Viti di fermo con intaglio et cupola conica DIN 551 / ISO 4766-PA 6.6 M4 x 25

Slotted screw drives are the oldest form of rotary drives for fastening screws. The Schltz is usually manufactured in a pressed or milled version. Because of its uneconomical processing method (slow, unwieldy), the slot is increasingly disappearing in favor of other drives (hexagon socket, cross slot, hexagon socket).

Plastics differ from polymers due to the addition of additives. Typical additives include plasticisers, stabilisers, colourants, fillers and reinforcing agents. Plastics can be classified according to various criteria, e.g. molecular synthesis, molecular structure, chemical origin or, based on their mechanical and thermal behaviour, into the three main groups: thermoplastics, thermosets and elastomers.

Polyamide 6.6 is a thermoplastic and therefore has long, thread-like macromolecules that have no cross-linking points. PA 6.6 is milky white, has a smooth and abrasion-resistant surface, is resistant to chemicals and solvents and is hard and tough. Various standards, such as DIN EN 34810, DIN 34811, DIN 34812, DIN 34813, DIN 34814, DIN 34815 and DIN 34816, regulate the properties of mechanical fasteners made of plastics (screws, nuts, washers).