Hi Rob!
Hope you had a great Christmas.
Here's an explanation of how various vise designs hold hooks - it's from an article by Hans Weilenmann & Bruce Salzburg, and can be found
here.
Jaw Types
There are essentially two types of jaws used in vises today: collet and lever-type (also called parallel clamp).
Collet vises employ one-piece jaws, which are in the open position, like a pair of tweezers. The jaws are closed by either pulling or pushing them into a ring, called a collet. This is generally accomplished by a lever and cam located at the rear of the vise barrel.
Most collet vises are "draw collet," meaning that the jaws are pulled into the collet. Examples include the venerable Thompsons to the more sophisticated HMH entries. DynaKing's line uses a forcing cone-collet design--or "push collet." The Renzetti Presentation 3000 and the Tiemco vises also use a push-collet design, but with these vises the jaws are closed and opened by turning a large knob located at the back of the jaws. Because of the great force exerted onto the collet, push-collet vises tend to have a substantial metal collar behind the jaws some tiers may find reduces access to small hooks. Draw-collet designs generally have a sleeker profile.
Lever-type jaws such as those found on Regal vises operate like a wooden clothespin, requiring two-piece jaws, a fulcrum, and a mechanism to close the jaws. On some designs, a small screw near the tip of the jaws provides adjustment between hook-wire diameters. Some tiers find that this screw interferes, especially when tying on very small hooks. Either a thumbscrew or a cam lever is used to close the jaws by separating the "tails" of the jaws.
