08
MAR
2016

Getting Real

One year into the dual system program we are approaching the more advanced regions of our profession. On the watch repair side we left the 7750 behind and turned towards more traditional chronograph designs, while on the micromechanics side in addition to working at an increasingly smaller scale we are moving into areas that require heat treatment to create steel components whose elastic properties match their intended purpose, like set lever jumpers or similar watch parts with spring like action.

When we combine these two areas of watchmaking that are typically kept apart in educational settings, something beautiful is happening: a highly efficient learning takes place. The reasons for this are rooted in the principles of adult education. However since you are probably reading this blog because you are interested in watchmaking and not in pedagogy, I will not go on any further here about the teaching aspects. In case you want to go a bit deeper into the matter, here is a list of some Pedagogy Titles in random order, just like they are living in my bookshelf.

I want to give you here a brief outline of this two week (168 hrs) block:

We started the session with several “warm-up” services of a 7750. This serves the purpose of calibrating the group of learners – the 10 week intervals between the sessions could cause some drifting when it comes to perception, procedures, criteria, etc.

After that we went straight into a micromechanics centered session: Starting at a relatively large scale we made a useful tool that would be needed later: a screw head polisher. The new design made it an interesting challenge when it comes to tracing and filing; and even consulted with our friend Pythagoras about the best way to make a tracing pattern from the information given by the technical drawing.

Figuring out the tracing pattern from the technical drawing

 

Tracing

Sawing along the traced lines

 

 

 

 

 

 

 

 

 

Focused workstyle and motion blur

After the pieces were roughed out with the jewelers saw we brought them to completion by filing.

 

Bringing the workpiece to final dimensions

While maintaining flatness and the 90 degree angles

 

 

 

 

 

 

 

 

 

 

Checking the angles using a right angle gauge

Cutting the threads

 

 

 

 

 

 

 

 

 

 

 

Applying the bevel – note the fine tracing line as a reference

 

After some more minor lathe work the screw head polisher was completed and waiting for its first job, which I will show you in a moment.

 

After the completion of the screw head polisher it was time to leave the large scale work behind and continue with smaller objects of more challenging material: we broke the set lever jumpers of our school watches (based on cal 6497), simulating a common scenario when servicing vintage watches. Frequently replacement parts in that category are not available any more and the watch service professional has no choice but creating the piece by hand. Here some images of this process:

 

The original (broken) jumper (in the back) serves as a template for roughing out the new one. The two pieces are held together by jig glue. (Shellac is not recommended for this purpose as its hardness will compromise your cutting tool.)

A roughed out set lever jumper and the broken original.

 

 

 

 

 

 

 

 

 

 

Heat treatment: quenching of the workpiece for the hardening process by sandwiching it between two anvils covered with oil in order to reduce the risk of warping from uneven cooling.

Heat treatment: Tempering the workpiece to blue. The brass shavings help to distribute the heat evenly.

 

 

 

 

 

 

 

 

 

 

Filing the workpiece to final shape

Close inspection during the final stage

 

 

 

 

 

 

 

 

 

At this stage the workpiece is almost completed. There is possibly some work on the jumper profile necessary in order to achieve the “right feel” when switching between setting and winding

 

Once the set lever jumpers were shaped, finished and ‘fine tuned’, we moved on one level higher. The very first chronograph that I worked on was a 7734. It was an extracurricular activity at my watchmaking school. The teacher handed me a box with unsorted parts from various calibers and asked me to put a working movement together. It took a while, but every minute of this task was a worthwhile investment. This approach makes you reflect the interaction of the various components very thoroughly, resulting in COMPREHENSION of the complex mechanism.

I wanted to create a similar learning experience for my dual system students as an introduction to a Lemania chronograph movement and “misadjusted” the hammer to a degree that made a replacement necessary. Under the assumption that no replacement parts were readily available the students had to create the replacement hammer by hand.

The hammer interacts with seven different areas: its bearing, the contact point for the hammer spring, the contact point to the cam, the contact area for the lock, the contact point for the stem bolt, and of course the two contact points for the heart cams. These kind of hammers require adjustment by filing when they are installed into a movement, and careless work in this context will render the part useless.  That was exactly the “misadjustment” that  I introduced.

That means, the new hammer can not be copied from the old one when it comes to the hammer faces, but has to be shaped and fine tuned by observing the geometric relationships with the interacting components – the heart cams of minute counter and chrono runner. As mentioned before – overall there are seven areas of interaction, necessitating a comprehensive reflection (and understanding) of the entire mechanism when creating a functioning hammer. The learner develops awareness of essential details that would not be noticed in the course of a paint by number approach.

Here you see our journey in images:

 

Getting ready for working on the movement: hand removal

Diagnosis of error in the chronograph mechanism

 

 

 

 

 

 

 

 

 

 

 

The old hammer is used as a template to rough out the new one. An exact copy is not possible since the faces of the old one are dysfunctional, necessitating the final adjustment within the movement

 

Test fitting the workpiece. The pin for the hammer spring is not installed yet and the bushing is just friction fit instead of riveted as it needs to be taken out again later to apply the surface finish. It is evident that the hammer faces still need some work

 

Finishing the sides of the hammer with a fine Degussit stone

 

Finishing the sides of the hammer using an oval burnisher

 

Adjusting the flat polisher. The red ink helps indicate the amount of surface contact between the workpiece and the lapping film / sandpaper

The flat polisher in action

 

 

 

 

 

 

 

 

 

 

Surface finish completed (this flat polisher uses a square carrier, the other one uses a round one – personal preference of the watchmaker). The piece of wood on the left side in the foreground serves as a guide to achieve a straight line finish

 

Bushing and pin for hammer spring installed

 

Hand crafted hammer installed in movement for final functionality check. Now the rest of the chrono functions will be adjusted and the movement disassembled for cleaning

 

Reassembly

This concludes the session. The students leave with a solid understanding of this chronograph mechanism, advanced skills and knowledge in hand crafting watch components, an increased level of love and passion for the profession and an appreciation for life long learning.