I want to order a case for a Bulova 10BZAC auto movement but all the cases shown are designated by Ligne size which is Greek to me....Can some shed some light on this.
Thank You
Well put and simple Geezer !!!!!
The standard measurement is called the Lancashire gage (an english system). With this system, the 0(zero) size movement, which measures 1 5/30 in diameter is used as the basic start point. Every 1/30 added in diameter increases the number size by 1; every 1/30 smaller lowers the number by 1 (expressed as a neg by size number over zero ie 3/0 is 3/30 in smaller than a 0 size. SO a 0 size watch is 1 5/30 in dia and a size 1 would be 1 6/30 in dia, a 10 size watch would be 1 15/30in dia.. From 0 down it goes 00 or 2/0 at 1 4/30, A smaller 3/0 size would be 1 3/30 in dia, a 4/0 would be 1 2/30 in dia etc etc. Math comes next to convert to a ligne size
1 in = 25.4 mm
1 mm=0.03937 in
1 ligne = 2.256 mm
The Ligne size is French ( thanks for complicating it even more frenchy !!!)
A little complicated but to figure in inches mm etc this is easiest for me to understand and requires only simple math to figure out sizes.
If you only need Ligne size, Geezer has it down simple, but many watches (pocket watches especially ) are number size not ligne and the above will convert back and forth with some ease, but if all you have is a movement or case and calipers, you can figure out all methods of size to get what you need.
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