Tightening screws - how tight?

[Khan]

HiI have always wondered how to avoid signs of wear on screw notches when servicing a watch? Is it possible to service a watch and it after service looks untouched in the screw heads? I understand the factors like the layout of the screwdriver, in terms of width, thickness and depth should match the screw head. But can somebody explain how tight the screws should be tightened? Just enough to get it closed or slightly extra turn?

 

 

[anilv]

Use a properly sized screwdriver will help reduce marks but there will always be telltale marks but they will only be visible under a loupe.

As for how tight.. personally I screw it all the way and then a bit more. probably not more than a sixteenth of the diameter. The screws you have to watch out for are those with big flat heads with a small threaded portion. Eg ratchet wheels. Interestingly I was watching a video on YT where the watchmaker mentioned the ratchet wheel needs to be on tight as it is holding the tension of the mainspring. Actually its the square on the arbor/ratchet wheel which takes all the pressure. The screw just holds the two together.

Only screws that I screw really tight are those where the keyless has a rocking-bar mechanism.

Anilv

[mikepilk]

Very difficult to define. Nip them up, then a little more - as @anilv says.

The ratchet/crown wheel screws can be tricky, easy to break. I just serviced an old AS 984 where both the ratchet AND crown wheel were anticlockwise (both single slot, not three). I've never seen that on a ratchet wheel before. I could easily have broken it had I not realised. With tight screws I always try turning them back a bit to try to loosen them. That's how I figured out it was anticlockwise

[spectre6000]

The ones that stress me out are those acting on gaskets. You get them down snug, but then "tight" is anything but clear after that. I'm terrified of snapping a head off those screws.