Excelsior key
The Excelsior key is a type of adjustment key for loosening and tightening screw connections. It is both structurally and historically an intermediate solution between the Englishman , with whom he shares the jaw arrangement, but which is adjusted via a threaded spindle, and the adjustable wrench , which, like the Excelsior wrench, has a worm gear for adjusting the wrench size.
Excelsior keys are often equipped with a quick adjustment by unlocking the adjusting screw, but there are also designs with non-unlockable adjusting screw. The advantage over the adjustable wrench is the stable support of the movable jaw, which can absorb a high torque as it completely encloses the handle part. A disadvantage, however, is the lateral arrangement of the wrench jaw in cramped conditions.
handling
As with all adjustment keys, improper handling of the Excelsior key often leads to increased wear or deformation of the tool. If an Excelsior wrench of the type shown in the picture is to be used to loosen or tighten screws or nuts, make sure that the moving part of the jaw or fork always points in the direction of the rotary movement to be performed. Otherwise, the movable side of the fork or the adjustment mechanism can permanently deform and, as a result, have increased play or even become unusable.
While the key is already on the workpiece, the adjustment mechanism is readjusted by retightening the worm. In this way, the closest possible fit is achieved. If the fork width is not chosen narrow enough, this can lead to sliding off the polygon. On the one hand, the screw or nut can give way permanently due to the inadmissibly high edge pressure and thus be "turned round"; loosening or tightening becomes more and more difficult. On the other hand, when slipping, especially when using high physical strength, the risk of injury is great and the tool itself is exposed to too great a load.
An adjustable wrench that cannot be kept under tension like pliers during use or that automatically retighten, should only be used to counter-hold and not to force screws or nuts, as a really tight fit cannot be achieved here.
