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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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