Friday

Fridays are an odds and ends sort of day in watch school.  We only have class until noon and the morning hours are spent working on whatever you want.  We either play catchup with our watch overhauls or work on projects.

I have been working on an Atmos clock.  The technology of this clock allows it to be wound just by changed in temperature and barometric pressure.  Properly serviced one of these clocks can run for 30 years uninterrupted.  Last week I had installed the fine filament spring (seen below) into the regulator mechanism.  Today I ran everything through a couple cycles in the ultrasonic.  The main clock framework needs to be soaked in acetone to dissolve traces of the original laquer finish.  Once this is complete I can reassemble the clock.

Finally we've been working on gear train calculations in class.  Most of these are just basic algebra, but I hate hand-writing anything so I have begun to program these equations into my calculator which will save me a lot of time down the road.

Numbers and letters, together?!

Atmos balance assembly with spring

Chronographs

We've started working on chronographs in class.  These are the most complex watches we are going to touch during our watchmaking educations at NSCC.  The movement being used to introduce the class to the chronograph is the well built and extremely elegantly designed Lemania 861.  The other primary movement which we will be working on, and which is the focus of the SAWTA 4 test is the eta 7750 which we start in a couple weeks.

The chronograph mechanisms add a layer of complexity on what is basically a standard watch movement.  All of the normal adjustments (hairspring, endshakes, pallet adjustments) are all identical.  What I'm working on figuring out now are the oiling and servicing of the chronograph components. 

I will be working on these watches for the remaining 7 or so months of my education at the watch technology institute.  The goal is to achieve a total feel and comfort for working with these common mechanisms.  I will try and post a detailed overview of a complete chronograph servicing in the near future.

A lot more components!

The technical guide, this is the page illustrating the assembly and oiling of the base timekeeping mechanism

The pallet fork endshake had to be adjusted on my watch.  This is the same operation as on any other manual or automatic watch.

Useful Mnemonic

One of the things we are expected to memorize in watchmaking school are the 8 factors that affect the isochronism of a watch. With the help of a 'scrabble cheat' program on the internet, I came up with a very helpful mnemonic to remember these factors. Just remember to 'preempt friction'

P - Poise of hairspring
R - Regulating pins
E - Escapement
E - External Influence
M - Magnetism
P - Poise of balance
T - Temperature
and
Friction

Oil Spill

The last thing I tackled this last quarter was to change the battery on an oil-filled quartz watch.  Whoever had attempted this in the past has let an air bubble into the case and the watch had stopped.

After installing the battery the watch was still not working.  I am used to working on these movements.  It's essentially the same watch movement we had to complete on our SAWTA 2 tests.  So i took everything apart and during the process I dinged the coil and ruined it.  Replacing the board was not an option because this is a special 3 volt board with a custom battery holder.

No big deal, we have plenty of extra coils around.  So then began the painstaking process of melting off the existing solder and epoxy and soldering on a new coil.  This is difficult because the wires are VERY fine.  After about a half an hour I was able to get a new working coil installed.

This process is incredibly messy.  There was oil everywhere, all over my bench and my tools.  It was a very strange feeling getting oil all over a newly cleaned movement as that's usually exactly what you are trying to avoid.  At least putting the movement back together was quick because you didn't have to worry about oiling anything.

Once back together and ticking once again I refilled with oil, vacuumed most of the air out and we now have a watch that only has almost microscopic bubbles suspended in the mineral oil.  I've not figured out how to remove those yet, I'm guessing a stronger vacuum pump would help with that.

Oil-filled watch, complete with bubble

Even with a new battery the watch did not run, it needed an ovehaul

My vacuum platform, made mostly from scavenged materials helped pull some bubbles out of the oil.  The air compressor's pump does not draw a very efficient vacuum though so it was not as effective as it should have been.  We need a proper vacuum pump.

SAWTA 3

Three down,  one to go!

I passed my SAWTA 3 exam this week.  The test involves 4 parts:

1. Overhauling, repairing and casing of a 2824
2. 15 question theory
3. Case refinishing
4. Bracelet refinishing

Things went very smoothly this time around.  The only critique the examiner had for my watch was that I over-oiled the crown wheel and was a little light on the oiling for my lower balance pivot.  Besides that I got full marks!

The quarter is nearly finished, the last project I have on my plate is a cell change in an oil-filled quartz watch.   I am devising a vacuum system to make this simpler.  I will post soon.

Fixing a Levin Toolrest

The detent screw on one of our Levin lathes was stripped out rendering the part useless.  For my school volunteer hours this quarter I made a new post and installed it into the slide attachment.

The primary difficulty here was turning down the chunk of steel on a lathe using a 3-jaw chuck which didn't give me the best grip.  Unfortunately we don't have a lathe that can use a regular collet to accept these larger diameters.  Despite the cutter digging in and dislodging the workpiece on a couple of occasions I was able to turn the lower diameter down to where I could use a normal collet to hold the piece and finish forming the top.

To cut out the core I first used a end mill followed by some reamers on the Bridgeport milling machine in the basement. Finally, the detent hole and threads were formed using a drillbit and a simple tap.

The finished post, pressed into position

Overhaul/SAWTA 3 Practice

During the last couple of weeks I have been busy practicing overhauling and troubleshooting automatic movements.  Most commonly we've been working on the ETA 2824 as that's most likely the watch we'll receive for our SAWTA 3 examinations.

During the examination it is our task to troubleshoot issues with the watch which have been introduced by the examiners.  During dis-assembly you identify and fix the problems, then all that remains is to clean the watch and recase it with a high level of accuracy and cleanliness as both will be factors in the grading.

Besides the overhaul there is a written portion of the exam and a polishing exercise, both of which are proceeding nicely for.

I have taken some pictures of a practice overhaul and will offer a brief explanation of some of the steps below. 

The caseback has been removed

The rotor and stem have been removed, the movement can now come out of the case

Removing the hands while protecting the dial and hands with some plastic

The dial-side with the dial and date ring removed, nothing to repair on this side!

The hairspring is not centered, the coil spacing near 11oclock are wide and near 5 they are narrow, which will need to be corrected by bending the spring

Another shot, the dogleg in the spring near 12 o clock seems is where we will perform the correction

The entry pallet stone is not level in the fork, it has dipped out of its holder and needs to be reset so it can engage the escape wheel

The tilted stone

Using an electric heater and this expensive gauge it is easy to move the stones in or out of the pallet fork micro-metric amounts for precise depthing correction which is essential for a well-running watch

The endshake (up and down movement) of my pallet fork was too small, so here I am pressing the jewel back into its bridge.  Once the jewel was flush with the bridge the endshake was back within tolerance

Here I am adjusting the barrel endshake, which was also much too small.  Too little endshake reduces freedom of the wheels and introduces extra friction into the mechanism.

Here I have corrected the centerdness of the hairspring, looks slightly off here due to the balance being loose, once installed it is quite good.  Once the watch was reassembled the instantaneous rate and running characteristics of this movement were within 100% tolerance for this movement