Silver solder (hard solder) question

[Dennis Glazener]

I hope someone with experience with high temp silver solder can answer my question. i was letting a custom made trigger guard and had the front extension finished and the rear extension partially finished. I needed the rear extension bent a little for the cast off, I broke off the rear extension! It had been welded but wasn't a full weld evidently (just tacked). I would like to silver solder it back on but would like to leave the old weld there to make it match up as much as possible. If I use high temp silver solder, I have had the roll for years and think its 50-60 percent silver, will it "wick" into the joint like low temp solder? I hope to put a thin coat of white flux between the joints and wire or clamp it in place then "wick" the solder into the joint. Sound reasonable? Thought I would ask before I make a mess with it and have to clean it up!
Dennis

[heinz]

Dennis, I find that high temp silver solder will "wick" very well but the temperature and flux are critical.  The flux I sue id from Brownells and I think is borax based.  I find I have to bring the temperature up slowly and not "burn" the flux.  That is you do not want it to bubble up quickly and oxidize.  I am not familiar with your flux.  When I need wicking I have my best luck with a MAPP torch as you have to get very close to red heat.  You will need a good solid clamping arrangement.  I have never tried it on brass but I used to silver solder copper mugs and coffee pots with great success

[boman]

Dennis, it will wick/flow towards the highest heat.  ie if you place a sliver/piece of solder on top of joint heat it from the bottom.  It won't take very much solder if you have a good tight joint.  melting temp for "easy" flow, which is probably what you have(56% silver) is 1150 give or take iirc.  use a borax-base flux available from a jewelers supply.  I have always used a product called handyflux.   heat slowly as mentioned to avoid "boiling" and it will melt to a glass as it gets red hot and the solder will flow nicely.

Steve

[WadePatton]

Harris white flux is available everywhere and is all you need for the application. grab some 56% non-toxic filler while you are there.  a lot of the old stuff has a toxic component-which is best avoided.  sorry the name escapes me presently.

yes 56% (and up) wicks very nicely.  I don't have the specs handy, but for tubing-it must be an almost snug slip fit.  too loose is no good (bronze loose-the gap needed for brass brazing) and of course there has to be some gap for the silver to fill.

there are variations on silver brazing (this heat range is brazing not soldering) alloys, 45T comes to mind, that don't wick very well.  

warming the flux gently is very important, burned flux is as bad as no flux. when the whiteness goes to gray/glassy, then you can bring the heat and pull the silver where ever it needs to go.

for a big complicated critical joint, it's best to only add filler from one or two points and pull it through to ensure full penetration.

[Dennis Glazener]

I have never tried it on brass but I used to silver solder copper mugs and coffee pots with great success

Thanks to all who responded.
Its steel, not brass, I forgot to mention that.
I got the flux at the same time I got the silver solder so I feel sure its the correct type for it. I am sure it contains borax. The labels are not readable. Its pretty strong stuff, I have used it to join two piece butt plates but on them I was doing it from the inside and I wasn't concerned about appearance. Hoping to have minimal clean-up by just wicking enough to join the two pieces.

Thanks
Dennis

[Mark Elliott]

Dennis,

If it is steel,  why don't you weld it back?   I know you said you had a stick welder.    It will take you seconds with that.    If you solder or braze,  it will show and not in a place it is supposed to be.   If it is brazed at the bow or rear extension,   why not make a new piece and attach it at the existing braze point.   It takes me minutes to forge weld a grip rail and rear extension once the forge is up to temperature.   I will help you fix it without the silver solder if you want.

Mark

[JTR]

Dennis, I agree with Mark. If it's steel, just weld it.
Silver solder will leave a line that won't take the same color as the steel no matter how much you want it to. The only way it won't show is to leave the steel bright.
John

[heinz]

Dennis, i think I understand the aesthetic of the period repair.  You could stick weld it, or you could epoxy it and paint it black.  Mark's offer to forge weld it is interesting because in that process  he could swage the extension about a 1/16 wider and longer so the inlet would go easier.  You might want to consider that stretching option even if you silver solder.  I like the solder line and many originals have it.

[mtgraver]

Dennis, for what it's worth, many of the "period" repairs I've worked around were probably brazed and not silver soldered. I have used all sorts of silver solder because it was given to me and waste not, ya know. A good flux for this repair is Stay Silv I believe is the name. The better the fit the less you can see the joint to almost invisible. That's the trick to soldering silver objects since the silver solder doesn't bridge gaps very well. Either way you go will be a fine job I'm sure.
Best regards,
Mark

[Dennis Glazener]

The guard I used was the "master" that a friend had made for my Gillespie guards. I had sold out of the steel guards and needed one for this rifle. I decided to use the "master" since I didn't need it anymore. My order of steel guards came in Sat and I checked and can use one of them in the existing inlet so I am ok even if the silver solder repair doesn't turn out looking right. I just want to try it and see how it looks.
Thanks for all the info,
Dennis

[Dennis Glazener]

Just finished silver soldering/brazing the extension on the guard and it turned out better than I expected. Since I used this same silver alloy to braze the buttplate together I think this will work fine after I final file/polish it. Right now I can't see the braze line but I am sure after I polish/brown it will show up. I am very pleased with the strength of the joint. When I finished it looked as if it needed to be bent even more than when I broke the weld so before I filed it down I bent it to where I wanted it and the joint held fine. Here is what it looks like after rough filing.

[Habu]

I tend to it hit jobs like that with cold blue a few times during the cleanup.  It lets you see the solder lines.  Most of the time, there isn't much you can do about them but once in a while it will let you shape things to reduce the line or get that "extra bit" of wandering solder. 

[Dennis Glazener]

Oh, I meant to mention that I used a piece of wire to hold the two pieces in place. I had a large spring clamp but I was afraid it would act as a heat sink and keep my little Mapp torch from getting the pieces hot enough to braze. I wrapped the wire around the mid-section and twisted it tight with a pair of pliers. I was very surprised that when I finished the wire had not been brazed to either piece. Actually very little filing with a bastard knife file to get all the surplus braze off.

I tend to it hit jobs like that with cold blue a few times during the cleanup.  It lets you see the solder lines.  Most of the time, there isn't much you can do about them but once in a while it will let you shape things to reduce the line or get that "extra bit" of wandering solder. 

Great tip, will try it.
Dennis

[Dr. Tim-Boone]

Nice work Dennis.  I am going to have to learn how to wire pieces together and get me a MAPP gas torch.  I have some trigger guards that need some repairs...

[Dennis Glazener]

Thanks Tim, as long as the metal is not too large the Mapp torch works well. The problem is larger parts such as a butt plate or something you have to put a big metal clamp on just won't get hot enough for high temp silver solder (1100-1200 degree). What I do on a butt plate is to either use my coal forge or place a single burner Coleman stove under the items to "help" out the Mapp torch. Suspect if you had a second propane or Mapp torch that would work as well.
Dennis

[heinz]

Looks very good.  I hope we get to see pictures when the rifle is done.  Interesting guard

[wmaser]

I use two torches all the time for bigger pieces. works very well with silver solder. Now, brazing with brass I have to go to the forge.