Static poising, heavy spot at mean time screw

[mbwatch]

I am attempting my first static poising on a low grade 7 jewel Waltham pocket watch. I made a few corrections to the balance screws with an undercutting tool, successfully. But the last position where it is very slightly heavy is landing on one of the mean time screws.

How do I deal with this? It is not significantly heavy there, the balance just comes to rest gradually with one mean time screw down. I assume I should not try to cut down that screw or add a washer. Would it make a difference if I brought the mean time screw in a quarter turn? (I assume not since it isn't in motion)

[Klassiker]

6 hours ago, mbwatch said:

Would it make a difference if I brought the mean time screw in a quarter turn? (I assume not since it isn't in motion)

It will make a difference. Try it and see.

[JohnR725]

Yes you definitely do not want to physically modify the mean time screws but they are movable. Plus you get some interesting combinations if you move both of them. In other words the one is heavy could go in a little bit and the one on the other side could go out a little bit.

[mbwatch]

7 hours ago, Klassiker said:

It will make a difference. Try it and see.

 

3 hours ago, JohnR725 said:

Plus you get some interesting combinations if you move both of them

Thanks to you both. Ultimately this is probably a moot point. I did the static poising to where it landed on the mean time screw and then reassembled everything later yesterday to find it running at +480 a few hours after posting this. So I think I'm going to try adding some timing washers first to get the rate down. And experiment with the timing screws again when it is back into poise.

[JohnR725]

5 hours ago, mbwatch said:

everything later yesterday to find it running at +480

This unfortunately is the classic problem of poising. Ideally the balance wheel left the factory reasonably poised over time interesting but not always good things have happened to a balance wheel. It would actually be nice before static poising to figure out where you stand so you know as to whether you going to be adding weight or the consequences of removing more weight. But at least you know where you stand now and you can add timing washers. Then you can still use the mean time screws to fine tune things at the very end.

[mbwatch]

7 hours ago, JohnR725 said:

before static poising to figure out where you stand

Absolutely lesson learned, next time it will be on the tg before I poise it. Thanks for all the suggestions.

Edited August 6 by mbwatch

[mbwatch]

I had time to return to this watch today. I added 2 sets of 3min timing washers and brought it down to +60 where I could get it into what seems to be a good static poise. Once I got it in beat to 0.3ms it is running great in all positions except a 40s delta pendant up.

I would prefer if that error was any position other than PU but as a first try and on a worn out old 7 jewel watch I am going to stop here and take the win.

Edited August 10 by mbwatch