Ratcoon said:
Hi Dan,
Am I right to say that when the knife is new and in the open position, the liner should be as much to the right as possible and will slowly move left with use (or non-use since the spring is under tension when the knife is in closed position). Finally when the lock becomes really weak, it will not move sufficiently to lock the blade i.e. it will just move a wee bit and still remain on the left.
Thanks very much.
Ratcoon,
You have it exactly backwards. I've never seen the tension on a liner relax sufficiently to see something like what you're describing. If that's the way it worked, I'd think even less of liner locks than I do now, and that's saying something. Tension on the lock leaf isn't the culprit here, it's wear on the lock face.
The liner starts on the left. When you open the knife, the liner pops to the right under tension. The tang of the blade that the liner touches is cut at an angle -- somewhere between 5 degrees and 12 degrees usually. As the liner springs to the right, eventually it's so engaged against the blade tang that it stops ... it is, presumeably, all locked up at this point. Now, every time you open your knife, the liner rubs against the blade tang, and a little more of the liner is worn away each time you open your knife. As the liner wears away it gets shorter, which means that it can spring over
more to the right before it engages the blade tang. Again:
as a liner lock wears, you will see the lock occur more and more towards the opposite scale (on the right for a righty)
Spring tension isn't the driving force here. It's a combination of wear on the face of the liner, and the frame and overall mechanism "settling in". So, when new, a liner lock will lock up relatively closer to where it started. As it wears, it will lock up relatively farther away, towards the far scale. When it's reached the far scale, it's got no more room to wear. If the face of the liner wears any more, it will no longer solidly engage the blade tang, and blade play and an unsafe lock will be the result.
Joe