AB Coltellerie

Help Desk: How does the front opening mechanism work?

The button is not really a button, but rather a slide bar with about 1/2" of travel. Logically when you slide forward the knife opens, and backwards vice versa. When you do this you notice that it takes some force to make the movement, and the further you move the more resistance - just like tensioning a spring. At the end of the stroke, the blade moves suddenly in one direction or the other and all the resistance goes away. This has a tendency to make you operate the slide bar with a "snapping" motion.

Now what happens inside is complicated in terms of timing and ingenuity, but simple in terms of the number of moving parts. There is one (not two) spiral spring, actually a coil spring like on a old fashioned screen door. When you move the slide bar you pull the spring which is then attached to one end of the blade. You are applying pressure which wants to move the blade, but can't since it is locked. When you have applied all the need force (near the end of the travel) several things happen very rapidly.

1. The blade is unlocked
2. The blade moves a short distance under spring tension - but mostly operates under inertia
3. The blade reaches the end of its travel, which locks it again and attaches the spring to the opposite end for the reverse process.

Now how do they do all this? The spring has a hook on each end, which catches over the heel of the blade or in a little recess near the heel. The mere position of the blade determines which hook is in use. The spring runs parallel to the blade in a little metal tray with a protrusion at each end. There are two leaf springs, one to lock open, one to lock closed, at opposite ends of the knife. One of these is under no tension, the other is tensioned and holding the blade. When you push the slide bar, at the last instant, the appropriate protrusion "opens" the tensioned lock. When the blade completes its travel, it tensions and locks the other spring.

The exact function of the leaf springs varies a little from design to design, cheap Mexican versions use a simple flat piece of steel - very flimsy and easily damaged. Others use a true "pivoting lever" affair, like on a traditional side opener - this is desirable.

Final comment, most of these knives are put together with a press fit. You can usually pull off the plastic button, then the scale, and still work the mechanism. I still do this occasionally because the design is so cool. This doesn't seem to harm the knife. and in a few seconds it can be reassembled anyway.

Thanks to Dave