Last update Apr. 12th. 2016

Making of Suction Dies 

for Screw-back Case Opening-Closing

April 8th. 2016
  

 

To avoid scratching of the screw-back watch case one can, instead of the standard head, use suction dies in a standard press, like the one shown. 

This one, the MKS 220 was made in Japan by Meikosha.  

Suction dies are many, made from different materials in an attempt to increase friction between case back and die, and thus prevent slippage, and at the same time provide adequate moment force for closing the watch case properly.

    
Commercial sets of suction dies are rather expensive, and not all are good enough to justify the cost. 

Thus I investigated the available materials, at affordable cost, and have found and bought a set.

Originally this set was intended for camera lens repair, so there are several sizes unsuitable for watch use.

     
It took me a fair bit of time for careful consideration of the question of how to design simple set of cups that will hold silicon rubber pieces and not slip, without using any glues. 

To mount die cup holders in the press I needed an adaptor that would fit the ID of the cup, on one end, and to fit the press, on the other.

Obviously, aluminium was material to use, in fact I used Duralumin, adaptor was made from a rod 25 mm in diameter, 32 mm long

The finished adaptor in its place ready to accept one of the suction dies.
Looking at what is available, I decided to make die cups from thick wall Duralumin tubing 40 mm OD with the 10 mm thick wall. 

The finished cup, with the silicon rubber insert 32 mm in diameter, already cut off from the other half, the part 22 mm in diameter.

Cup's ID was made 0.5 mm smaller than is the OD of the silicon insert, providing enough friction between the cup wall and silicon insert  for prevention of slippage.

Second image shows insert press fitted inside the cup.

A newly made suction die, cup with the adaptor ready to be  mounted onto the press.
It was necessary to control the height of the suction die cup, so that when mounted onto the press, it would in full correspond with the normal working height.

The combined height of the die and the adaptor with the silicon insert protruding came to be exactly 59 mm, equalling the height of the standard press head.

The finished 32 mm suction die shown ready to use fitted onto the press.. 

The next step is to make a few additional dies with silicon inserts of different sizes.

My total investment was under $50 for all of the materials, plus few hours of my work on a rainy weekend afternoon.

To my utter satisfaction, DIY suction dies do work, quite nicely at that.

 
The three dies, sizes 28 mm, 32 mm and 36 mm made so far. 

The other planned sizes, the 22 mm, 25 mm and 41 mm will have to wait for the next coming rainy weekend afternoon.  

 
Having a larger lathe, one can turn die cups from a single piece of metal. 

I have used two part design, as shown above, only in order to reduce the boring of both ends of each die cup. 

This was achieved by using thick wall pipe having 20 mm ID and the use of adaptor fitting exactly the upper opening.

To save full size image, use mouse right click, then click "Save Image as".

 

 

Few of the intermediate sizes, 49-60 mm are very well suited for opening and closing of the American made PW, whose cases are not of the snap-on style, but are made to screw the parts together, either the back or bezel only, or both back and bezel.

Apparently these are big and strong, enough to be used as is, without having to make holding cup of metal, or any holder for that matter.

Tried and proven by opening few of the tough PW cases. 

 
The new MKS product, the watch case holders, made out of hard plastic. 

Designed to accommodate larger watch cases like the ones used on watches for diving.

Meikosha MKS article No. 19600 fitting nicely and securely in the base of the MKS 220 press, as shown in the second image.

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