THE BLADE CASE OPENER
What is a case opener in watchmaking?
The blade case opener, or Horologist (watchmaker) knife, refers to the simplest of case opening instruments. It is intended for cases with a snap-fit Case back, whose press-fit closure relies on the sealed engagement of a peripheral lip in a Groove of the Case middle. The action consists of inserting the tip of the Blade into this groove, then applying a slight lever motion to disengage the Case back and open access to the Movement.
The instrument consists of a flat Blade made of Inoxidisable (stainless) Steel, mounted on a handle. The Blade is deliberately thick and rigid, with a solid back, and its edge is not sharpened: it is a rounded or slightly bevelled, polished edge, whose function is not to cut, but to engage cleanly into the Groove of the Case back without marking it. Several profiles coexist depending on the shape and depth of the groove to be released.
The operation is performed with the watch held in one hand, the case resting on a soft support or a service cushion, the Blade placed flat on the Case middle then engaged by a moderate rotation of the wrist until the Case back lifts. The most common mistake is the Blade slipping on the side of the Case middle, which leaves a fine mark.
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