Incomplete solder joint, slipjoint bolster technical request

S

stezann

Well-Known Member
Hallo,
i'm in the build of a swayback and i had issues.
I have soldered (pre-tinning-parts technique) ss bolsters to ss liners, and one of them shows a little black line front/back where the solder didn't run, at the scale side.
I use the "lead pencil barrier" technique to prevent the solder sticking to the rest of the liner and side of the bolster, and I'm pretty sure that when i joined the 2 tinned parts together i might have smeared a bit of graphite in that area by mistake, preventing the complete soldering.
The problem is that i realized my mistake only while profiling the bolster/liner assembly, so i'm somewhat reluctant to redo in the fear of have trouble realigning everything right.
Do you think i should try to just flux the little gap and solder as is?
Thanks

Stefano
 
I never realized that a lead pencil would inhibit the solder but if that is the problem the only way to get solder to stick is you will have to clean the area in some way. When you heat to the point that you can solder the black line the rest will heat to flow, and that piece will be loose again and may move on its own!

Soldering has not been good to me, I can speak more for things that go wrong. So from experience all contaminates have to be cleaned away or no matter how much heat or solder you put to something you will not get a bond!!
 
The graphite of the pencil is a thing that isolate the steel (or brass etc..) from the flux and solder.
I use it to shield the pin (the pin keeps things in place) and the parts i don't want to mess with solder.
My idea is that if i clamp everything i may be able to run another session of flux+solder without taking apart the bolster.
But you are right, and i have to try cleaning very well that little seam, otherwise i'm only repeating my previous mistake!
Matter is i don't know how to clean that tiny seam, right where the bolster ends and starts the rest of the liner, any idea?
 
YYEEESSSSS!!! :) :) :)
It can be done!
I left the piece submerged overnight in alchool, then thoroughly brushed the unsoldered line area with alchool and a toothbrush. Of course the hair of the toothbrush couldn't reach inside the joint, but had created enough velocity of the alchool to remove the remaining impurities from the gap. Then i passed again the pencil in the bolster's shoulder being careful not to get the graphite inside the soldering joint.
I clamped the tip of the bolster upside down in the vise and put 2 spring clamps on the sides, also put the (pencil leaded) pivot pin....fluxed and soldered.
I added just a little bit of solder for security, but wasn't really necessary because the previous solder wicked into the usoldered line, filling it up to the graphite....that's it, a clean soldered joint!! :)
I hope this procedure could help anyone having the same issue i had.

Stefano
 
Congrats - sounds like you did a good job and salvaged a bummer. That's the neat thing, to salvage something.

Ken H>
 
Yes, since the bolster-liner assembly was completely profiled i didn't have room for any misalignment in case i had to take it apart for resoldering, since my worry about it.
Very happy that the surgical went well and the patient woke up in one piece, without ugly scars ;)
 
Glad it worked out for you! Contaminates what ever they may be are usually the source of bad solder joints clean, clean again and flux.

I discovered that reusing the same brush over and over to apply paste flux, was a lot of my problem, when soldering. I couldn't find the brush I normally used and put a new one into service. All of the sudden the solder was flowing as it should. So tried an experiment and unsure what contaminates were being introduced by the brush but the more it was used the worse my soldering got! Brushes are cheap so quit using the same brush!
 
I must get me a soldering brush!!! are they plastic? up today i used a variety of items from toothpicks to curled pieces of paper tissue.
I use liquid flux, and if i'm not quick the paper tissue starts becoming jelly. I'm very proud starting to get a grasp of the soldering technique eh eh :) And you are right, clean, clean and then clean again...a pair of nitrile gloves helps a lot too.
 
Here is what I use. They can be used for paste or liquid flux. However like I said they pick up debris once used and storage and where you lay it down at must be a consideration.

http://www.mscdirect.com/product/de...003=7867724&src=pla&cid=PLA-Google-PLA+-+Test


8207171-23.jpg
 
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