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Discussion in 'European & Other Pocket Watches' started by John Matthews, Dec 2, 2018.
looking really good, I always liked this one, lovely balance cock
Looking back through this thread I noticed the observation of yours regarding the barrel arbor.
Almost all fusee movements will be found to have similar marks, which I believe relate to the initial setup of the barrel in the plates; the small cut or pip in the end of the arbor and a matching mark on the plate next to it would have marked the position of the arbor when the correct amount of pre-tension had been applied, the extent of which would properly have been established with a fusee adjusting rod, (see DP's archive for examples). Following a service, the marks would allow the barrel setup to be restored fairly accurately to its previous state without having to test it again.
Of course, replacing the mainspring would require a fresh use of the adjusting rod and a new mark on the plate, and that's partly how yours has acquired five pips and at least one linear mark, although I doubt if it's had five new springs from new!
Hi Graham - I understand the use of the marks on the arbor and the plate, but I don't understand how the adjusting rod was used.
I found examples on David's site. So here's a clip from Google search that brings up David's photographs which I hope David would not mind me using - a search on his site will bring up the high resolution versions ...
The first two are of the same rod, described as watch size, the third Lancashire pattern watch size and the final one David describes as rare chronometer size. David references Crom Horological Shop Tools and Thomas Martin's Circle of Mechanical Arts. The former is available at £100+, but the latter I have just discovered an ebook, that is currently downloading.
Here is the diagram of the adjusting rod shown as fig 20 in Martin ...
and here is the description ...
So there we have it - all that is required is to read and understand - which I have yet to do ...
Okay - I have now read and I believe I understand.
A worthwhile read and an education as to importance placed on the attention to detail and the iterative nature of the process to achieve a correctly profiled fusee to achieve good timekeeping.
Graham - the description appear to place the emphasis on using the rod to adjust the profile of the fusee more than adjusting the barrel - do you agree?
Yes, I do agree, Martin is clearly more concerned with the making of the watch, and when he was writing, I'm guessing that this method of matching the fusee to the spring was a practical necessity for craftsmen, who mostly wouldn't have had the time, knowledge or inclination to do the maths, even though Hooke had laid the foundations for it many years before. However, the adjustment of the degree of mainspring setup when it needed replacing was a useful secondary function.