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I just had a rear sight installed on my shotgun, and the gunsmith used soft solder . Now I am getting this gun coated with Gun Kote,so I am spending quite a few $$ on it and a guy on another forum told me the soft solder will eventually let go. I have no knowledge of solder. Can anyone tell me how permanant and reliable is this type of soldering ??

Thanks !

CaptainStef1
 

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Cap'n, If it is a good 100% joint you should have no problems. I have soft solderd front and rear sights and never had one come off. Cheers chester.
 

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The secret to a strong soft solder sight job is the fit of the sight to the barrel.

Done right, it'll stay put unless you whack it with a hammer.
 

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As usual, I am coming in late in a conversation ..... I have used soft solder on numbers of firearms over the years. For example, I have cut off a worn front sight on a broomhandle Mauser and soldered a newly fabricated one on the flat that remained. Many of my blackpowder handguns have had newly fabricated sights soldered in place (since they never shoot to point of aim out of the box.)

Some of the better soft solder alloys will have tensile strengths in the 4000 psi. range. Brownells and Midway are good places to look. You can find the same stuff (sometimes) at hardware stores and such (check the specs on the roll or box.) Fit, preparation, and the correct flux are the keys to a good job.

Remember that the surface area of the solder bond will ultimately dictate how strong the end result will be. If you are trying to solder something that only presents a tiny surface area, it may not be a good candidate for a solder repair. As an example, if you try to increase the height of a thin sight blade by soldering a thin extension to the blade, you would likely break it off the first time it gets bumped.

If you like numbers, it's real easy to calculate the theoretical "holding" strength of a solder joint. Just measure and calculate the area of the solder joint (just the one surface.) Then multiply the area (in square inches) times the tensile strength of the solder. This should give you the "pull' that the sight or other part should withstand. Probably, of more importance, is the shear strength of the joint. This would be more representative of a "sideways" knock. A good rule of thumb is to use 60 - 70% of the tensile strength. So if you get 8 ounces for the "holding" power, it isn't a good candidate for solder. Typical dimensions of the bases of most sights will give you many pounds of holding force - plenty, unless you are pulling out fence staples with your front sight!

This is probably more that you ever wanted to know, so I'll shut up.
 

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I don't know if silver solder is soft solder but I've always used silver solder for gun work. Never have anything come loose.
 

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reddog,

Real silver solder is a hard high temperature solder - actually more of a braze. Some manufacturers call their silver containing soft solder "silver solder," which does confuse a lot of folks. Actually, I like the silver bearing soft solders - they usually are some of the stronger soft solders.
 

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Silver "Bearing" SOFT solder is soft solder that contains around 3% silver to strengthen it and to prevent tarnish.
It typically melts around 400 to 600 degrees or so.

Real silver solder is actually silver BRAZE. It melts around 1100 to 1300 degrees and requires a red heat to melt.
This is not good on some hardened gun parts where the high heat will ruin the heat treating.

For sights on shotguns, soft solder DONE RIGHT will usually hold forever.
An old gunsmith once said about soft soldering parts "Yah, ven you can squeeze out nearly all da solder from da joint, DEN it vill hold".

He was referring to getting the parts as closely matched as possible, with the bare minimum gap between parts.
 

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Discussion Starter #8
It was on a break action single shot shotgun I believe the hinge block is soldered at the manufacture with silver solder so I presume this is why my gunsmith used soft solder to not reach the point of melting of the silver solder of the hinge block.

Please let me know if that make sens.

Regards

CaptainStef1
 

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That silver bearing solder is a lot better than the usual non-lead solder for general sheet metal and plumbing. It flows easily at relatively low temperatures and fills joints well, holds better than the cheaper stuff and is well worth the extra cost. You do need the correct flux and perfectly clean surfaces. And any big gaps - or voids - will weaken the joint.

Brownells shows the following info on flow temp/tensile strength:

no lead tin/antimony - 475 deg. 10,000 psi

4% silver 96% tin - 475 deg. 14,000 psi to 28,000 psi (depends on metal joined?)

5% silver 95% cadmium* - 650 deg. 38,000 psi

56% silver braze - 1205 deg. 85,000 psi

* Cadmium is a poison
 

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jjk308,

Thanks for the solder spec. listing from Brownells. Where in the world did I come up with my 4000 psi spec? I must have been thinking about epoxies. I reckon I'm getting a bit senile - all the information is still in my head (I think) but it just sort of gets stirred and shaken at times.
 

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Sounds like a quick set epoxy to me.
 
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