Bevelling, engine-turning, circular graining and mirror polishing are just some of the terms that we hear about in the watch industry every day, and each technique is an art in its own right. Not only are there dozens of different ways to finish and decorate a movement’s components, but there are also different grades of finishing that go from one hundred per cent industrial finishing to pure hand craftsmanship. To an untrained eye it can be difficult to tell difference, and for those who aren’t aware of the distinction, the price of high-end timepieces can be totally incomprehensible.
At Jaeger-LeCoultre, for example, it takes two complete days for one highly-trained artisan to hand polish their gyrotourbillon cage that weighs less than one gram; at Breguet each and every dial is decorated with hand guilloche using traditional engine-turning machines that date from the last century; and at Renaud & Papi (part of Audemars Piguet) it has taken them over ten years to teach themselves certain historical decorating techniques that had completely died away. We visited all of the above watchmakers and spent time with their finishing artisans to learn about the staggering amount of work that goes into decorating their movement components and what makes them so special.
The beauty of bevelling
When a component is milled by a CNC machine or by electro-erosion, there are rough parts and burrs that need to be eliminated. It is possible to remove them chemically, mechanically or with brushes, but the best result is most often by hand. “We don’t do everything by hand for marketing purposes, we do things by hand if it is the best way,” shares Giulio Papi, Co-Founder of Renaud & Papi. “If we find a modern method that gives better results, we will use that,” he continues. Today, the best way to finish the majority of movement components is to do it by hand.
Bevelling methods and tools
Bevelling is the process of filing the edge of a component, between the top surface and the sides (also referred to as flanks), to an angle of 45 degrees, creating a chamfer (or bevel). This process removes the burrs and roughness after the machining process, which could be detrimental to the smooth running of the movement. A beautifully bevelled piece improves the beauty of the component itself by highlighting the rim and also helps to reflect the light inside the movement and reduce corrosion.
The bevelling methods that are used today are industrial, stamping and by hand. The industrial method is achieved using a CNC machine and is perfect for series production. The angles are clean, but the machines cannot reach interior angles that need to be finished by hand. Stamping is a process that has been carried out for over three centuries, whereby a press will stamp out the components. The bevels can also be created using this method. The results are excellent, no particular experience is required, but there is no artistic touch to the finished piece. Hand bevelling is a time consuming technique that takes at least a year to learn. There are no schools that teach bevelling and watch companies do most of their training in-house.
Bevels can be created entirely by hand with buffs, files and wooden sticks, or with the aid of a polishing lathe. Both demand extreme dexterity, especially when working with the polishing lathe that can remove the material very fast. It is important for the beveller to finish each component to perfection, without deforming the piece technically.
The perfect angle
In addition to creating the chamfer, the beveller will perfect the interior, exterior and rounded angles – the most difficult being the interior angles where there is often limited space to manoeuvre tools. The exterior angles are where the two chamfers meet at the corner and a rounded angle is smoothed over at the angle of the chamfer, which is the easiest type of chamfer to achieve. Beautiful chamfers and angles, on a bridge for example, can take from 30 to 45 minutes to create, but they give the final piece a more refined and dynamic appearance.
Faultless flanks
In a high-end movement the flanks of each component will also be finished to perfection. It is important that they are completely level and regular. Different types of files will be used to smooth down the surface and remove any imperfections. Filing can leave scratches on the flank so it is often satin-brushed afterwards using a fine pumice stone, buff, scraper, diamond grinding wheel or a synthetic stone attached to a small motor. The effect is hundreds of tiny lines all in the same direction.
Holes and sinks
There are numerous drilled holes, sinks, recesses, bosses and settings in a movement and it is essential to remove any burrs or residual metal for the good functioning of the movement. A perfectly finished and polished sink, for example, can reflect the light around a synthetic ruby, improving its beauty and allowing the watchmaker to better see whether the right quantity of oil is present.
The wonder of wheels
Wheels are traditionally produced by milling or stamping and have parts hollowed out to make them lighter. The most common wheels have five arms from the centre and their teeth are created using a worm hob after machining or stamping. The quality is very high and they do not necessarily need finishing unless they are destined for very high-end pieces. To finish a wheel to the highest level, the arms of the wheels will be bevelled, the sinks polished, the faces sandblasted and then circular-grained or sunray-brushed (see below). Some wheels are also electroplated with nickel, rhodium or gold for aesthetic reasons and also to prevent the brass parts tarnishing.
Pinions and pivots
The pinions of pivots in a movement are generally made out of steel. They are produced on a profile turning machine before being hardened and then tempered (brought back to the required degree of hardening in Vickers). All the pieces are then burnished, which has both a functional and aesthetic role. The burnishing reduces friction, improves the transmission of force and produces a luminous effect. The traditional method of burnishing uses a special tool on a bow that will burnish the piece until the required dimension and polishing quality are achieved. In a high-end movement even the pinion teeth will be polished using a soft wooden disc made out of pearwood and coated with a very fine polishing mixture.
Screws that sparkle
Screws come in all shapes and sizes. They are generally produced in steel, but also come in gold, platinum and titanium. Their shapes also differ with cheese-head screws (for attaching the bridges to the plate), chamfer-head screws (for thin parts) and stepped screws or pivoting arbors (that need to maintain a certain amount of clearance after tightening). The screw head is particularly visible in a movement and will need to be polished and sometimes even chamfered around the rim and bevelled in the slot.
There are several methods for polishing screws from tumbling in a barrel with polishing agents to electro-polishing (whereby an electric current eats into the rough parts), brush polishing where the screws are polished on plates and lapping-machine polishing with the screws being polished on a plate by a grinding wheel or disc. It is also possible to polish screws entirely by hand using files, diamond paste, burnishers, Dugussit stones and lathes for an impeccable result. Some screws are also blued by heating them to over 290ºC for aesthetic purposes but also to provide an excellent anti-corrosion treatment.
