Para-Military compression lock all the way over... how bad is this?

[Macchina]

I am interested in trading for a Spyderco Para-Military. I have only used a compression lock a few times, and I'm not very familiar with it. The knife is a user and the compression lock is all the way against the G-10 when open. The knife has no blade play. Can I expect some blade play to form after use, or does the compression lock not behave like a standard liner lock?

 

[carrot]

The Compression lock adjusts for wear similarly to a liner lock but once it hits its sweet spot it stays there for a very, very long time, similar to that of the radiused tang linerlock Military.

 

[yablanowitz]

If the lock is currently all the way across, it will have vertical play in the future if it doesn't already. How soon that happens will depend on how you treat the knife. If you do a lot of hard inertial openings, chopping or spine-whacking, it may happen tomorrow.

The good news is, it can be refurbished to correct the problem. I did so to a Yojimbo that was severely beat and had considerable vertical play.

 

[Macchina]

This is not in a sweetspot (I know what you mean by the Military, and I agree), the bar has completely crossed the width of the blade and is now touching the G10 on the other side. Is this normal for compression locks, or should I shy away from this knife because it will soon develop blade play?

How did you refurbish it? Taking it apart and bending the lock bar so that it is more strait?

 

[yablanowitz]

The Yojimbo I refurbed required quite a bit of sheetmetal work to restore it. The stop pin had to be deburred and rotated, the holes in the liners where it fit had to be reshaped, the edges of the lockbar had to be deburred and peened back into shape and a few other things. It's hard to say what would be needed without taking it apart. If you aren't prepared and equipped to do that sort of work, pass on the knife.

 

[storyville]

The short answer is: NO, you don't have to worry about your compression lock moving all the way over.

However, unlike on a 'Walker' or liner lock, blade play in a compression lock folder is not related to the movement of the lock bar. Looking from above or below, both lock types similarly move east-west to open-close; but that is where the similarity ends. On an open liner lock, the blade exerts pressure north-south along the entire length of the lock bar, and blade play can develop as the lock bar becomes fatigued from use.

A compression lock works differently and is much stronger and more fail-proof. Looking at your P-Mil from the side, the open lock bar is pinched or "compressed" between the stop pin and the rear of the blade tang, not along the spring bar. Unlike on a liner lock, no amount of pressure on the blade can cause the lock to fail; the blade would break before the stop pin or pivot pin could be sheared off. Hence, it does not matter where the lock bar stops along its east-west axis because use does not fatigue the spring bar per se. If/when blade play develops, it does so usually because the softer steel sleeve of the stop pin becomes imperceptibly 'compressed.' This is why users often say that they just rotate the stop pin and their blade play goes away.

Also, on a liner lock, blade play indicates fatigue that can affect the performance and reliability of the lock. However, blade play on a compression lock may reflect slight imprecision in manufacturing, but it has no bearing on its strength. Once the lock bar is in place, it can only be closed manually, not by pressure on the blade.

Of course, if you want a response from Spyderco itself, you can post in their forum here...

Hope this clarifies --

Glen

 

[yablanowitz]

I agree and disagree. The compression lock is in no danger of failing to hold the blade open just because it travels all the way across, but when it is worn to that point, it will allow vertical play, even though it still holds the blade open reliably. On the Yojimbo I referred to, the locking tab had been peened top and bottom (my guess would be spine whacking rather than inertial openings, although from the groove in the blade and flat on the stop pin, it had its share of those as well) and was definitely contributing to the vertical play. Of course, on that one the stop pin holes in the liners had been hammered into oblongs as well, so merely rotating the stop pin would not eliminate the play. It took me a couple of hours of careful work to return that Yojimbo to what I consider proper lock-up for a compression lock, and I've done more that a little metalwork over the years.

 

[hardheart]

to reiterate again, one more time - once the bar has moved all the way over, there is no other way to compensate for wear, play will develop.

 

[SIFU1A]

one of my Ti ATR's goes all the way across but it still locks fine, might have just a smidgen of verticle play but not nearly enough to worry about, i mean VERY little, its been like that for ~ 3yrs now its the ATR i carry occasionally and i still inertia it all the time, imho its not like when a liner lock goes across, the LL and compression are different in that regard.