The smallest part in the NH55!

 

Small parts will never cease to fascinate me. Good thing watchmaking is my profession! There will never be a dull day. The smallest part in the NH55 is the banking pin. Funnily enough, it's also the part that requires the most accuracy, a shift of just 1-2 microns in the shape of the part can have a very large effect on the timekeeping performance of the watch. The banking pin is pressed into the mainplate of the watch, and acts as an endstop/travel limit for the movement of a part called the pallet fork. The larger this pin, the less travel the pallet fork has, the smaller the pin, the further the pallet fork can move. In this way, the diameter of the banking pin plays a crucial role in the timekeeping performance of the watch, and therefore demands a lot of attention in the manufacturing process.  The business end of the banking pin is 0.4mm in diameter. Nominally, 400 microns, but during the assembly process it can sometimes happen that the watchmaker putting the watch together needs a smaller or larger pin, to adjust the travel limits of the pallet fork. It's for this reason we have to make the same pin, in a series of small increments. Each banking pin is measured and sorted in each bin. This does slightly relax the demand on the manufacturing process, and allows for a little more of a shotgun approach, but if anyone has ever read or knows about tolerance matching in assemblies, then you'll understand that the "ease" is a double edged sword.

For example, what happens when you need many more pins of a specific diameter!? You don't really want to shotgun your production and have every 10th pin be the one you need, and have piles of pins that will never be used. On the contrary, it's much better if the manufacturing process is accurate enough so that you can manufacture within the tolerance band (just +- 1um!), at any given time.  So, how are they made?  The parts start off as 3.00mm round bar, of a very specific grade of material, LAW100pb. The bars are 3m long and are supported hydrostatically by a bar feeder as they enter into our Citizen R04 lathe. The R04 is the first machine we purchased, all the way back in 2016!

As the material enters the lathe it is introduced to cutting tools - these cutting tools are so sharp that they are actually lapped with a fine diamond slurry so that the cutting edges peel off material with almost no force. This is very important since the forces in the cutting processes has a large impact on the final dimensions of the part. Too much force, and the parts will deflect and be pushed out of tolerance.

Oil cools and lubricates the machining process, and ensures long tool life and great surface finishes.

Once the turning process is complete, the part is cut off its parent bar and sucked into a parts catcher, the parts are then collected and are ready to be measured.

All of these processes are very finely tuned... From the lapping of the cutting tool, to the selection of what material is used, to the program that runs the CNC lathe, to the handling of the part during measurement, to the installation in the mainplate... There is virtually zero room for error. Every time there is some disturbance in the process, a dull tool, low quality material, incorrectly calibrated measuring equipment, etc, the effects are felt throughout the entire process. Ultimately, in the end, by you!  Josh