Running slow....

[p2n]

1 minute ago, JohnR725 said:

[if] there is a common cause

Which is going to be me

[rodabod]

The watch should run roughly to time without any oil.

40 minutes slow per day is a serious error, and assuming the balance is swinging with reasonable amplitude, I'd expect it to most likely be an issue with the resonance of the balance (hairspring, indexing, balance weight) or slipping in the motion works (cannon pinion). If you are sure that the timegrapher is set to the correct beat rate, then it would seem to point at the balance.

[rodabod]

200s slow per day is not massively slow. That's only three minutes, and probably within the range of the regulator if the hairsping has relatively few coils (since indexing makes a relatively bigger change to the hairspring length).

Bear in mind that often watches run slower once cleaned if they have previously been regulated when not running perfectly. For example, if the hairsping was slightly sticky when regulated previously, it would be regulated slow to compensate for the hairsping vibrating too fast due to stickiness.

[wheelnut]

Thought I'd add a point to this old thread about WD40

It's mostly diesel plus a light oil, plus an aromatic(fragrance).

The diesel is the penetrant and a short term lubricant but does evaporate away eventually.

The light oil lubricates and protects from corrosion but is only in a relatively small quantity so wears away in time.

The fragrance hides the diesel smell and gives it an acceptable aroma to the mechanic(sorry watchmaker ;-)).

[RichardHarris123]

On 3/22/2023 at 2:21 PM, wheelnut said:

Thought I'd add a point to this old thread about WD40

It's mostly diesel plus a light oil, plus an aromatic(fragrance).

The diesel is the penetrant and a short term lubricant but does evaporate away eventually.

The light oil lubricates and protects from corrosion but is only in a relatively small quantity so wears away in time.

The fragrance hides the diesel smell and gives it an acceptable aroma to the mechanic(sorry watchmaker ;-)).

 

[wheelnut]

ah, I stand corrected.