Need silver soldering HELP !

Well, after 35 yrs as a machinist/toolmaker, I figgered I might know a thing or two about metal joinery techniques. HAH !
I have a 4" model 28-2 that's been altered to .44 Special a'la Skeeter. Just love it! However, it still wears its .357 sights, somewhat lower (about .060") than those on a 24 or my 624, causing it to print high. I polished the end of a length of .125" brazing rod hemispherical, to make a Marble-style bead. I have a Tablespoon or so of very fine .999 silver spelter, leftovers from finishing ops on coins & medallions I made on the job. Company position was that the filings were minuscule and not worth the energy to recycle. YAY!
I got some 20 Mule Team Borax for flux, and just to make sure it was gonna work, tinned the end of the bead with silver. Worked great ! I then took a 1/8" round needle file and filed a groove in the front sight .060" deep, figuring to raise the sight the required .060". Cleaned everything w/acetone, applied flux, applied spelter, applied my Bernz-O-Matic MAP-PRO flame, and the flux melted, the silver melted, and steadfastly refused to run on the steel.
Any ideas why she no workie ? MAPP not hot enough? Borax wrong flux for steel (worked swell on the brass)? Any other ideas? HALP !

Larry

The local welding supply has a kit for about $17. Steel to steel.

I would guess that it is maybe both wrong flux and not enough heat. A/C repairmen join copper tubing with no flux, but I have never tried silver soldering steel without flux, and I always use an oxyacetelene torch, because I have to get the steel red hot. The flux I use is a white paste of some sort. Bluing always suffers because of the apparently acidic nature of the flux and the heat required. Brownells sells, or used to, a silver bearing solder that melts at a lower temperature that I have used successfully for attaching sights to gun barrels.

Thanks, 4barrel, I'm trying to do a brass-to-steel joint, and was hoping to avoid the retail establishments, but it may yet come to that.

Larry

Would a lower rear sight slide (some refer to it as a sight blade) solve the problem? It certainly would be easier to install.

I would be interested in more information on that steel to steel soldering kit if you have it 4barrel.

The ONLY times I have been successful in silver soldering brass to steel is by using the low temp. silver solder sold by Brownell's with that same acid paste flux and lots of heat. MAPP 'should' be hot enough, but you have to look at all the surrounding conditions as it is marginal. Look for things like air flow and the steel of the vise wicking away your heat. .......

The filler material that A/C guys use to join copper tubing without flux has phosphorous in it.

(It used to be called silphos)

Sorry, I only know how to braze steel,,,

Maybe it would be best to "wet the steel area with braze, then solder to the braze metal.
That way,,, you do not need to solder directly to steel??

Is the front sight blade/base you are attaching the bead to still attached to the barrel?

If so, remove the blade or the blade/ramp assembly from the bbl as the heat needed to do even a small hard solder job can damage the bbl bluing and possibly the bore if not protected from heat scale.

Second, 'silver solder' maybe the common name for the hard solder process, but silver ( pure @.999 or even sterling or coin grade) is not what you want to use.
Melting any of the above silver grades will require temps from just over 1600F for coin silver to just under 1800F for the .999 Silver you have.
That's way more heat than you want to expose the finished parts to.

Commercially available silver solders (hard solder) for general use can be had that melt and flow in the 900F to 1100F range. They do contain silver,but only a very small %. Their strength comes from the different alloys they are made of in cadium, silver, copper, ect. The list of specialty solders is long. A general use solder is all that's needed.

Even then you can see that at temps of around 1000F, that the bluing will be damaged in any hard-solder job.
Heat scale will form on unprotected surfaces. You don't want that on the interior of the bbl/bore. There are ways to coat the bore or even flood it was inert gas to protect it during the work. But simply removing the small part is much easier both for the work and necessary clean up and re-blue to come.

Simple Borax as a flux works. Dampen it a little to make a paste so it holds onto the surface better and warm the surface up a little to get it to melt and cover the area to be soldered. Commercial flux is always available. A small jar costs little.

