Löwenherz thread

A screw thread system devised by a commission of instrument makers, government agencies and technical societies, and introduced in Berlin in 1894. In 1888 the Verein Deutscher Ingenieure had introduced a thread series covering diameters from 6 millimeters to 40 millimeters. The new series adopted the same thread form but extended it down to 1 mm; the 6 - 10 mm sizes are identical to the earlier series. It was used in instruments made in Germany and Austria and to some extent France in the late 19th – early 20th century.

The system is named for Dr. Leopold Löwenherz, a physicist active in metrology and especially the design of instruments, who was Director of the Physikalisch-Technische-Reichsanstalt. The designation Löwenherz thread has for a long time been applied to the whole series, not just the 1 mm to 10 mm portion.

Dimensioned drawing of the thread in cross section

All dimensions in millimeters.
Diameter Pitch Root
Diameter
Pitch
diameter
Tap
drill
1.0 0.25 0.625 0.812 0.64
1.2 0.25 0.825 1.012 0.84
1.4 0.30 0.950 1.175 0.97
1.7 0.35 1.175 1.437 1.20
2.0 0.40 1.400 1.700 1.44
2.3 0.40 1.700 2.000 1.74
2.6 0.45 1.925 2.260 1.97
3.0 0.50 2.250 2.620 2.30
3.5 0.60 2.600 3.050 2.65
4.0 0.70 2.950 3.470 3.00
4.5 0.75 3.375 3.930 3.43
5.0 0.80 3.800 4.400 3.87
5.5 0.90 4.150 4.825 4.23
6.0 1.00 4.500 5.250 4.60
7.0 1.10 5.350 6.175 5.45
8.0 1.20 6.200 7.100 6.30
9.0 1.30 7.050 8.025 7.15
10 1.40 7.900 8.954 8.00
12 1.60 9.600 10.800 9.70
14 1.80 11.300 12.650 11.40
16 2.00 13.000 14.500 13.10
18 2.20 14.700 16.350 14.82
20 2.40 16.400 18.200 16.52
22 2.80 17.800 19.900 17.93
24 2.80 19.800 21.900 19.93
26 3.20 21.200 23.600 21.35
28 3.20 23.200 25.600 23.35
30 3.60 24.600 27.300 24.75
32 3.60      
36 4.00      
40 4.40      
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