Dimensions of Copper pipe used in 12v pcp compressor.

If the copper tubing is of 'Nominal' size, it is the inside diameter (ID) that is used (1/2" is the Nominal size that might be used in your home for instance).
If it's a Refrigeration tubing, then the outside diameter (OD) is used.
Either way, they are basically identical with respect to dimensions (1/2" Nominal is 5/8" OD for instance).
Since different wall thickness makes the ID a slightly different dimension, you would likely be better off using the OD measurement.
However, since this is for an air compressor, the wall thickness is very likely 'Type K', which is the thickest of the normal off-the-shelf coper tubing.
Type M = Thin Wall (not made in Soft Copper configuration)
Type L = Medium Wall (made is Soft Copper configuration)
Type K = Thicker Wall (made is Soft Copper configuration)
So, just measure the OD of the tubing and that should put you on the right track.

Mike
 
"For a PCP compressor you shall use stainless steel tubing also the beads and fittings. I don't think a copper tube can survive the pressure."
I fully agree, but there was no mention of pressure in the OP question.
Type K 1/8" can handle up to 3,000PSI at 100°F. 2,600PSI at 150°....and obviously less PSI the higher the temperature rises. Even at those ratings, stainless steel is the best option.

Mike
 
What compressor?

And WHY would you desire to use copper on a high-pressure compressor? Or are you talking about water cooling lines?
Hi man, i have a similar to vevor 12v pcp compressor, but the one i have is different brand name. It's presure lines are made out of copper lines, at least that's the look of it. I just want to keep the spares of those pressure lines in case if there comes a need.
 
Hi man, i have a similar to vevor 12v pcp compressor, but the one i have is different brand name. It's presure lines are made out of copper lines, at least that's the look of it. I just want to keep the spares of those pressure lines in case if there comes a need.
Just buy a spare part. I did that with tuxing. Pre-bent correct lines and fittings.
 
McMaster Carr and Grainger will have the tubing you need. (I’m personally not a Grainger fan).
You need to make sure of the proper wall thickness and PSI rating.
AND make sure you use the proper PSI rating on the swage fittings, The fittings might be a challenge if you aren’t real familiar with the different designs and manufacturers. They most likely will be metric.
You’ll most likely need a tube bender too.