Wednesday, 16 November 2016

More on magnetism and watches.

Waltham 1899-Vanguard, 19J, 1902.
(click for a larger view)
A while ago I wrote about how magnetic fields can affect a watch movement, in particular how the coils of the hairspring could end up sticking to each other. This post is about something a bit different.

The Waltham 1899-Vanguard shown here came in barely running (although it was described as "in "good working order") after cleaning, a new mainspring and fixing a number of issues, including replacing a winding pinion that came from a 1908 model that is not compatible with the 1899 and which was causing winding problems, the movement was running with an excellent amplitude (swing of the balance) of 320 degrees.

However when it was put in the case this dropped to an unacceptable 200 degrees and the timekeeping went haywire. When this happens it is normally due to problems caused by compression or distortion of the movement in some way after tightening the case screws, either because of a fault in the movement or by some distortion in the watch case forcing part of the movement parts out of true or causing something to rub. After extensive investigation I could not find anything wrong.

Some degaussing equipment (Demagnetizers) shown on
the Cousinsuk.com web site.
I put the movement in a different watch case and it was fine so I got out the magnetic compass which went wild around the case and the problem was found.

Normally there is a trivial amount of ferrous material in a gold, filled gold or silver watch case, but this is a Hunter, and so it has two large and powerful steel springs in it to flip open the lid and to hold the lid closed. These had clearly become strongly magnetized at some point and that was causing the problem.

A few goes with the degaussing machine and all was resolved.

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