Sunray brushing
This technique results in lines radiating from a central point, much like the rays of the sun. It is realized by means of a bell grinding-wheel that draws straight lines across the metal from the centre.
Snailing
Snailing is similar to sunray brushing but with spiral lines leaving from the centre, instead of straight lines. It is often seen on ratchets, bridge pavements, oscillating weights, barrels and barrel covers.
Circular grained
This form of finishing consists of fine circular lines that enhance the shine of a piece. It is mainly used on the visible faces of wheels and is achieved by turning the component and pressing against it with a slate stick or buff.
Cotes de Geneve
Engraving is a lengthy process which demands great skill so around the year 1880 watchmakers in Geneva designed the Cotes de Geneve pattern of straight lines to decorate some components and to hide any scratches or imperfections. The Cotes de Geneve motif is mainly seen on the visible surface of bridges and can be achieved with semi-automatic machines or CNC machines. There are two handcrafted methods, one that uses a rectifying ruler that scratches the surface, and the other uses a lathe that goes back and forth creating the stripes.
Mirror polishing
Mirror polishing is the technique where a component is so highly polished it appears like a mirror. It is also referred to as black polishing (as the pieces can also appear black), specular polishing, flat polishing and vertical polishing. This type of polishing is totally flat; the crystalline tips of the surface of the metal are torn off and pushed down by crushing, creating a perfectly flat surface. This flatness reflects the light in one unique direction, depending on which way the piece is facing.
The component can look black, grey or white and when assembled in a movement, gives a kaleidoscope effect. To achieve the effect is extremely time consuming. Modern methods include the use of abrasive papers or a lapping machine, but neither come close to the result of handcrafted mirror polishing.
A tourbillon bridge, for example, will be prepared using the abovementioned methods and then rubbed by hand using extremely fine abrasives on a zinc plate that is utterly flat. The process takes about two hours and the bridge will be assembled immediately after to avoid any scratches.
Engraving
Engraving bridges and movement components was popular in pocket watches not only for decoration but also to catch the dust. As movements were not water-resistant at the time, dust could become problematic in the movement. Handcrafted engraving has rough edges at the bottom of the grooves that would create a perfect dust trap.
Engraving are also a way to personalise a movement with drawings, motifs, names and reference numbers.
Nowadays many movements are engraved using CNC machines, chemicals, a pantograph machine (which copies from a stencil) or with lazer technology. Handcrafted engraving is achieved by making a drawing on the metal using a scriber, then the engraver will remove the material by making incisions into the metal with numerous different tools that range from blade-like scorpers to flat-edge gravers. “If you look at hand engraving close up, each line contains tremors, but it is these imperfections that catch the light and create a kaleidoscope effect – in comparison to engraving by machine which is dull and has no sparkle,” explains Papi.
Perlage
Perlage, stippling, spotting, beading or Oeil de Perdrix are some of the terms for the small circles that are often visible on the bridges, plates and at the bottoms of recesses. These small spiral-like circles are an excellent way to cover scratches an imperfections in components. There are few modern machines that can carry out this kind of decoration as they are extremely expensive. Most of the work is carried out on a stippling machine with an abrasive pad that will mark the surface with a swirl.
Guilloche or engine-turning
Guilloche is an ancient engraving technique that carves straight lines and/or curves onto the dial of a timepiece, case or other component. The name guilloche comes from French, and is believed to have been named after an engineer called “Guillot”. The first engine turning machines date back to the 15th century and were used for engraving wood and ivory. It wasn’t until the 18th century that artisans started to engrave precious metals in this way.
Hand guilloche is one of the most respected techniques as it is created manually using a traditional engine turning machine that removes the material with a turning tool. The guillocheur will start by ensuring that the metal is totally flat to avoid any distortion of the patterns. The metal will then be smoothed down and given a matt finish with a finishing paste in order to render the guiding marks more visible during the turning process. The difficulty is to keep the desired depth of the engraving and the contact between the tool and the metal constant for a perfect line – a momentary lapse in attention can be fatal.
There are two types of guilloche machines: a straight-line machine and a flinque engraving lathe for circular guilloche, and the possibilities for motifs with these two machines are limitless. Breguet has one of the most impressive guilloche departments with numerous guillocheur working on an array of antique machines. All of Breguet’s timepieces are decorated with hand guilloche with the brand’s Reveil du Tsar timepiece featuring seven different techniques. Some of the most common styles are clous de Paris (small pyramid motif), grains d’orge (barleycorn), panier (basket), soleil (sun ray), damier (checkered), but Breguet is always trying new designs. “The possibilities for new designs are just limitless,” shares the brand’s head guillocheur.
Taking a close look
Just one look inside Audemars Piguet’s Millenary Perpetual Calendar, or at Jaeger-LeCoultre’s Gyrotourbillon or hold a loupe to any of Breguet’s dials, or movements for that matter, and the numerous different crafts can be spotted immediately and admired. The time and expertise that has gone into each piece takes such movements to the highest level of horological standards. Some manufacturers claim that excessive polishing and finishing is unnecessary and even detrimental to the precision of a movement, but the winner of the last Chronometer Competition held by the watch museum in Le Locle was Jaeger-LeCoultre’s Master Tourbillon Calibre 978 and the second prize went to the brand’s Reverso Gyrotourbillon – both exhibiting some of the finest finishing and decoration. Hand finished and decorated movements come at a price, but it is price that includes uttermost beauty and savoir-faire, something that is rare in an age where profit so often rules over perfection.
