How-to: the Mysterious Vostok hands mod.

Or to be a bit more precise, how to do a hands mod when the proper hands are not readily available.

Introduction:
The Vostok 2416b, 2414, and many other Vostok calibers require hands of the sizes:
Hour: 1.38-1.40 mm
Minute: 0.88-0.90mm
Second: 0.16mm or so.

Let's concentrate on the hour and minute hands today. A close match is the 1.50/0.90mm combination, used on many ETA and Seiko mechanical movements. I have selected a hand set from Otto Frei, at a cost of $4.00.

Today, I will demonstrate how to manipulate hand size, in the downward direction.

Tools that I will use:
Starting at the top left, and working right: Dust cover and movement holder, nitrile glove (non-powdered if you have one), dustblower, digital caliper, magnification, tweezer, pin vises, #50 Round smoothing broach, #60 Round smoothing broach, flat-across homemade hand setter, store-bought hand setter, dial protector, #6 Presto hand puller, stick pointed on one end and a glob of Rodico on the other, caseback tool, springar tool.



Other equipment used: Watchmakers lathe

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I start by de-casing the movement. This has been covered elsewhere by folks who take much better pictures than me, so I will spare you the details. We end up with the movement, still in it's spacer, in the movement holder. Dial protection is used, and we remove the hands with the hand puller.



We gather data. Use the dial protector! This Vostok has an hour pipe of Diameter 1.40mm, and a cannon pinion of diameter 0.9mm. So, we must modify the hour hand.

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Let's stop here and make an observation. Ask any machinist, we cannot make a hole smaller by removing metal. But most Hour and minute hands have a "stovepipe" extruded out the back. We will get this stovepipe to go smaller.



Let's get some more data. The outside of our "stovepipe" is 1.71mm.



I have a 1.6mm collet, and a 1.8mm collet. I choose the 1.8, and mount it in the headstock of the lathe. I use the tailstock to center and guide the "stovepipe" into the collet. Then we tighten the collet, and back off the tailstock. We tighten some more, squeezing the stovepipe until the hole is just a bit too small.


You don't have a watchmakers lathe, you say? Try the same technique using your pin vise. If the jaws are fairly sharp, and you exercise care, you can do it.



Keaton, our own Watchmaker-on-staff, once told me that one can also use the hairspring collet tightener tool for this same purpose.



Also, if a Seitz jeweling press is available, there is a special die designed for this same operation:


In my case, the idea is to go from 1.5mm to 1.4mm. It is a small amount of distance, but it makes a big difference on whether the hand will spin around loosely on the pipe, or not be able to be installed at all.

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There is a lot going on in this picture:

The smoothing broach is round, tapered, has a slightly rough surface, and has had some kind of heat treatment.

I have used the calipers to find the place where the diameter of the broach is 1.38mm. And, I have tightened the pin vise onto the broach at that precise location.

All I have to do is work the hand down, until the "stovepipe" reaches the jaws of the pin vise. I use a twisting motion as I do so.

The smoothing broach will burnish smooth, make round, and properly size the hand, in one operation. Be careful, work slowly, and be aware that watch hands will bend or break if too much torque is used.

If the minute hand needs modification, repeat the process.

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Let's try the hands. They now fit properly.

My preference is to hold the hands with Rodico as I use the hand setter. Also, I find myself frequently using one glove on my left hand. I can hold a movement with my left hand, without leaving fingerprints. Meanwhile, my right hand usually touches only the tools. It's a combo that works for me.


All three hands are on:






And, recase.


How about a gratuitous lume shot?


In conclusion, this operation can be risky. Damage to the hands can occur. Today, I was working with hands that cost $4.00. I am willing to risk ruining a $4.00 hand set, but I don't know if I would be willing to risk damage to a $20 or $30 set.



Edited 1 time(s). Last edit at 10/18/2010 12:22AM by Dave Murphy.