The 5010376 is a Pipistrel internal reference for an M4 button head Torx fastener manufactured to ISO 7380 (also commonly referred to as ISO 7380-1). This type of fastener is a metric machine screw with a low-profile rounded “button” head and a hexalobular (Torx) internal drive, designed for high torque transfer with reduced cam-out risk compared to standard hex socket screws.

In aviation applications such as those used by Pipistrel, these M4 Torx button bolts are typically used in lightweight structural assemblies, composite airframe panels, interior mounting points, avionics brackets, fairings, and access covers where a smooth aerodynamic surface and vibration resistance are required.

The M4 specification indicates a 4 mm nominal thread diameter with a standard 0.7 mm pitch. ISO 7380 defines the button head geometry, including a domed head with a relatively low profile, making it suitable where clearance and aerodynamics are important. The Torx drive (commonly T20 for M4) allows controlled tightening in production and maintenance environments, especially where repeatability and reduced tool wear are important.

In Pipistrel aircraft applications, such fasteners are usually selected in stainless steel (A2/A4), zinc-plated steel (class 8.8), or occasionally lightweight alloys depending on corrosion protection and weight requirements.

Key features include:

ISO 7380 M4 button head machine screw (Torx drive)
Thread size: M4 × 0.7 mm pitch (standard metric coarse thread)
Drive type: Internal Torx (typically T20 for M4)
Head style: Low-profile rounded button head for aerodynamic surfaces
Common materials: A2/A4 stainless steel or high-strength steel (8.8 class)
Designed for vibration-resistant aerospace and light aircraft assemblies
Suitable for composite-to-metal and sheet metal fastening applications
Higher torque capability compared to hex socket equivalents
Reduced cam-out risk during assembly and maintenance
Corrosion-resistant variants commonly used in aviation environments
Typical use: fairings, brackets, avionics mounting, interior structure panels