Siemens & Halske - Thread
The Siemens & Halske thread is an old type of thread developed around 1900, primarily used for telegraphs and later for telephones. Therefore, the Siemens & Halske thread is also known as telegraph thread, postal thread, or mechanic's standard thread. The abbreviation S&H thread is also common.
The Siemens & Halske thread is no longer used today. However, when repairing and restoring historical telephones, you may still encounter S&H screws. In such cases, you can have corresponding taps and dies custom-made. Contact us anytime with your request!
The Siemens & Halske thread is a metric thread, so all dimensions are given in mm. The flank angle of the telegraph thread is a unique feature, as it is not constant but assigned a specific angle α for each thread size. The values for the flank angle range between 50° and 68°.
The Siemens & Halske threads do not have a thread designation but a thread numbering. Each number corresponds to a fixed combination of external diameter, pitch, and flank angle. The numbering ranges from 11 to 36 with irregular intervals between the numerical values.
The thread table for the Siemens & Halske thread comprises twelve entries. Besides the external diameter, pitch, and flank angle, the core hole diameter required for threading is also listed. Particularly noteworthy in the Siemens & Halske thread table is the constantly changing flank angle.