Liner Lock - where should the liner be?

[Ratcoon]

Hi

In a liner lock with the knife open, where should the liner be positioned with respect to the thickness of the blade. Should it be at the extreme side (on the side that the liner moves to in the knife closed position) or should it be more towards the centre of the blade (thickness) or in the middle of the blade.

Thanks very much

 

[Joe Talmadge]

There's no one place where the liner should be; liner locks are specifically designed to move as they wear. People have their preferences, but I haven't found that a liner that's more to the left is necessarily more susceptible to accidental disengagement than a liner that's more to the right; in fact, sometimes the reverse is true. The only thing you don't want is for the liner to start off so far to the left that it's hanging off the edge of the blade; if that's the case, a few solid openings should wear it in quickly.

The liner should start off relatively more to the left (but not hanging off the edge of the tang), and as the liner wears, it will slowly move to the right. That's the reason you'd rather have your liner start more to the left -- the more towards the center or right that it starts, the less life it has. Once the liner makes it all the way to the right, where it's touching the far handle scale, your lock is "worn out" -- any more wear, and the lock will start developing blade play. At this point, some makers will put in a bigger stop pin or let you adjust a variable-sized stop pin, and that will move the liner back to the left again and give it a new life.

Joe

 

[Ratcoon]

Hi Joe,

Thanks very much for your answer, I may have misunderstood how the liner lock works. Looking down at the liner lock in the engaged position with the knife opened, my liner is on the left. If my knife is new, wouldn't the liner move more to the right i.e. the spring would be stronger when new. With use the spring will become weaker and therefor not open so much and stick more to the left. I seem to have the sides opposite. Please excuse my lack of understanding.

 

[Daniel Koster]

If I am looking down at a right-handed liner-lock with the edge up, the liner that locks is on the left.

When it's open, the spring is not under tension....ie. in action. That is its resting position. When the blade is closed, the spring is now under tension and is to the left of the blade (same viewing position).

Since knives spend most of their time closed (spring under tension) the locking liner will have a tendency to weaken and not return fully to its initial resting position. Which would mean, in short, a tendency to move left.

But all of this is a moot point, if your pivot is loose, or if the tang is not ground right, matched, etc.


And it has little to do with liner strength. Quality of construction is more important, IMHO.

To answer your question, though....the liner should rest "fully" on the blade (like Joe said). Doesn't matter left or right (as long as the tang is squared off).

This is, of course, the weak point of the liner lock. Brilliant design, but not perfect. Frame lock improved on it.

 

[GarageBoy]

Why does the bigger stop pin reset?

 

[Ratcoon]

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.

 

[Joe Talmadge]

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

 

[Ookpik]

Why does the bigger stop pin reset?

There are a few factors in linerlock wear. There is wear of the liner contact surface, wear of the blade tang, wear of the blade stop pin, wear of the part of the blade that contacts the blade stop pin, and wear of the pivot. The two significant wear points are the contact surface of the liner, and the blade stop pin. Putting in a larger blade stop pin would correct the wear of this part. It would also prevent the blade from opening as far, which would compensate for wear of the liner contact surface. It might affect the geometry of the locking surfaces, so you may have to file the end of the liner. You could also peen the liner, near the locking surface, to restore the liner to its original length. The liner would need to be filed after peening.

 

[Joe Talmadge]

Yep, that's an important point. Liner locks are extremely sensitive to the liner/tang geometry. Putting on a bigger stop pin changes that. As a result, not all makers will do this.

 

[Ratcoon]

Hi Joe and All,

Thanks very much for the explaination. I understand it now.

 

[biogon]

As you open and close a linerlock a couple of times in a row, you can see a black powder develop on the cut tang.

I always assumed this was titanium dust from the lockface, given that it's a lot softer than hardened steel.

True?

If so, why is it that all linerlocks don't wear out (i.e. lock up all the way to the right) after a year or so of regular use, like certain unnamed brands?

-j