Wednesday, April 11, 2012

Molnija 3602 wrist watch conversion Part 1

Next on my radar of movements to poke around on is the Molnija (Lightning in Russian, thanks David!) 360x series of movements. The 360x series is the Russian copy of the Cortebert 616 and has three models available, the 3601, 3602, and 3603 and they are separated as such:

01: antishock, but no second hand (I have however seen 3601 with a subdial)
02: second hand in subdial, no antishock
03: second hand in subdial, with antishock

The first two digits of the model indicates the size of the movement and the last two the variation within the model range. It is nice to be able to work on this movement without having to pay for the cost of a Cortebert movement.

The pocket watch I bought on ebay had a plain printed dial and the subdial is not sunk like I am used to seeing on Hamilton 10 size watch dials.

Seeing that the dial is one solid piece, it is an ideal candidate for my water slide watch dial application, and the movement below the dial is a pretty plain Jane looking surface.

I decided to keep the original hands and re-use them as they have maintained their bluing but the stem would have to be replaced. At first I planned on cutting down the original stem but than as I inspected it closer, I came to find that the threads for the crown are tapped only for the crown at the top of the stem and is not threaded all the way down like you would see on a 6497 stem.

I have no source for NOS Molnija stems so I started to compare a 6497 stem to the original stem from the watch and came to find that the thread diameter is the same but the square part of the stem that engages the winding trunnion and the un-threaded part right above the square parts (can be seen in the picture above) were what was preventing the 6497 stem from fitting the Molnija. They were only slightly too big to fit, as in .04mm too big at the square part and about the same at the round part. I decided to apply my 1911 building skills of slowly fitting metal parts together by gently and slowly filing and fitting but in this case; lapping with a diamond lap and keep measuring and comparing with a pair of calipers. You can see the fitted stem on the left in the photo below.

After about an hour of lapping and filing, I was able to fit the 6497 stem to the watch. Now on to fitting for a case.

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