silver soldering

[bluebayou]

Can anyone point me in the right direction about how to silver solder?  Is it any different from regular soldering?  I have just assumed that the solder's content was different.  I can't really find any good info on "silver soldering".

[gunnut69]

I'm far from a guru when it comes to silver soldering. It is similar to normal sweat soldering but the silver solders generally flow at much higher temps. James Howes book called 'modern gunsmithing ' gives a fairly good explanation.  The fluxes are much more important and in general corrosive. The usage for gunsmithing is very limited for general work as the temps are usually easily hot enough to alter the temper in even 4140..

[Flint]

True silver solder is a form of brazing.  There are several "low temperature" Silver Solders in the hardware stores that are not true silver solder, but are actually lower temperature than tin/lead solder.  They are not even close to being true silver solder, and will not adhere to stainless at all (I've tried it), perhaps not even carbon steel,  they do work on brass.  Avoid them.

You will probably have to find real silver solder at a welding supply or hobby shop, and the proper flux as well, which is quite different from lead solder flux, it is more akin to brazing and welding flux.  It melts down into a glass-like crust.  There are (or used to be, as I haven't done real silver solder in 30+ years) three temperatures of silver, low, medium and high, to allow joints to be made close together without loosening the previous joint. (start high).  There's a few hundred degrees between them.

Silver solder is the most common method of attaching front sights that aren't dovetailed or staked in place.  Particularly most common on a Single Action Colt or clone.  Unfortunately, the temperature required (dull red steel) of silver solder requires a reblue on a non stainless gun, and a repolish to remove the heat marks on the stainless.  Be carefull not to apply too much silver solder or it will run or fillet too much and make a brass-like outline around the joint that isn't professional looking on a blued gun.  One of the problems with some front sights, which I've heard more complaints aimed at Pietta, is they use too little solder, probably trying to prevent the solder showing against the blue, and the sights get knocked off too easily.

Silver solder can be done with a propane torch, you don't need a welding torch, though, if you're careful, you can use one.

Apply the flux between the parts to be joined, heat the metal parts 'til the flux melts, apply the silver solder wire to an edge of the joint opposite the torch, and when it melts, it should flow toward the torch. Aim the heat the largest part with the torch flame as if you play too much heat on the smaller part you'll overheat it

Silver solder is also available in a jar of ground solder powder mixed with flux as a paste, and for many applications is easier to use, as when the temperature reaches the melting point, it flows and you're done.  Of course the parts have to be clamped together some way to hold them in position through the process.

[trotterlg]

One other trick is to heat the end of the silver rod and then dip it into the flux powder, the flux will stick to the end of the rod and let you apply flux as you feed in the rod.  On an acetline tourch run a long "feather" so you don't have too much oxygen and oxidise the part you are trying to solder.  Larry

[bluebayou]

Once again, you guys have come through.  I am planning on using a propane or MAPP torch.  I do everything at the kitchen table more or less.  This would probably be done outside thinking about it.  Anyway, I want to fix a shotgun rib and to extend the tang on a knife that I am making.  I will go to a welding place here or in town and see what they have to offer.  I have done soldering with electronics so I am familiar with the idea, but I don't know what I don't know, if you follow me. 

Flint, thanks for the info.  My brother is a machinist and his explanation was close to yours.  I like the idea of the paste and will look for that.  The shotgun rib may go to a professional thinking about it.

Gunnut- so my HiPower has a barrel that is silver soldered together.  Not to be too ignorant, but do they solder them together before heat treating the barrel? 

So many projects and so little time.

[koginam]

Brownels sells several different types of silver solder it isn't a complected process they include complete instructions with the product. I have used it several times and have had very good results, make sure the parts are clean and use lots of flux.  I have used it on bolt handles and front sights without any adverse effects.

[gunnut69]

I would bet that there is little tempering done to the barrel at all.  Most barrels tend to be fairly soft. There are exceptions of course such as the higher grade match barrels for the 10-22, some of which have the chamber ends surface hardened to resist battering by the bolt slamming against them. The factory tubes are not. Shotgun ribs are usually not silver soldered. Soft solder is easily enough for such an endeavor and the reduced heat a considerable advantage. In fact most Simmons ribs today are glued onto the barrels. They use a special adhesive that stays flexible over time. It won't stand a bluing tank but is easy to re-glue and to remove and since the ribs are aluminum the rib itself wouldn't survive in a bluing tank.

[wtroger]

Brownells & Midway and others sell a soft Silver content solder that has a psi ratiing of 40,000 and melts at about 400-450 degrees F. Now it is not as strong as the high temp solders but for attaching small parts to barrels or actions it works very well. They come as kits with the flux and it is an acid base so be careful. if at all possible I flux and then tin the piece I am going to attach then clean and flux the spot where it is going clamp in place and heat only enough to see the solder flow. The key word in soldering is clean clean and clean again.