Copper plumbing fittings

Hello,
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?
Thanks, Wayne
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Wayne Whitney wrote:

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?
R
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Looks like he's thinking of putting 3/4" soft copper tube into 3/4" L. Normal fitting clearance is .003-.005" as I recall...
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Yes, exactly.

Is that a 0.003" difference in diameter or radius? In either event, a 0.035" difference in diameter is way too much, I imagine. What are the limits for a solder joint?
Thanks, Wayne
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Wayne Whitney wrote:

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.
plumbing sizes: http://www.copper.org/applications/plumbing/techref/cth/tables/cth_table2b.htm
Refrig sizes: http://www.rparts.com/Catalog/Installation_Components/fittings/copper_t&f.asp
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If its copper pipe made to be soldered, a 3/4 pipe fits a 3/4 elbow, male adaptor, coupling etc. If it's copper tubing, then 1/4 inch tubing fits a 1/4 inch compression fitting.
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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.
Thanks, Wayne
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Most of the sweat copper I've done, the pieces touched all around when I pushed them together. Snug fit, too.
I remember o35, cause I used to gap Chrysler plugs that spec. WAAAAY too much slop.
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Christopher A. Young
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Swage it until it fits.
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Oscar_Lives wrote:

.........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 poor joint............
That would translate to ~.008 diameter difference between parts' ID & OD.
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 faces downwards.
Long answer.......
Short answer .035 is WAY to big a gap for a reliable joint.
My suggestion is get the correct fitting.
cheers Bob
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