A 5mm hex key socket with a 1/4in drive is an internal hex (Allen) socket designed to fit 5.00mm across flats fasteners and be driven by standard 1/4in (6.35mm) square drive ratchets, extensions or bit holders. Its primary use is to deliver firm, square engagement in recess hex-head bolts and screws where a ratchet or torque tool is preferred over a hand key for speed, access or controlled torque.

This socket is manufactured from chrome vanadium steel (Cr‑V) that has been heat treated for toughness and fatigue resistance and then chrome plated to provide a corrosion‑resistant, easy‑to‑clean surface. The face is machined to a precise 5mm internal hex profile and chamfered at the entry to aid fastener location and reduce burr damage. The socket accepts a 1/4in square drive on the back and is produced to DIN/ISO/BS tolerances for interchangeable hand tool sockets, ensuring accurate fit and repeatable engagement with metric hex fasteners.

Typical applications include automotive trim and dashboard work, bicycle maintenance, light engineering assembly, electrical and electronics enclosures and general building maintenance where metric Allen fasteners are used. The 1/4in drive size makes it particularly suited to confined spaces and detail work where a compact ratchet or extension is required, and it is commonly used by maintenance technicians, assemblers and workshop professionals across automotive, manufacturing, HVAC and trades sectors.

Key benefits are reliable corrosion resistance from the chrome finish, strength and wear resistance from the Cr‑V material and heat treatment, and compatibility with widely used 1/4in drive ratchets, extensions and torque tools for controlled tightening. The accurate internal hex profile reduces rounding of fastener corners and improves torque transfer compared with worn keys or improvised tools.

Duchy Fasteners holds 5mm hex key sockets in stock both as single pieces and as part of metric socket sets. Sizes and pack options include individual sockets for the 1/4in drive and multi‑piece metric sets typically covering 3mm–10mm, available in boxed or blister packaging to suit workshop and professional requirements.