I'd like to offer my humble opinion on this subject. For starters, let's assume the average knife blade is 1/8-inch thick (wide). In thousandths, that comes to .125-inch (one hundred twenty-five one-thousandths of an inch). The average liner spring is .060-inch. some makers state the rear edge of the blade should be beveled about 10 degrees, so when the liner spring swings in its arc, the face of the spring is at the same angle as the rear of the blade. Now, upon opening, as soon as the side of the blade moves away from the liner spring, the spring, under pressure, will pop over behind the blade, locking it in the open position. I feel the spring, all .060-inch of it, should be fully behind the rear of the blade for a complete lockup. Then, as the spring and/or rear of the blade wears with use, the spring will continue to move to the right (looking down on top of the upside down knife) until it contacts the other liner. This means the spring can move a maximum of .065-inch, before it stops, or slightly more than twice its thickness.
Yet, I've seen dozens of custom and factory liner locks where the spring engages no more than .015- to .030-inch of the blade upon opening. I feel this is bad news, because .015-inch is almost paper thin. If the face of the spring and rear of the blade are at the exact same angle, and their faces are sharp, they seem to work, because when the blade is being used, cutting pressure is pushing up on the blade, not down, so it can't close accidently. Anyway, something to think about.
