I have a fairly nice Elgin 18S BWR that I have been tinkering with for several months. The problem--it continues to gain time. I have cleaned it, added a new mainspring, and checked it over with no problems found. It gains about 7-8 minutes in a 24 hour period. I've waited before doing anything with the balance. On the balance wheel the meantime screws are crewed the whole way in. My question--How many minute change can I expect with one complete turn of the meantime screws?

Tom

Tom,
The amount of timing change per turn of a pair of meantime screws isn't published because it will vary from watch to watch, depending on the strength of the hairspring and the total mass of the balance.
Best bet is to turn one pair of screws out one turn each and see how much change there is in the watch's rate.
BTW, I've found that many Elgins do NOT have meantime screws, even the 21 and 23 jewel high grade movements. Are you sure that there are meantime screws on your BWR?

Hi Ed, I went back and eyeballed that watch again. How right you are. They are not meantime screws, but regular balance screws. What do you recommend? Do I add some washers?

Tom

I don't collect Elgin, per se, but I do have some of them. Most of my Elgin watches are hunters with fancy dials. Most do not have mean-time screws.

There are always timing-screw washers. The come in different weights marked in minutes. They can only be used to slow a watch and only to a certain extent. If you load the balance wheel too much it will wobble.

A couple notes. First, the washers come marked in minutes and will (roughly) slow the watch that much. But... you must use TWO washers, at opposite ends of the balance wheel to achieve that timing adjustment. Second, the timing screws have a cut, like regular screws but I would caution against using a screwdriver on them. The pressure of a screw-driver could bend the balance wheel. And... They are very soft and difficult to handle. Instead, I remove them, add washers and reinstall them with a pin-vise.

Speeding up such a watch is more difficult. One way is to undercut the timing screws, removing metal on the screw side and then taping the area.

Theoretically, bending a balance wheel (cut) inward will speed it up but.... it will take the wheel out of true and cause a new set of problems.

Thanks Peter, I have several small vials of washers. Will check to see what I have. I always use a pinvise when removing or installing small screws. Will let you all know what happens when I get to it.

Tom

Tom, could it be the wrong hairspring; a replacement.
Could it be slowed down by adding balance screws.

Just throwing a couple of things out there to chew-on.

Frank

That's true.

And.... even a gummed-up hairspring will do it. If a hairspring is dirty or improperly cleaned, a couple of turns can stick together. The result is the same as if you had cut an entire piece of the mainspring off. It acts like it's much shorter and faster.

It would be like taking inches off a clock pendulum.

Thanks guys. I went back and closely inspected the hairspring. It is definitely an original Elgin hairspring, and it is clean. Now--Has it been cut and restudded sometime in the past? Who knows? We'll continue to play with it.

Tom