The NAS561P4-10 is a National Aerospace Standard slotted spring pin (roll pin) used for vibration-resistant mechanical retention, alignment, and hinge/shaft locking in aircraft structures and mechanical assemblies. It is designed to be driven into a drilled hole where it compresses inward and applies constant spring force against the hole wall.

This specific variant corresponds to the NAS561P4 series with nominal dimensions of 1/8" diameter and 5/8" length, making it a shorter version of the NAS561P4-18 you provided earlier. It is commonly used where compact retention is required without adding threaded fasteners or additional locking hardware.

The slotted tubular design provides controlled elastic deformation, ensuring strong frictional retention while allowing service removal and replacement during maintenance.

Key features include:

NAS561 series aerospace slotted spring pin (roll pin)
Size: 1/8" diameter × 5/8" length (short variant)
Supplied in bulk pack (25 pcs) for maintenance and assembly use
Self-retaining spring steel construction (no threads required)
High resistance to vibration loosening in aircraft environments
Typically made from hardened carbon or alloy spring steel (1070–1095 range)
Corrosion-protected finish depending on supplier (zinc / cadmium / phosphate)
Used for alignment, hinge retention, and mechanical locking applications
Lightweight, low-cost aerospace standard fastening element
Conforms to NAS561 specification used in aviation and military systems
Suitable for repeated maintenance replacement in airframe assemblies
Compatible with MS16562-series equivalent roll pins