☙

Progress screw thread

A thread series used in watchmaking in Switzerland, 19ᵗʰ – 20ᵗʰ centuries. According to de Carle, “the most popular modern Swiss screw thread.” As is obvious from the table below, the size number is the diameter in tenths of a millimeter. Thread angle, 50 degrees; depth of thread, 0.8 pitch. Depth of rounding, 0.093 × pitch; radius, 0.0732 × pitch.

The company sold ready-made screws, and issued a screw plate as a means of checking sizes. Much of the use of the series occurred when makers found it convenient to thread their own screws using the screwplate as a die.

Number	Diameter, millimeters	Pitch, millimeters
4	0.40	0.100
4½	0.45	0.100
5	0.50	0.125
5½	0.55	0.125
6	0.60	0.150
6½	0.65	0.150
7	0.70	0.175
7½	0.75	0.175
8	0.80	0.200
8½	0.85	0.200
9	0.90	0.225
9½	0.95	0.225
10	1.00	0.250
11	1.10	0.275
12	1.20	0.300
13	1.30	0.325
14	1.40	0.350
15	1.50	0.375
16	1.60	0.32 or 0.457
17	1.70	0.34 or 0.486
18	1.80	0.36 or 0.514
19	1.90	0.38 or 0.543
20	2.00	0.40 or 0.571

Sorry. No information on contributors is available for this page.