Greg A
Hi All,

I don't really have the space required to heat metals to melting temperatures, so I'm pretty pumped anytime i get the chance to do any metal working. The other day my boss wanted me to fix her antique fireplace screen for sale on ebay. It's a cast brass frame, pretty neat piece. There was a part where the brass snapped, and I soldered it back together. The spot where it snapped looked like it had some irregularities from casting, that made it weak, and the two ends were torqued where they didn't want to line up perfectly   . I cleaned the two ends with brasso and a steel wire brush, wiped everything clean, fluxed the area, place some solder in between the two ends, then heated it up with the torch. I had the torch directly on the joint, and the solder was complete in about 30 seconds or less. Since the two ends didn't want to line up,I used a steel spring clamp to squeeze them into place. The joint set okay, but I think the clamp sucked all the heat out of the ends, because the solder didn't flow well there. Also, the clamp wasn't strong enough, so it didn't 100% line up. Anyone got any pointers on what I could have done better? Maybe less flux? More gradual heating, or not heating the joint directly? This is one of the first times I've soldered something non-electrical. I'm going to be soldering a brass guard to a 5160 knife blade (one of these days...), so I was happy to get this practice in. I wish I could do cooler things than this, but one day I'll get there.

IMG_1628.JPG 

IMG_1669.JPG  IMG_9028.JPG 
Quote 0 0


Skarzs the Cave Troll
Move the torch around the entire thing to heat it up as evenly as possible, and if you want the solder to flow more uniformly, once it has melted you should brush around the entire area soldered with the flame to draw the solder through and through.
Quote 0 0
jmccustomknives
What kind of solder did you use?  Probably should have used silver instead.  If it's a low temp solder being close to a fire may weaken the joint.  It is a nice screen.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
Greg A
I used silver solder, 98% tin 2% silver. How would using silver work? Would I just take a hunk of raw silver?
The stuff I used is a low temp solder, and I didn't think of the fireplace heat messing it up, which seems obvious. Any chance I can redo that?
Quote 0 0
jmccustomknives
Ideally you'd use a 45% silver alloy, it's stronger than the parent material.  I couldn't find a 98/2 listed, but one close didn't give a tensile strength.  I'm not sure what the best way to redo the braze.  You may just need to let the old flow out and the new will come in.  The stuff you used has a melting point of around 400F, so it may hold together if they don't move it around too much.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
Greg A
Thanks for the information. I'm not sure if we'll redo the braze, since it's already done, but it's good to know what I should have done.

I bought some stay-brite silver solder for soldering a brass guard to a knife blade:

http://www.amazon.com/STA-BRITE-Silver-Solder-STAR2000-Stay-Brite/dp/B0015H6JYS?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o04_s00

Do you think this is still a solid choice for that application? My idea is that the low temp stuff would be better for the knife, and I should of used the 45% silver for the fireplace application.
Quote 0 0
Skarzs the Cave Troll
I know a lot of people like the silver solder for knives since there's less risk of ruining the temper, but I've never used it on steel, so I'm afraid I don't know.
Quote 0 0
jmccustomknives
Generally speaking, the main reason to use the solder on guards is too fill in gaps and not to hold the guard in place.  You should pin it as solder has little strength, one good hit and it could break loose.  I don't use the stuff as the goal is to fit the guards as perfectly, with no gaps as possible.

Rule #10;  "I can make that" translates to; "I'm to cheap to buy it new."

Quote 0 0
Greg A
Then I might not need to solder at all, because I've left myself enough material to press fit it, after some delicate filing. I should get a good grip between the materials. I've got a 3/8 thick piece of brass going on a 1/4" thick blade.

It was still fun to solder that fireplace screen, even if I botched the job, and the tin is going to crap out after a few hundred degrees gets to it. Thanks to everyone for all the advice.
Quote 0 0
Kiwi tussock
I would have brazed it using a bronze stick. Oxy/Acet with a no 2 tip rather than a Map-Gaz bottle with a turbo set up..
Solder will hold for a while and because it look a really nice piece, its probably gonna last for a long time 'cause its unlikely to me moved or kicked around much.
Bronze is very strong but solder just hasn't got the durability in my opinion.
But.... Im a learner in this life, so others with better knowledge might be better to listen to.
Quote 0 0
Scrambler82
To me... there are two problems... the first, not enough heat and solder used and the second, not enough surface area to make a good joint.

What torch are you using ?  I would use an Oxy/Acet Torch with a Rose Bud tip to spread out the heat, as stated above you need to get the heat all around the piece as evenly as possible.

The surface area you are tryin to connect, if just rough ends, is too small to maintain a connection with 
longevity.  You need to add a reenforcement in the back of the piece.  Slightly heat an extra piece of brass and form it slightly to the rear of the frame once you have the piece formed you need to use liquid flux, an acid based flux is the best, and should allow for a quick flow of solder.  Brush the liquid flux on heat it up and watch the flux go somewhat clear then apply the Silver Solder, the good stuff not the 2% stuff.  You will need a solder diameter that will supply enough solder to the heated point to make the joint strong enough. 
When clamping the piece, extra heat needs to be applied to compensate but there is a limit so go slow.

One more thing, I am not sure what the melting point of Cast Brass is... Im thinking higher than the Silver Solder... BUT we don't know the material content, I do know soldering copper and brass pipe is heat until the solder flows then remove heat while still applying the solder.

OK other ideas:
1) What about just making a support, form it to the back of the frame as best possible, clean things up, maybe even use some very small screws and secure the support before solder the front and only the front.  The front is flat so a slight chamfer on the pieces, fill chamfer and then clean up the front.  Keep the chamfer small, and unless the boss want to get away with a broken piece, it should look ok.
2) Make a "U" shaped piece of brass and solder it to the front of the piece, clean, liquid flux.  Add a similar piece to the other side, same place, shouldn't look too bad.  
3) Maybe combine 1 and 2 !

That's all I can add to this topic, thinking too much, Silver Soldering is like Brazing, heat is your friend to a point and sometimes it is better to take it to someone that know the material and how to fix it the best way !


Do It Right The First Time !
GrevB
Location: SoCal, USA
Quote 0 0