Deburring copper tubing (often called reaming) is the practice of running a blade around the inside of tubing after you cut it to remove the burr edge from the inside.
It’s an important practice and should be performed whenever practical to reduce turbulence inside the lines that can be caused by the burr…. HOWEVER
YOU MUST MAKE SURE THE SHAVINGS DON’T FALL INTO THE LINE
Whenever possible point the open end downward while you run the blade around the inner edge and then tap the line to ensure that the shavings fall out of the line rather than in. In some situations during repairs it may make sense to purge nitrogen out the line you are deburring especially in repair situations like replacing a compressor where making the lines point downward may be impossible.
If you are given the choice where you must choose between deburring and possibly dropping shavings into the system I would rather you didn’t deburr.
In the case of making flare connections deburring is critical. For a flared tube it is also critical that you don’t over ream the tube and thin out the copper edge otherwise it will be prone to cracking.
Deburring is important, but keeping shavings out of the system is even more important.