Thury Thread

The Thury Thread is a historical thread developed towards the end of the 19th century specifically for the needs of the Swiss watch industry. The creator and namesake of the thread standard is Swiss botanist Marc Thury, who was involved in developing and manufacturing scientific instruments and co-founded the "Société genevoise d'instruments de physique" (SIP), still active today in precision machining.

The Thury Thread was popular after its introduction in 1878 but was hindered internationally by the British Science Association, which favored the imperial Whitworth thread over the metric Thury Thread. However, the committee, including Joseph Whitworth, recognized the excellent design of the Thury Thread, and soon after, the British Association Thread (BA) was introduced, closely resembling the Thury Thread with minimal deviations.

In the Swiss watch industry, the Thury Thread, also known as Filière Suisse (FS), was widespread for decades but always overshadowed by the more influential BA Thread. Eventually, both thread types were almost completely replaced by the metric ISO thread and are now rarely used.

The Thury Thread is a metric thread, with external diameter and pitch in mm. The flank angle is 47.5°, chosen to ease thread manufacturing and provide greater holding strength than larger angles.

Thread numbering replaces the designation in the Thury Thread, ranging from 0 to 25, totaling 26 defined thread sizes. The table below for the Thury Thread includes external diameter and pitch information, as well as the appropriate core hole diameters required for cutting a Thury Thread.