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Presently: Bevelling and finishes in top-of-the-range watchmaking (III)

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The author

Having acquired an educational background in economics and literature, Caroline Sermier fell in love with watchmaking right from her arrival at Renaud & Papi.
Her current responsibilities as head of the communication department allows her to blend a taste for writing with her fascination for complicated watches, and particularly for the finishing and decorative details on top-of-the-range luxury watches.

14. Bevelling and finishes in top-of-the-range watchmaking (III): methodology

 

High-end bevelling : methodology

Bevelling is undoubtedly the most significant determining factor in aesthetic terms : this extremely meticulous finish highlights the authenticity of hand craftsmanship.
Bevelling is a rare and delicate art which consists in making a polished bevel or chamfer on various parts, the rim of which is underscored by the light playing over the bevels. There are two possible approaches :
1) the modern method (machine bevelling)
2)
the high-end method

1) The modern method : there are currently various modern methods for bevelling parts :
* The bevel or chamfer is made by machining and the polish is then achieved chemically, mechanically or by hand with brushes.

Note : This method is satisfactory ; one can obtain a regular, clean-cut bevel, but the angles are rounded because sharp angles cannot be made by machine (due to the diameter of the milling-cutters).
* For large series, the bevel or chamfer is made and polished directly by stamping.

Note : It is impossible to polish sharp angles with a brush or mechanically. This method is satisfactory but all parts are strictly identical, as it does not enable any degree of personalisation.
The time spent on each part is considerably reduced, implying higher profitability, and the method does not require any particular know-how.

2) The high-end method, on the other hand, requires exceptional dexterity and know-how.
Bevellers are rare, as there is no special apprenticeship for the profession, even if certain notions of the craft are taught in watchmaking school. To compensate for this lack, high-end watch brands concerned with achieving the finest possible aesthetic results (see conclusion) train their bevellers themselves.
Hand-bevelling is a meticulous operation requiring a lot of time ; some parts may require up to 10 hours of work, resulting in high costs that are inevitably passed on to the final products.
For all these reasons, certain companies choose the far less expensive machine-bevelling option.
There are currently two high-end methods :
the burnisher and the wooden grinding-wheel.

a) The burnisher method :
Preparation :
First of all, any residues or traces of machining are removed from the flank. The latter is then smoothed by graining, as good bevelling depends on the quality of the flank ; the aim is to give it a smooth appearance. The surface must be clean with no waves or imperfect shapes.
To facilitate the work of the beveller, the bevel may be blanked by hand (with a milling-cutter) ; but the interior angles are hollowed using a file, as no mechanical operation is capable of making them sharp. (due to the radius of the milling-cutter).
The chamfer is then touched up by hand (*1) ; the regularity of the width of the bevel is essential ; the edges of the angle must remain parallel from one end to the other.

Polishing : While taking care not to create any twisting, the perpendicular marks of the file are eliminated by straight graining and the surface is then smoothed with a stone cut according to the part.
Finally, increasingly fine abrasives (buffs) are used to unify the lines, while taking care to avoid excessive rounding of the edges and the angles* (2).
Note : irregularity and twisting are not in themselves tolerated, except if they make the overall aesthetics more consistent.

At this stage, it is important that the part be extremely clean, free from any residual abrasives which might scratch the surface during the burnishing. This operation consists of cold-working the material with a tempered steel tool in order to create a polish * (3).
Last of all, the polishing is fine-tuned and the final radiance is given by rubbing with a diamond paste using a wooden peg * (4).
This traditional method is the classical method par excellence ; it involves no limits and no constraints.

b)wooden grinding-wheel method* (5) 
: In this case, the preparation is the same, but the polishing is done directly on a wooden grinding-wheel filled with diamantine.
This technique has the advantage of being faster and offering a high-quality result, but it calls for great mastery, as contrary to the burnisher technique, a large quantity of matter is removed and it is hard to make up for a mistake.
The disadvantage of this procedure is that the inside cut-outs cannot be reached. In this case, one will tend to choose the burnisher method in order to achieve better overall aesthetic consistency.

Conclusion :

Machine bevelling is productive and gives a clean, neat and relatively satisfactory appearance ; however, one considers that an object should distinguish itself by the care devoted to finishing the smallest details, true craftsmanship bevelling appears the obvious choice.
The “imperfections” of bevelling are tokens of hand-made authenticity and depend on the know-how of the craftsman, implying that each part is unique and personalised.


See: Bevelling and finishes...(II)

 





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