Hmm...My border collie was a chewer too...Sometimes I gave her ice cubes to chew on, since she was in a real teething pain. Sometimes it just works to have your dog doing something else or just cheweing something else. If he doesn't chew his own toys, you could try making them taste better with chicken soup or peanut butter.
Border Collies are really smart, and they usually stop chewing after teething. I swear, I thought my dog would never stop chewing and behaving like a devil, and now she is my angel.
Also, Border collies are very, very sensible. You should use your voice tones carefully, a sharp "no" can do wonders. They are also very sensible to being picked by the scruff, I avoid that myself because I know my dogs hates it.
I dunno if I was any help, but those are my two cents. Good luck with your dog