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THE HOLE TOOL (HOLE GAUGE)

Hole tool (hole gauge) in brass

What is the hole tool (hole gauge)?

The Hole tool (hole gauge) comes in the form of a plate or small block, drilled with a series of holes of different diameters, designed to receive and hold vertically the components fitted with an Axis or a pivot. Its primary function is to ensure the seating of the component: the part rests flat on its plate, its disc or its body, while the pivot or Axis passes through the corresponding hole and remains free from any parasitic contact. Wheel of the Train (wheel train), Balance, Pallets (lever), etc.: any element of the mechanism whose stability depends on an Axis finds on the Hole tool (hole gauge) a precise, free seating, accessible to the eye, allowing various operations to be carried out on it.

Construction and Materials

Depending on usage, the hole tool (hole gauge) is made of steel, brass or glass (crystal). Steel, generally softened and polished on the surface, offers the best rigidity and the best resistance to wear; it is particularly suited to operations involving slight pressure or repeated support and can be considered as an anvil. Brass, being softer, has the advantage of not marking the fitted components, and remains widely used for delicate finishing or handling operations. Glass (crystal), for its part, offers valuable transparency.

Whatever the material, the plate is small in size — a few centimetres in diameter or width for common models — and thin, just enough to ensure the stability of the component and allow the pivot to pass through without contact between it and the surface of the bench.

Geometry of the holes

The holes are arranged in a regular grid, in a circle or in rows, and their diameters cover the full range of components to be accommodated: from the finest Balance Axis to Barrel arbors. The upper edges are most often slightly chamfered, which facilitates the insertion of pivots and limits any friction detrimental to the edge of the jewel or to the shoulder. On the most carefully made tools, the holes are calibrated with a Reamer and their entries Polished, so that no Burr risks damaging pivots and tigerons when placing or removing the component. The distribution of diameters generally follows a regular progression.

Uses according to components

The Hole tool (hole gauge) is used for nearly all the moving elements of the mechanism. The wheels of the Train (wheel train) are placed on it by one of their tigerons, with the plate resting flat on the surface: the Horologist (watchmaker) can then freely examine the teeth, check the flatness of the wheel, work on a spoke, or simply set the piece down while waiting for Assembly without risking it tipping over on its fragile pivots.

The Balance finds in the Hole tool (hole gauge) a support of choice: placed on its Axis, it allows the Horologist (watchmaker) to inspect the Hairspring (balance spring) or perform an adjustment without stressing the Blade. This setup is particularly useful for cleaning, Testing, or thickness adjustment operations.