Hey Guys/Gals, I just finished reclaiming a pretty nice old Elgin keywind,that had been "had" by a "village blacksmith". So many broken pivots and bent wheels. Don't ya just love it when they just shovel all the parts in and screw down the plates without anything being in place. Anyway the hairspring looked like a bird's nest,so I had to replace it. I only had one Elgin hairspring and after all is done,the watch runs way too fast. About 6 minutes an hour fast. Is it proper to add weight to the balance wheel to correct that much error,or should I look for another hairspring. The watch runs good,the balance swings good,and has good motion. There are only 12 screws in the balance wheel,so plenty of room for more.

How close to the end of the hairspring is the stud pinned? If you can pin it closer to the end, that would help. You can vibrate the hairspring with tweezers, a domed crystal and a good stopwatch. Grab the hairspring near the end and let the balance hang over the crystal so it just touches the balance staff pivot. Start the balance oscillating and count either the clockwise or counterclockwise rotations for 30 seconds. 75 is the magic number. More than 75 and you are fast, less and you are slow. If fast, move the tweezer closer to the end and count again. If you can get reasonably close to 75 this way, then you want to pin the stud at this point. Adding weight will require poising of the balance and you still need to vibrate the hairspring to get where you want to be. This can be a very time consuming process and requires a lot of patience.

Hey Roger, The hairspring is pinned at it's end,can't make it any longer. The watch is together and running,and I have timed it with a stopwatch,and it gains 6 seconds every minute. I have a poising tool,and plenty of patience,and plenty of matched balance screws. I know they must be put in in pairs,and then the wheel poised,and I think I can do that. I don't understand the crystal and balance/vibrating thing. Wish I did. I spent a lot of time trying to straighten the original hairspring,but it is just too far gone. With my limited knowledge and ability,I really only have two options. More weight on the balance wheel,or a different hairspring.

Cecil,
It is hard to picture vibrating the balance, but if you do add weight, it will help you know how close you are without having to put the balance back in the watch each time to check. I'm sure you know this, but just in case, do not attempt to remove or add balance screws while the balance is still in the watch. The staff will surely break.

If you have the original Balance wheel for the replacement Hairspring, that should help tell you what weight is needed. In any event, 6 minutes an hour is about 19800 Beats Per Hour (BPH), or 1800 BPH too fast. A pair of "average" Balance weights added to the Balance wheel will reduce speed from about 200 - 400 BPH.

Try adding three or four pairs of Balance weights a pair at a time if you really want to see how they react the timing. Then if it is fast or slow within 100 BPH (about 30 seconds per hour), you may have to add timing washers or undercut the weights in pairs to bring it in time.

Also adding that much weight would well require re-poising the Balance wheel.

Hey Roger and David, Thank you for the advice and help. I got up early this morning and tackled the watch. After about 2 hours of trial and error, head scratching,Balance screws and poising,it now gains about .09 seconds per minute. I think that works out to about 1 second every 11 minutes or about 6 seconds an hour. That's one minute every 10 hours,which I think I can live with. I started it at 8am in unison with my electronic stopwatch, and I'm gonna let it run for a day or so in different positions to get it's kinks worked out,then if needed I'll try nudging the regulator a little,or maybe a couple of very light timing washers. I'll post a photo later today. It is really a beauty,in a pair case,which I have only seen one other before.