mind the
: epoxy can be applied to the entire contact patch, whereas the silver
: soldering can only be applied the joint between the two pieces as
: externally accessible.

The question is probably unanswerable as stated since the size of the joint
and the materials being joined are not specified.

A properly silver soldered joint would be heated such that the solder runs
between the surfaces and has the same contact area as the epoxy would.

I think I would probably vote for silver solder in the case of two pieces of
brass with a contact area of 1" square under tension, for example.

What is the context of the question?

Tim
--
Tim Kirby                    - [email-masked] -                +1-(612)-683-5390
Software Division System Support ________________ Cray Research, Eagan MN, USA
----------------- Ask not for whom I speak - I speak for me ------------------
If you are sure you understand everything that is going on,
you are hopelessly confused...                                - Walter Mondale

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From: [email-masked] (The Rifleman)
Date: 9 May 1995 02:21:06 GMT

>What is the context of the question?

Well, a couple of different projects.  One would be a muzzle attachment
on a 16" barrel.  I.e., a compensator slips over the muzzle and must
be held in place.  The choice is either epoxy or silver solder.

In another case, a piece of brass tubing will be used to decrease the
diameter of a hole used to pin two parts of a gun together.  In this case,
there should be no great shearing (sideways) force, except when the pin
is inserted and removed.  During ordinary operation, the force (the load
borne by the pin and hole) will be a compression force through the
piece of brass tubing and bonding material.

-- 
----------------------------------------------------------------------------
 "If you're on a confiscation team, before you kick in the next gun owner's
        door, you've got to ask yourself. . . . Do you feel lucky!?"
---------------------- NRA  Libertarian Party  FIJA ------------------------

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From: William Kaukler <[email-masked]>
Date: 9 May 1995 18:03:42 GMT

--  
William F. Kaukler, PhD., Met. & Mat. Sci.          phone 205-544-0693 
The University of Alabama in Huntsville 
Center for Microgravity and Materials Research; Huntsville, AL 35899 
and at NASA, Marshall Space Flight Center, Alabama 35812

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From: [email-masked] (Tim Kirby)
Date: 9 May 95 22:30:38 CDT

The Rifleman ([email-masked]) wrote:
: Well, a couple of different projects.  One would be a muzzle attachment
: on a 16" barrel.  I.e., a compensator slips over the muzzle and must
: be held in place.  The choice is either epoxy or silver solder.

Urgh. I plead complete ignorance in the art of applying heat to machined
tubes that will contain explosives. I assume that brazing of some sort is
appropriate in such a situation, but I have to believe that there are
techniques in heating the barrel so as not to distort it... if distortion
is a danger. I was always under the impression that things hung on the
end of barrels were attached by screw threads... but what do I know?

: In another case, a piece of brass tubing will be used to decrease the
: diameter of a hole used to pin two parts of a gun together.  In this case,
: there should be no great shearing (sideways) force, except when the pin
: is inserted and removed...

For a cylindrical type contact, how about a commercial loctite type
product? I would expect there to be something suitable (I think I typed
all the loctite data in and posted it once, a long, long time ago :)
for such an application. Or even a press fit?

I would not have thought an epoxy appropriate for either application,
personally.

I should have underlined in my original response that generally the silver
solder is going to provide a superior joint, but there is always the
assumption that the joint is made properly...

Tim

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From: David Josephson <[email-masked]>
Date: 10 May 1995 06:30:17 GMT

In <[email-masked]> [email-masked] (The Rifleman) writes:

>How does the bonding strength of an epoxy like Brownell's ACRAWELD compare
>to the bonding strength generated by silver soldering?  Bear in mind the

Poorly. Acraweld is good epoxy, but it's still glue.

>epoxy can be applied to the entire contact patch, whereas the silver
>soldering can only be applied the joint between the two pieces as
>externally accessible.

I don't think so. Properly applied, silver solder will be drawn into the
whole contact area by capillary action.
-- 
David Josephson / Josephson Engineering / San Jose CA / [email-masked]

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From: [email-masked] (Scot Heath)
Date: 10 May 1995 16:28:05 GMT

: In another case, a piece of brass tubing will be used to decrease the
: diameter of a hole used to pin two parts of a gun together.  In this case,
: there should be no great shearing (sideways) force, except when the pin
: is inserted and removed.  During ordinary operation, the force (the load
: borne by the pin and hole) will be a compression force through the
: piece of brass tubing and bonding material.

You may want to consider Loctite retaining compound.  It is designed
specifically for this type situation.  They have 4 choices:

Retaining Compound 609 - 100-150cP viscosity 
                         .005" gap filling ability
                         3000 psi shear strength
                         recommended for mounting close fit bearings and
                           bushings

Retaining Compound 620 - 7000cP viscosity 
                         .015" gap filling ability
                         3000 psi shear strength
                         -65 to +450 deg. F continuous service range
                         recommended for retaining cylindrical parts, 
                           high temperature applications

Retaining Compound 680 - 1250cP viscosity 
                         .015" gap filling ability
                         4000 psi shear strength
                         -65 to +300 deg. F continuous service range
                         recommended for retaining cylindrical parts

Quick Metal -           1,200,000cP viscosity
                        .020 gap filling ability
                        4000 psi shear strength
                        -65 to +300 deg. F continuous service range
                         recommended for retaining cylindrical parts, 
                           loose fitting

For more information, give them a call at (905)-890-6511

-Scot

--
DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER

Everything I write is my opinion only.  Nobody else would want it.

DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER_DISCLAIMER

Scot E. Heath                          "Nothing beats turning clay to dust."
Fort Collins, CO
[email-masked]

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From: [email-masked] (Norman Yarvin)
Date: 11 May 1995 01:33:24 -0400

[email-masked] (Tim Kirby) writes:
>is a danger.

There's generally no temper to ruin on the barrel; they're
usually soft steel.  Thus distortion does not pose a safety
problem but only an accuracy problem.  In addition a (slightly)
bent barrel will provide the same level of accuracy; it's only
when the bore diameters change that accuracy deteriorates.

[email-masked] (The Rifleman) writes:

>Ok, I've gotten recommendations in favor of locktite now from two people.
>Is the chemical bonding formula of locktite stronger than the one present
>in epoxy?  (You seem to imply it would be a more suitable joiner.)

The advantage of loctite probably isn't in raw strength, but
rather in shock and temperature resistance.  There are many
different types of loctite, with varying bonding strengths,
curing speeds, viscosities, etc.  The most commonly sold
varieties are for threaded joints and are not suitable for
joining cylinders.  I recommend that you get a reference that
lists a lot of varieties (the MSC catalog is not bad), and
decide which one is most suitable.

--
Norman Yarvin						[email-masked]
 "People say I am like Captain Bligh.  I am disappointed.  I considered
  myself more like Attila the Hun." - H. G. Rickover

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From: [email-masked] (The Rifleman)
Date: 10 May 1995 20:37:47 GMT

>end of barrels were attached by screw threads... but what do I know?

Quite true.  The problem is that threading the barrel of a semi-auto rifle
is in many cases illegal, whereas attaching a compensator (by some other
means) is not.

Thanks in advance...
-- 
----------------------------------------------------------------------------
 I pledge my life to the 2nd Amendment and to the freedom for which it stands;
 one right, created by God, indivisible, with liberty and justice for ALL.
---------------------- NRA  Libertarian Party  FIJA ------------------------

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From: [email-masked] (Tim Kirby)
Date: 13 May 95 00:42:17 CDT

The Rifleman ([email-masked]) wrote:
: Ok, I've gotten recommendations in favor of locktite now from two people.
: Is the chemical bonding formula of locktite stronger than the one present
: in epoxy?  (You seem to imply it would be a more suitable joiner.)

Stronger is one of those, uh, funny words. Loctite prodicts are designed to
lock cylindrical surfaces and a jolly good job they do of it. They have well
documented characteristics for particular scenarios and seemed to be the right
tool for the job described. I believe they are at least related to the
cynoacrylate (so-called "super glue") adhesive family. Like any other glue,
surface preparation is a key factor; chemical cleanliness is absolutely
essential to get a good bond.

Tim

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From: [email-masked] (TaiJi3)
Date: 25 May 1995 12:50:42 -0400

The simple truth is NO adhesive is as srong as silver solder. But
depending on joint configuration and possible heating
restrictions,adhesives can workfor some jobs. We need to know what the
joint is like first though
TiJi

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From: [email-masked] (PeterWRowe)
Date: 26 May 1995 03:57:37 -0400

>restrictions,adhesives can workfor some jobs. We need to know >what the

One thought that does occur to me, I situations where a joint will be
subject to long term vibration or flexing, some adhesives may be
preferable, though I'd suspect that epoxy isn't one of them.. I'm thinking
of some of the foam cored pressure sensative adhesives.  The industrial
variety of the little green square 3M sells in hardware stores are used,
for example, in laminating aircraft skins to the ribs, in preference to
welds or solders, because the adhesives don't concentrate stresses at the
joint, absorb vibration and flexing without as much eventual cracking,
etc. and aren't as prone to such things as stress corrosion failure and
the like. 

One other thought, the heat sensitivity of epoxies can also be thought of
as an easy way to provide for disassembly at a later date of a joint that
might need such.  a little heat and it just pulls apart.  A lot easier
than unsoldering something.  Then, service completed, clean and reglue. 
Good as new.  Sometimes this might be a desirable quality.

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From: [email-masked] (Barry Workman)
Date: Tue, 30 May 1995 16:38:37 GMT

Ah, epoxies were developed by and for the aerospace industry.  We
glued wing sections and control surfaces with epoxies on the F-100
back in the late '60s.  Douglas Aircraft (before the merger with
MacDonald) used epoxies for rib assemblies on the DC-8 an aircraft
that is still flying.
-- 
    - Barry Workman