Thursday, June 25, 2015
The Right Amount Of Precision
We often field questions about the accuracy required to install our vises, or the precision required when building a bench. More often than not the assumption is that you need to get your wood perfect down to the last thousandth of an inch. Or something aligned dead on. But the one that makes us smile the most is the one where folks think that vise jaws need to close like two components of the international space station mating up together for the first time in zero gravity.
The truth is, precision can screw things up. When speaking of how vises hold wood, we like accuracy. And what I mean by that is that the vise grabs and holds the wood perfectly every time. What we aren't looking for here is precision. In other words, the jaws of a vise should have some amount of free rotational movement. This accomplishes two thing. It keeps the mechanism moving freely, and it allows the jaw or chop to conform to the shape of the workpiece.
To achieve this, we machine our vises accurately (they all perform consistently), but only build precision where needed. Some of our customers complain that their chop rotates horizontally after installing their vise. They assume the chop is supposed to close perfectly parallel with the front edge of the bench and not rotate, but be stiff, like a Record-style vise. But that precision is a handicap. It restricts movement, and all but guarantees that the vise will work stiffly. Yes, we work mostly with parallel-faced stock, but occasionally we need to hold other shapes too. But if the chop is left free to rotate a bit, it will naturally seat against flat stock and hold it fast, and also hold tapered work.
To illustrate, this week we're building some staked furniture and working some tapered octagonal legs for a small reading desk. The Glide, with its intentional imprecision has been perfect for this. These legs taper from 2-5/8" to 1-5/8" over 28".