If you replace the main spring with a stiffer/stronger one, it will make it harder to wind, but will it also make a watch run faster, and vice-versa with a weaker one? Any idea how much?
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The weaker spring can make the escapement cycle a little faster because there is less pressure on the pallet jewels lowering the "flip" power to the balance wheel roller jewel, meaning the kick to the swing of the balance wheel is lighter and the rotation shorter, and hence (in some cases) the speed increases with the shorter cycle period of the wheel.

A too stiff mainspring is not good for any of the parts and may stall the movement. If you check the thickness and width of the mainspring and it matches others for the same type movements, there are usually none of the above type problems.

If it did anything, the stronger spring would make the watch run slower, not faster. It would theoretically increase the force on the gear train which would make the balance wheel have a greater amplitude of motion which would slow down the escapement.

It's probably not a good thing to do in any case.

Hi Donald

Have you checked the regulator pins ? Bend or very narrow ? Is the hairspring free (in the middle of the pins when the balance wheel is neutral)? Does the hairspring touch the pins on equal arcs when turned right or left ?

Regards
Gerald

First,

Don...greater amplitude will NOT cause slowing of the escapement. The vibrating of a hairspring is much like a tuning fork. Regardless of how much it vibrates, it still gives the same pitch.

The watch in question could need service, but I would demagnetize it as well which should be a part of every service.

Paul, Seeing the watch in question brings me to believe that this is NOT a mainspring issue.

First, Your watch uses a mainspring which is made especially for that motor (safety) barrel.

Second, in another post, I mentioned the regulator (especially on higher end watches) can have little or NO influence on the watch timing. In your watch which is running 10 seconds (only) "fast"/day this is certainly the case. Remember, <5 seconds/day would be within RR time standards.

A. Put the regulator back in the middle.
B. If you have the tools, Turn 2 of the Mean time screws out 1/4 turn and check time again in 24 hrs.
C. If that does not work, send it to Chris Abell for fine tuning.

I have to take issue with Dave Abbe's suggesting if you have the tools to turn the mean time screws. Having the tools isn't enough. If you attempt to do this with the balance in the watch you will almost certainly be looking at a staff replacement and possible hairspring damage next. If you have the ability to remove the balance cock with the balance and hairspring and can safely work on it, fine...but if not please don't attempt this.

Roger, I must defer to your comments. When referring to "the tools" I did mean to imply the experience and the correct tools to remove the balance cock and wheel assembly, mount it in a watchmaker's pin and carefully hold the wheel while using a watchmaker's balance weight locking tweezers to rotate the mean time weights out 1/4 turn.
(Note, this pictorial view uses a 12s Elgin for demo only, most Elgins have no Mean time screws like the 4 that are probably used on Paul's Waltham).

Thanks for clarifying what you meant Dave. It's easy for us to assume certain things because we're so familiar with the procedures, but there are many folks reading these posts who are not familiar and your pictures and tutorials go a long way to help those folks understand.

quote:

watchmaker's balance weight locking tweezers (Dave Abbe message above)

Dear Dave,

I'm sure I would be able to manage the adjustment myself, thanks to your very clear instructions, except for those neat-looking locking tweezers which are not part of my arsenal. Would it be possible to use a screwdriver instead and what extra precaution is needed?

Paul

As Roger and Dave say the first thing you need to make sure is that the watch is good order throughout first and serviced otherwise you are just trying to mask other problems it needs to go on a timing machine and examined to see exactly what is wrong. Putting a stronger spring in just means you are driving it all harder which will throw it all out of adjustments you may find when the watch is serviced it will knock or other problems show up. Also there is a good chance a change in positional errors will occur. I am often asked just pop a mainspring in, or just replace a staff, unless the watch was recently serviced correctly it rarely works out well and you end up doing a full service to get good results.

quote:

Would it be possible to use a screwdriver instead and what extra precaution is needed?

Only the clamping type screw driver tweezers (below). A plain screwdriver can break the head off instead of adjusting the mean time screw. Then you have a REAL problem. I recommend Chris Abell first.