Too much heat can burn the flux away and leave the surface unprotected once again from the air and it oxidizes. No solder will stick to it at that point.
Heat slowly, the flux will turn water clear on the surface. The steel underneath the puddle melted flux will be clean looking even as the heat approaches red-heat temp. Using a hardsolder in wire form, touch the surface to see if it will melt the solder on to it in the fluxed area. Don't melt the solder with the torch. If you do pull the solder away and hopefully you will only be left with a small bead of unmelted solder in the puddle of flux. The steel isn't hot enough yet to melt the solder.
Keep gently heating the steel (but not the fluxed area directly with the flame) till the solder suddenly melts and flows accross the fluxed area.
Then take your other part already shaped, cleaned and ready to go and pass it into the flame for a second or two and then touch it into the flux. A coating of flux will instantly adhere to the new surface of the part. Then quickly place it into position in the area where you want it to be where the solder has been melted and has flowed .
Position,,hold make sure the solder has flowed between both surfaces,,then take the heat away. The parts will cool rather quickly to freeze the solder,,you can see it change color and tecture.
Let it cool naturally at that point,,it's still very hot and will take a while. Don't be tempted to cool it down with water, that'll just weaken the joint.

when cool, any hardened flux will be glass like and hard as a rock.
Placing small parts in a tin can on the stove with just boiling water for 10 minutes or so will clear that. Much easier than polishing it off. The stuff actually shatters off in small fragments easier with a hammer or hammer and punch and working over with a file. But hammering on small parts can cause other problems. Better to boil and read the paper for a few minutes.

You could try instead what is now more commonly called 'silver solder'. It is soft solder made of mostly tin with a very small % of silver. It's the greeny replacement for evil lead/tin soft solder.
It is in most cases a bit stronger than lead/tin alloy solder. It melts and flows at just a bit higher temp than good old 50/50 or 60/40 lead/tin but is easily worked with a soldering gun or propane torch. Common paste flux works fine with it though some say a special flux is needed. I've use a lot of both and never had any problems. It works fine on steel, brass, copper. It does stay bright unlike the lead alloy solders that oxidize to a dark grey color after a while. Not a real issue here but it is in some restoration work.
Most home improvement stores sell these tin/silver 'no lead' soft solders now. They aren't something that's special order or hard to get.

Just some info for you,hope it helps..

Thanks, 2152hq, lots of good info there ! So it sounds like the Ag/Sn will be a good candidate. Think it'll stand up to the recoil of a stout Special load?

Larry

I'd try attaching it with one of the tin/silver soft solders. Sounds like you have a reasonably large contact surface betw the blade and new bead. The more contact surface the better of course and the better fit the better. Soft solder of any kind in itself does not have much strength when it's used as a gap filler. But when both joined surfaces are a very close fit, soft solder can take a lot.

One thing you can do in making up the bead is to turn a short peg on the back side of it,,and drill a corresponding hole in the face of the blade to accept it. I know you have the skill being a machinest.
No particular dimensions, just what ever looks strong. It allows more contact when soldering and is an incredibly strong attachment with any soft solder.
I've seen them done that way with a close fit and attached with red loc-tite and never come loose. This method avoids any chance of damaging bluing as no heat at all is applied.

Super Glue?

shawn mccarver said:

Would a lower rear sight slide (some refer to it as a sight blade) solve the problem? It certainly would be easier to install.

Click to expand...

That's what I was thinking!

In this case the low temp silver solder will work fine. Just shell
out a couple bucks and get correct flux. All soldering is 95%
Prep- clean and degrease. Even touching parts after prepped
can cause problems. The only sights that I have found that the
low temp stuff won't work on is on semi auto guns. This includes
pistols, rifles & shotguns that require sights to be soldered to
a recoiling slide or barrel. That stinging sensation between your
eyes won't come from a bee, it will be your bead.!

Try JB Weld

Most silver solder flux used commercially is a fluoride/borax mixture. This is needed to be sufficiently chemically reactive to get thru the oxides formed during the heating of the steel. You might try using some flux from an ER7018 welding rod in place of commercial silver braze flux.