Scale Balance Model

Our next manufacturing project in class was to take a balance wheel and its staff out of a ETA 6497 movement.  Then we were to measure it, and scale it up 2x in our plans and manufacture it.

The design of the bridge and the wheel were up to us as long as we kept to general tolerances.  I decided to make an impractical iron cross balance wheel which turned out okay, but does require some final finishing.  I opted to machine the bridges out of solid chunks of brass rather than using a spacer so I got to spend some time with the mill.  The process is more time consuming but provides superior durability overall.

The only thing that remains, other than final finishing is to finish the balance staff (the axis pivot that the balance wheel pivots with).  The staff is machined out of hardened and blued steel which is more difficult to cut than untreated steel so I ordered an indexed carbide cutter which should arrive sometime tomorrow and make the turning of that part much easier.

Once I have completed this project I will post pictures of the assembled product.

Milling out the bridge plate

Finished balance wheel, bridge, plate, and cap jewel holders (without jewels)

Overhaul

     This week we have been practicing overhauling a simple watch movement. This involves identifying potential problems while disassembling the watch then running it through a mechanical cleaner. Once the watch has been cleaned it must be lubricated and reassembled while maintaining a meticulous level of cleanliness. The trick here is to make sure you don't get even a single smudge anywhere on the watch and to keep an eye out for lint/hair/dandruff/dust etc. that floats down and contaminates the watch. Then you must ensure that the miniscule amounts of oil you are applying are in exactly the right location and quantity. It is a challenge, but I have improved greatly in just a few days of practices.

     Some issues I encountered with my particular watch included:
1. The third wheel was not true and had to be flattened
2. The guard pin on the pallet fork was too low in relation to the safety roller on the pallet staff and had to be adjusted
3. The entrance jewel on the pallet fork was seated too shallow and was causing excessive amplitude and had to be adjusted
4. The regulation pins on the balance were set too wide causing an out of rate situation in vertical orientations

Each operation that brings the watch back to perfect working order has its own procedure and special tools. It will be interesting to see how well the watch keeps time once all of the adjustments are done and I have it assembled in a final state. I will post the timing results here once I get them.

 Mainspring winder set

 Mainspring winder

 Wound mainspring

 ACS 900 cleaning baskets

 Cleaning baskets in harness

Lubricating the mainspring

More STEMS

This week I did nothing but make winding stems.  This is extremely good lathe practice.  I have perfected all of my techniques to complete the task other than the hardening of the smallest stem which keeps warping on me.  I've had to get a much better edge on my cutters to get the small diameters required, if the cutter isn't sharp enough the piece is just deflected by the tool and it breaks off.  The steps required to make a stem are as follows, I do them in this order:

1. Use a hand graver to put a 90dg point on the end of the steel rod
2. Machine the smallest diameter on the end of the rod, our smallest so far is .35mm (still fairly large)
3. Machine the section where the square will be filed
4. File the squares
5. Cut rod to proper length then use a hand graver to add a 90dg point to the other side
6. Turn the diameter to be threaded
7. Apply threads
8. Harden steel rod (use hardening tube)
9. Remove scale with sandpaper
10. Temper steel rod
11. Machine the slot in the middle of the stem
12. Add the smaller stepped diameter behind the squares
13. Turn the final diameter on the middle of the stem
14. Finish with fine grain sandpaper

It's quite a process, and something can, and periodically does go wrong on every single step which requires restarting.

Some threads after running the steel through the die

A freshly tempered winding stem

Hardening the steel stem, using the protective tube

The steel hardening tube

Winding Stem

Winter break is over and the first project of the new quarter is to start working on manufacturing winding stems.  After two days I nearly have the first one down to an acceptable level of finish.