The M5 x 75mm Spline 10mm Insert Bit is a specialist drive bit intended for installing and removing M5 spline-head fasteners where a 10mm spline recess is used. Its primary use is to provide a precise, durable engagement between drive tool and fastener in applications requiring a non-standard internal spline drive rather than Phillips, Pozidriv or hexagon sockets.

This insert bit is manufactured from S2 tool steel and heat treated to a hardness typically in the 58–62 HRC range to resist tip wear. The bit has a 75mm usable length to give extra reach into recessed or awkward positions and a 10mm spline tip sized to match spline recess heads. The shank is a 1/4in (6.35mm) hex for compatibility with standard quick-change holders and cordless drivers; the shank conforms to common bit shank dimensions (DIN 3126 / ISO 1173) to fit modern chucks and bit sockets. It is finished with a black phosphate coating to give improved corrosion resistance and reduced surface glare during assembly work.

The product is designed to work with M5 metric fasteners (M5 x 0.8 coarse pitch, per ISO metric thread specifications ISO 261/965) fitted with internal spline heads. Typical industries and applications include automotive repair and restoration, industrial machinery maintenance, HVAC and refrigeration assemblies, security fixings, metal fabrication and marine installations where spline-headed screws are used for tamper resistance or torque transmission advantages.

Key benefits include positive bit-to-screw engagement that reduces cam-out and damage to spline recesses, the toughness and wear resistance of S2 tool steel for extended service life, and the corrosion protection offered by the phosphate finish for use in workshop and field environments. The 75mm length provides access to recessed fasteners while the 1/4in hex shank ensures broad compatibility with power drivers and manual bit handles.

Duchy Fasteners stocks this Spline 10mm insert bit in a range of lengths and sales options; available sizes and pack quantities include singles and multi-packs to suit workshop and trade requirements. If you need alternative spline sizes or complementary drive bits, please contact our sales team.