I think this is the third time I've posted it:
From Sal Glesser on the Spyderco forum:
Hi Poodle,
We've gotten to the point where we can make most locks as strong as we plan for. The Lockback as seen on the Chinook (Manix & 83mm), the ball bearing, Compression and the new Stop-lock can be built into the Very Heavy Duty (MBC - 200 inch/lbs per inch of blade length) range. We select materials and dimentions to meet the requirement we sedt for the model.
We've not been able to get Walker linerlocks or "framelocks" into that range due to the long spring.......yet. But we're still developing.
I think most locks can be made to be strong and reliable if the manufacturer extends the effort.
sal
http://spyderco.com/forums/showthread.php?t=24676
For transparency, that was posted in 06, and to date we still don't have any liner/framelocks that meet that rating. Lockbacks, compression locks, ball locks, yes, liner/framelocks, no.
Given the above, there are two theories:
1) Sal is incompetent. A man who has spent over 25 years in the knifemaking industry, has developed several new locks, and has designed many of them (and the lockback) to fall into their highest strength class. He has failed to do so with the liner/framelock. Incompetent? I doubt it.
2) Liner/framelocks have an inherent weakness, which Sal has also mentioned. Mechanically, it is a true statement. I have also offered this before, and the offer still stands, if you want, I can produce a qualitative mechanical analysis on why a lockback will, in the end, be stronger than a liner/framelock.
BTW, why use a liner/framelock?
1) They're good enough. Frankly, if something fails under 300 pounds of stress, I think you're going to be in much worse shape than the knife.
2) It's easier to put together. John, correct me if I'm wrong on this, but the number of surfaces that have to be mated and aligned correctly on a lockback is much greater than that on a liner/framelock. Quicker to produce.
3) Less parts, therefore cheaper to produce.
None of which apply to which is stronger.
BTW, +1 on AcridSaint noting how you're constantly having to qualify things and switching POV.