Plumbers remove that edge with a linoleum knife.
But, a Swiss army knife will do the trick.

On big jobs, I used a reamer chucked into a drill.

Use the hard metal Ts to tap threads into the soft copper pipe.
A little cutting oil will help a lot.
Once you have made and cleaned the threads the tape will work right.

Aloha,
Weeze
Weezard Reviewed by Weezard on . LED-WATER-HEATSINK Hello! I am a noob DIY-LED-GUY, in need of assistance. Now, I'm about to fire up an LED-DIY grow and since this is my first time ever making an LED-LAMP I've decided to jump straight into the deep end of the pool and do a water-cooled rig. As pipes are mostly round there was an issue with lack of flat space to mount the LEDs on and the right parts was hard to find, so it kind of just ended up like it is. My question is: will it work? I have an aquarium pump that goes between the Rating: 5