Aquatimer accuracy

Is a gain of +3/4 seconds in a day within acceptable tolerance?

Also, out of interest is there any top tips for setting your watch precisely?

3-4 seconds a day is fine for a mechanical watch. I have a Casio watch that gets a signal from the Colorado atomic clock that I use to set my other watches, but the time on TV (cable or satellite) is also pretty accurate.

Bryce, IWC operating tolerance is 0 to +7 sec/day.

I use an atomic clock app on my iPhone and iPad which I check against my 140 year old regulator. The atomic clock app stacks up reasonably well against the regulator.

Hi Bryce,
To ensure that your minute hand is exactly on the minute marker as the second hand passes the 60 second marker follow these steps:
Pull out the crown when the second hand touches 60 to stop it.
Turn the minute hand Clockwise 10 minutes forward of the present time.
Turn the minute hand Anticlockwise to 1 minute in advance of your time signal.
Push in the crown when the time signal exactly matches that indicated on your dial.
This procedure eliminates the play between the motion work teeth which can be observed as a lag between the minute and second hands if the time is set with a clockwise motion only.
Your observed +3/4 sec/day is excellent timekeeping for a mechanical watch and is more accurate than most chronometer watches which have a huge tolerance of -4 to +6 seconds a day.
Leo

Thanks for that advice Leo, I for one didn't know about the clockwise/anti-clockwise interface.

Leo, my experince is only a little bit different: IWC uses 7750-s that really need to be set anti-clockwise by turning 10 minutes or so in the plus and then turning anti-clockwise but I do not have to turn exactly 1 minute over, my 3 7750-driven IWC-s need between 0 and 1 minute over-adjusting in the minus with an average of about 0.5 minutes. The role is that if you let the crown free after turning the hands, the minute hand goes a bit clockwise to its place. And if than it points to the wished place you arrived home. If not, you have to repeat the procedure. You usually need light fingers to do the job properly. Interestingly I experienced this on all my IWC 7750-s but not on other brands using the 7750. Once you learned the job, it is easy to live with it. Anyway, it does not bother me at all, with my oldest IWC 7750 (3706) almost 16 years in my possession.

Hi Roberto,
I didn't want to over-complicate my post by going through the circumstances and solutions where the setting method may be slightly different.
But, on reading your post, I realised that your experience will be common to many IWC owners.
The most likely reason for the slight uncertainty involved in achieving your 'wished place' is the strong spring in your screw-down crown which can slightly turn the stem/hands when the crown is pushed in, compressing the internal spring.
As you have seen with yours and most other modern IWC's this effect is very small, up to a minute. It can be very individual to each watch/owner due to the many variables involved. Owner dexterity, spring strength, age of crown seals, stem length + lubrication being a few.
On some examples of ladies MKXII and 3521 Ingenieur the hands could jump up to 4 minutes on pressing the crown due to the combination of fine movement and strong screw-in crown.

Leo, thx for your additions! I did not want to make my post overcomplicated, just as precise as possible, not to leave questions open.
The reason coming from outside the movement didn't come to my mind, though it seems quite logical. But I've never experienced the same at wifey's Mk.XII.Ladies (which I often forget as our IWC family member... :) ), not even after the gasket replacement, which would suggest again something that depends on the movement and we know that IWC used to modify the 7750-s on quite a few spots.
Anyway, there's no problem living with it. Hope there'll be a steel 7750 in the 2014 AT family too, just to have the 4th IWC with the same feature :)
(And hope that there'll be no He valve on that one...)
And sorry for stealing the thread to a certain extent.
Merry Xmas to you and to all our community here who celebrate Xmas!
Robert

It's interesting to me that my IWCs are the only watches I own that I need to move the minute hand forward, then back to the minute marker I wish it to be set on. I assume it has something to to do with the specs of how they wish these to be set up, but for the life of me, I can't figure out the necessity of this odd attribute. It can, at times, be a bit aggravating.

Only my Port Jubilee and my 5251 - both sharing the same movement DNA - avoid this need.

Does anyone know why? I have other ETA based watches that don't require this step.

Thanks

Terry