Technique → Movement

MAINPLATE

Together with bridges and pillars, it is part of the so-called movement cage, not to be confused with tourbillon cage. Mainplate is the base plate of the movement, which can also be compared to the movement’s chassis.

In the majority of cases it is made of brass, sometimes for some higher end models in german silver, and more rarely in gold. The mainplate is drilled, turned, milled and then stacked to accommodate the various components of the movement and it can be decorated, sometimes skeletonized, often rhodium-plated or gilded.

It is often round but it can take the shape of the box in which it will be fitted. Thus we can sometimes see plates of barrel shape or rectangular shape for example.

It is an essential component of the movement and easy to identify. The mainplate is usually the largest component of a watch movement.

The manufacturing techniques of turntables have evolved over time. Once made on chisels, they were then made on more sophisticated lathes and are now produced for a large part of the production on numerically controlled machines.

The evolution of the watchmaking techniques also made its aspect evolve. With the arrival of the extra-flat watches, movements with a suspended barrel maintained only on the bridge side have emerged. These mainplates equipped with a suspended barrel mechanism are easily recognizable because they have a large opening at the location of the barrel. Also in the holes of the mainplate one can almost see a starry sky with its constellations.

Historically, but also regularly nowadays, three holes are almost always identifiable because they are aligned on a line. These are the three holes of the three main components of the escapement, which are the balance wheel, the pallets and the escape wheel.

It is sometimes shaped for watches that are not round, so custom made.

Advantages:

Disadvantages:

For the artisanal method, the plates are machined with more care. Thus, we will be able for example to make sure to make sinks around the perfectly polished stones which will come exactly to the level of the stones and will let enter the light in the rubies and give a splendid glare.

The same attention can be given to all other rough edges around the screw heads for example but also at the end of the screw holes, still to improve the reflection and the aesthetics, this time around the screws. Also, the surfaces can be decorated with attention.

The decoration mainly given to a plate is the circular graining (perlage). For this method of manufacture the plates can be made on a lathe type 70 and also a milling machine for the part of the winder under the dial.

For the purists who wish to use the energy of their own arm, the mainplate can also be produced on a face-lathe.

For the semi-manufactured method, what is called reworking is often done. The plates will often be produced on numerical controls.

To compensate for the smaller quantities than the industrial method, a numerical control will be programmed once, which can produce several years’ worth of parts in a few days. Then these blanks will be stored and taken back one by one to refine their finishes.

For the industrial method, the plates will all be machined on numerical controls working sometimes non-stop and even at night. The only interventions on these machines will be the supply of materials to machine the parts and the exchange of worn tools.

Indeed, on this type of production line, a drill will drill a smaller hole a few hours later than the first one, this is simply due to the wear of the tool. These aspects of tool wear are always to be observed among many other aspects of this manufacturing technique.

In this manufacturing method, the plates will not be adjusted one by one, but will be worked with the method of tolerances which, even when they are extreme, produce a functional object.