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Solder gap minimum size?


#1

We all know from practical experience that when there is too large
of a gap in the construction of a piece there will be a poor join…
also known as sloppy craftsmanship.

On the other end of the scale, is there a minimum gap necessary for
the solder to wet the surfaces of the pieces to be joined?
Specifically in a case where a tube with a wire inside is drawn
through a plate until the fit is extremely tight, could this gap be
too tight? This of course is somewhat of a special case, I would
think, since the tube would seem to constrain the wire from moving
when heating. I’m curious if there are problems anyone has
experienced concerning a minimal gap… flux flow… solder flow,
etc.

Thanks in advance.

J Collier
Small Scale Metalsmith
http://jlcollier.com


#2

Yes your wire in a drawn tube is likely too tight to get much flow
into the joint. Less than 2 thousandths of an inch clearance is
asking for trouble. Most types of joint are suggested to be in the
3-5 thousandths realm. To be real specific it will depend on a wide
variety of factors, the materials involved their rates of thermal
expansion, the flux used, the cleanliness of the base metals and the
viscosity of the solder when molten.

Jim

James Binnion
James Binnion Metal Arts


#3
Specifically in a case where a tube with a wire inside is drawn
through a plate until the fit is extremely tight, could this gap
be too tight? 

On many occasions I’ve soldered such a setup (although not drawn),
mostly stuff like hinges to secure the axle end cosmetically neat.
I’ve had some freeze(deeper penetration than I wanted) and some
worked just fine and then some others would look good until filing
and then the lack of penetration became clear.

I’d say that at some point, yes the solder will cease to flow
because the cavity is just too narrow.