Deburring copper pipe or any metal pipe is important, as the burr can cause turbulence in the pipe, resulting in erosion of the pipe wall. External pipe burrs also need removing, especially if using push fit fittings, as the O rings can be damaged, if burrs are present.

Links to items used in video (I’m not on commission) -
https://www.bmstores.co.uk/products/d...
Deburring tools on eBay- https://bit.ly/3HEAKeI