Bourgeaux

screw thread series

Also known as Bourgeaux & Delamure. In the 19^th century, a screw thread series used in Switzerland for manufacturing watches and clocks. It was realized in screw plates made by Martin, Perrelet et Martin, or Martin Fils. Plates marked “B” are the bourgeaux series. A “G” on the plate indicates left-hand threads.

The series had 26 sizes, from 00 to 24. We have no information on their thread form.

Compare Latard.

Number	Diameter in mm	Pitch in mm
24	0.213	0.086
23	0.267	0.088
22	0.291	0.091
21	0.312	0.093
20	0.344	0.094
19	0.376	0.096
18	0.414	0.101
17	0.452	0.111
16	0.496	0.120
15	0.563	0.133
14	0.640	0.150
13	0.713	0.159
12	0.782	0.167
11	0.858	0.181
10	0.936	0.200
9	1.008	0.219
8	1.097	0.239
7	1.203	0.261
6	1.299	0.271
5	1.404	0.274
4	1.523	0.289
3	1.641	0.298
2	1.797	0.320
1	1.984	0.359
0	2.169	0.388
00	2.363	0.420

Diameter and pitch data contributed by Job Visser.