Everytime I buy a new opinel I disassemble it, sand the inside expand with the outside of some needle nose pliers both the locking ring and the inside ring and oil the inside. Now I can flick it open one hand, lock and unlock with one thumb and I love it.
And when it ages and becomes too sloppy ? I am ready to tell you that I simply compress the inside ring and take the chance to put two teflon or brass washers inside. Just fiddle with the tension until you get exactly what you want.
I am a diy enthusiast and this part of the brand it's one of the things I love !
A video of a new number 8 I got. If you wish to do the same always remember to keep the tension on the higher limit (as you see in the video) since otherwise it comes loose too fast. In a couple of months it will be perfect and keep that perfection for a year or two, based on my use and the condition I keep my knives.
If you are wondering, no blade broke on me after doing this ! I flick it open just when I have a busy hand and control the force of my flick! Maybe it's a risk, but I say skill issue. Gotta admit that the Opinels I modified like this no one has more than 5 years and the older is a number 12 I use just on barbecue days