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
0.45 0.100
5 0.50 0.125
0.55 0.125
6 0.60 0.150
0.65 0.150
7 0.70 0.175
0.75 0.175
8 0.80 0.200
0.85 0.200
9 0.90 0.225
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

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