Personally, I think the Swiss style
stop-work mechanism, if used in a watch this small, would be likely to
fail. The force placed on the tiny parts during manual winding could be
overwhelming causing deformation of the parts or sheering of the boss
on the thin barrel lid. You can see from this photo of the movement placed
on a dime that the mechanism is very small. This is the smallest cylinder
watch I have ever seen. Making and fitting a cylinder is a demanding job
and one this small is more so. |
|
|
A cylinder must be the right size inside and outside in
order to interact properly with the escape wheel teeth.
The dimensions are determined by the space between the teeth and
the width of the tooth. The outside diameter of this cylinder is
close to 0.50mm. The inside
is very near 0.35mm. That leaves the wall thickness at about 0.075mm.
It must also be hardened and polished in order to reduce wear and
friction or the watch will not run for long if at all.
Temper must be drawn from the ends to allow the plugs to enter
without fracturing the cylinder.
|
The opening must also be precisely positioned. This is especially
true of this watch because it has no provision for depth adjustment
as with the usual chariot (an arrangement that allows the balance to
be moved in relation to the escape wheel) found on other watches of
this type.
|
After
carefully measuring the movement dimensions and making a drawing of the
missing cylinder, the cylinder was produced using a WW pattern, American
Style, Watchmakers lathe. I
used oil hardening drill rod reduced to about 0.80mm diameter.
First the blank was drilled with a #80 drill producing a hole about
0.33mm diameter. Then it
was parted off at just slightly over finished length.
I made three of these blanks while I was at it.
Often something goes wrong during a later step in the production.
It is great to have an extra blank on hand.
Next the blanks were strung on a tense steel wire charged with
oilstone powder and worked back and forth to dress the holes, smoothing
and removing burs etc. Then the blanks were rinsed with ultrasonic action in solvent.
I made a mandrel by placing a hardened and tempered steel wire
in the lathe and turned it carefully to accept the blank and be supported
at the end by the tailstock center.
The blank was placed on the mandrel, cut, ground to length and
about 0.52 mm diameter. This
produced the rough cylinder (concentric) with evenly distributed wall
thickness. |
The
cut out of the cylinder was done very carefully with a custom made lap,
charged with oilstone powder, while it was on the mandrel. Removed from
mandrel, the piece was placed on a strait, close fitting wire and hardened.
It was then tempered to a straw color.
The result is shown next to the point of a sewing pin.
Hardening and tempering is a process, described in many references
for Watch making, involving the use of heat to “heat treat” the carbon
steel part. |
|
|
Shown
with a dime from left to right are the balance wheel, escape wheel, blank
steel piece (like from which the cylinder was made), cylinder after hardening,
and head of a common sewing “straight pin”. |
It was necessary to temper (soften) the ends of the hardened steel cylinder
because small plugs must be pressed into the ends to form the pivots. Leaving
the cylinder hard where the escape wheel teeth make contact is the trick.
The photo shows the color changes that took place as a result of the
heat that was applied during the tempering process This was done by
heating the wire, first one side then the other, and watching the color
change travel down the wire until it affected only the desired portion
of the cylinder.
|
|
|
Finally
the part was lapped and polished to finished size inside and out. The
finished part is shown in the photo on the right.
Plugs
(tampons) were then made from hardened and tempered
steel. Very
carefully they were fitted into the cylinder and the pivots were turned
and finished as with a more common staff.
The pivot size for this small watch is .07mm similar to a modern
wristwatch.
|
| I am constantly amazed at the achievements of the very talented craftsmen
who refined the Art of Watch making
I have a deep respect for those who have gone before.
It has been my privilege to restore wonderful creations made long
ago, often prior to the machine age.
Many of them were made with hand and foot powered tools using natural
lighting or oil burning lamps. |
Early watches were not designed with
the help of advanced engineering concepts but more by trial and error.
Many years of seeing what worked and trying a better idea lead to
a better and better product. The
miracle will continue. |
