There is nothing more unsightly than watch movement screws that have been hacked to oblivion my sloppy workmanship. It is, sadly, something that is seen far too often in watch movements that I come across. We can take the below Omega Speedmaster as a perfect example. This reference happened to be 2998-1, a very rare and expensive Speedmaster reference. You can see below how bad the screws were. Fortunately, all was not lost and the original screws could be polished.
Here is a close-up shot that was taken under a microscope to show just how bad these screws were.
To repair the damage I must first grind the screw head back so that the burrs and scratches are removed. It is vital that for grinding and polishing the screw is kept perfectly flat. To do this we use the humble bolt tool. It is a very simple tool which allows the screw to be mounted and then you can adjust the screws on the back of the tool so that when the screw to be polished is placed on the flat surface, it is parallel to the polishing block. Pictured here is the screw mounted in the bolt tool. To grind flat I use a 1200 grit diamond stone. Once the screw is flat polishing can commence.
Diamantine is the best compound to use which is to be mixed to the consistency of moist putty. You can use a general-purpose watch oil to make the mixture. Each screw takes around 15-20 mins to complete.
After much grinding and polishing here is the final result. You can see that all the burrs have been removed as well as the scratches on the surface. The reason the term ‘black polishing’ is used is that once the screw is polished it looks black when the light catches it at certain angles.
Here you can see all screws completed and then put back in the movement. It is certainly a labor-intensive exercise but as you can see, the result is definitely worth the effort.