For soldering copper pipe/tubing in the 1/2" to 1" range, what is the
proper size gap between the ID of the fitting and the OD of the
pipe/tubing? For example, the ID of 3/4" type L pipe is 0.785", while
the OD of 3/4" type L tube is 0.750"; would this be an acceptable
solder joint, or is 0.035" too big?
I don't understand your question. It sounds like you're asking if the
fittings fit. I've never noticed any appreciable difference between
fittings or pipe sizes. They all seem to fit and I've never had a
problem sweating the joints.
Never put a micrometer on a fitting, though. Why are you asking?
Ah. I think you have confused copper pipe and tube used for
general plumbing apps with the "refrigeration tubing" used
on things like A/C systems. In the latter case, tubing is
always speced by the tube O.D. And there are special fittings
designed to accept those dimensions.
Actually, I was just wondering if a piece of 3/4" type L copper pipe
would work as a coupling for 3/4" tubing. [Or as a bushing in a 3/4"
pipe fitting to accept 3/4" tubing.] But the diameter difference is
0.035", which is apparently too much.
.........The capillary space between tube and fitting is approximately
0.004". Solder metal fills this gap by capillary action. This spacing
is critical for the solder metal to flow into the gap and form a strong
joint. Copper is a relatively soft metal. If too much material is
removed from the tube end or fitting cup, a loose fit may result in a
That would translate to ~.008 diameter difference between parts' ID &
Which is right in the middle of previous post of .003 to .005.
The capillary action is why one can solder a joint where the open edge
Short answer .035 is WAY to big a gap for a reliable joint.
My suggestion is get the correct fitting.
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