We’re on the road to our next exam, Geartrain Servicing, on 7th June. That means one mock exam per week and practice, practice, practice. Straightening bent wheels, setting jewels to give the correct end-shake, cleaning, oiling and assembling.
It’s repetitive but that’s the point. I’m getting better at judging oil volume and placement, especially on the escapement.
I’m getting better at judging jewel settings.
I’m getting better at fault-finding.
I’m getting better.
Back to servicing.
Started this week with a quick refresher servicing the ETA 6498 to get back into oiling, etc after burnishing and polishing.
Then it was an introduction to the last couple of skills we need for the upcoming gear train exam. First of all we had to learn how to adjust the tightness of the cannon pinion. This is extremely important as this pinion acts as a slipping clutch, holding the minute hand during normal running and slipping around the centre wheel arbor when setting the time.
Adjusting the cannon pinion is a fairly primitive procedure for such a precise operation. Tightening involves placing the pinion between two chisel-shaped jaws and hitting the top one with a hammer to pinch the pinion. Loosening involves broaching it out from the inside. It’s tricky but possible. I proved it!
Secondly, we learned the methods used to precisely shorten the winding stem and then fix and true the crown. Strong side cutters and an India stone sort the stem out, a leather mallet takes care of the crown.
Those tasks completed successfully, we had our first mock exam on the gear train. We each received a brand new movement, case, dial, hands and crown. One of the instructors had previously bent wheels and misaligned jewels in the movement. The exam set an 8 hour time limit to disassemble the movement, correct any faults, clean, lubricate and assemble the movement and then fit dial and hands, case up and fit the crown and stem. The first time I had ever carried out the complete procedure.
I’m pleased to say, I passed with flying colours. A few things to be improved upon but that’s what mock exams are for.
A very productive week and one that I thoroughly enjoyed. I could do this for a living!
Time to do some more work on the WOSTEP WO1 watch. We’ve made the winding stem and balance staff, now we need to work on the bridges.
The bridges are supplied machine-finished which means they’ll work fine but don’t look great. It’s hand-finishing which separates the mediocre and the functional from the great and the beautiful.
The first step is to flatten the upper and lower surfaces on paper. This improves the appearance by leaving a grained finish but (more importantly) ensures the surface is flat. The aesthetics can be further improved later but you need to start work with a level playing field.
Next is flattening the sides. Trickier as it’s vital to retain the sharp corners to give the best appearance. For this we use a piece of brass bar, faced off at each end in the lathe so as to ensure the ends are flat and at 90 degrees to the sides. Placing the work piece on the bench, you can then wrap paper around the brass and carefully work the flanks to the same grained finish as the upper and lower surfaces.
Once the sides and uppers are free from machine marks, the next step is to polish the countersinks in the screw holes and jewel holes. A circular cutter is used to give a consistent finish and then a piece of peg wood is shaped so that it matches the shape of the countersinks. The peg wood is then mounted in the lathe and diamond polishing paste applied. After that, you just push the peg wood into the countersinks and – voila – a polished finish.
Finger cots stop you touching the work piece with your skin. Grease and acid on the surface of the skin will tarnish German silver in hours. A finger print can permanently etch itself into the metal if left!
Things relaxed a little on the run up to the Easter break which gave the opportunity for the class to work on our choice of side projects. Some elected to make tools, others chose to work on their school project watch. A couple of us had watches of our own that needed a little tlc.
I decided to service my Smiths 1215, acquired from eBay last year. Sadly neglected and a little worse for wear, I’d stuck it on a strap and put it to one side until a time like this.
The watch is historically significant as, apart from being English made (something which is of huge appeal to me), a slightly modified version of this model was supplied to Edmund Hillary’s 1953 Everest expedition. Smiths watches were the first on the summit of the highest mountain on Earth.
After stripping it down, a couple of issues became apparent. Firstly, the setting lever spring had snapped. This isn’t a big problem, they’re still made for this movement and not at all expensive.
Secondly, the mainspring had set. Instead of springing into a nice long ‘S’ shape when removed from the barrel, it stayed tightly coiled. The watch would still tick but the duration of run would be terrible.
Again, no big deal as replacements are available. In addition, I’m going to replace the crystal. As is common on watches of this type and age, the ‘crystal’ is a dome of plexiglass or acrylic and is really prone to scratching. Replacing it will freshen things up and allow a clear view of the dial which has aged very nicely.
The whole thing has now been through the cleaner and will be lubricated and reassembled when the new parts arrive. Something to look forward to.
I’m talking oil. Specifically which oil, how much and EXACTLY where it needs to go.
After much dry stripping and reassembling of the 6498, it’s time to start oiling. First things first, oiling the shock settings that support either end of the balance staff.
To get the practice in without having to keep cleaning the watch, we use a plate with 20 incabloc settings mounted in it. After setting the jewels at the right height, the task is to apply a precise quantity of oil dead centre on the ruby end-cap and then mount the ruby into its setting. After a few practice runs under the tutor’s supervision, we have to implement our own quality control. Oil all 20 jewels perfectly and submit them for inspection. Any mistake on any one of the settings gets the plate dunked in alcohol so the whole lot has to go into the cleaning machine to be started again. Complete the whole plate successfully 5 times and you’re done! 100 jewels straight with no mistakes sure gets your eye in!
Then it’s on to servicing the whole movement. Stripping, cleaning, lubricating and reassembling the keyless work, train and escapement.
Repetition, repetition, repetition. I invested in a finer oiling needle than those supplied in our school toolkit and moved to working under a 30x microscope. Accurate placing is so much easier than trying with an eye glass in.
I’m getting better with practice but could still do with a little more finesse, especially on the escape wheel teeth. Pushing a ‘needle’ with a bead of oil on the tip into a watch movement and ensuring that oil only ends up in the intended place is an acquired skill. I need a few more goes yet.