ISO 9618:2016

Overview

ISO 9618:2016 is an international aerospace standard that specifies the dimensions of hexagonal, slotted (castellated), reduced-height nuts with MJ threads. It covers nuts of multiple strength/temperature classifications (450 MPa, 600 MPa, 900 MPa, 1 100 MPa and 1 250 MPa combined with corresponding maximum service temperatures) intended for use with split pins. The document provides configuration drawings, a dimension table (in millimetres) and tolerancing guidance for use in the compilation of aerospace product standards.

Key topics and technical requirements

• Configuration and dimensions: Detailed geometry for hexagon slotted (castellated) reduced-height nuts, shown in Figure 1 and Tabular data (Table 1). Dimensions and tolerances are expressed in millimetres.
• Thread system: MJ thread profiles and limit dimensions referenced to ISO 5855‑2.
• Strength/temperature classifications: Nuts are specified for classifications such as 450 MPa/120 °C, 450 MPa/235 °C, 600 MPa/425 °C, 900 MPa/235 °C, 900 MPa/315 °C, 900 MPa/650 °C, 1 100 MPa/235 °C, 1 100 MPa/730 °C and 1 250 MPa/600 °C. Notes clarify that the MPa value refers to minimum tensile stress at ambient temperature and the temperature value to the maximum temperature the nut can withstand without permanent alteration (surface treatment dependent).
• Compatibility with split pins: Intended for use with split pins conforming to ISO 1234; Table 1 gives thread/split‑pin diameter relationships.
• Form and position tolerances: Tolerances of form and position are to conform with ISO 8788.
• Surface treatment consideration: Dimensions apply after any surface coating(s) but before application of any lubricant.

Applications and users

• Aerospace designers and engineers specifying fasteners for airframes, engines and high-temperature components where weight, strength and locking via split pins are required.
• Fastener manufacturers producing MJ-thread castellated nuts to aerospace tolerances and coatings.
• Procurement and quality assurance teams verifying conformity of nuts to dimensional, thread and classification requirements.
• Maintenance and repair organizations (MROs) selecting replacement hardware compatible with split‑pin locking and approved fit/strength classes.

Practical uses include securing high-strength bolted joints where a castellated nut + split pin provides positive mechanical locking under vibration and thermal cycling.

Related standards

• ISO 1234 - Split pins (compatibility)
• ISO 5855‑2 - MJ threads - Limit dimensions for bolts and nuts
• ISO 8788 - Aerospace nuts - Tolerances of form and position

Keywords: ISO 9618:2016, aerospace nuts, castellated nuts, MJ threads, reduced height hexagon nut, dimensions, split pin, ISO 1234, fastener standard.