Roman bench vice?

[Medicus matt]

According to "Die Schraube zwischen Macht und Pracht", a catalogue about the roman use of threads from 1995, the romans were not able to cut "inner threads" into metal. Every metal screw mechanism that has been found has a pin serving as "inner thread".

What about the late period crossbow fibula? Some of them had screwed elements with reciprocating threads (see "A Late Antique Crossbow Fibula in The Metropolitan Museum of Art": Metropolitan Museum Journal, v. 35 (2000))