ISO 3202:1997

Overview

ISO 3202:1997 defines the dimensional requirements for a specific family of aerospace screws: pan head, internal offset cruciform (ribbed or unribbed) drive, threaded to the head, using MJ threads, made of metallic material, coated or uncoated, and with strength classes ≤ 1 100 MPa. Published by ISO/TC 20 (Aircraft and space vehicles) SC4, this second edition standardizes form, dimensions and selection criteria used in aerospace product standards and procurement.

Key topics and technical requirements

• Scope and intent: Specifies dimensions and tolerances (in millimetres) for pan head screws with internal offset cruciform drives, intended for aerospace fastener systems.
• Drive and thread system: Uses MJ thread designation and internal offset cruciform drives (ribbed or unribbed). Drive profiles reference related drive standards.
• Dimensional detail: Includes a figure and a tabulated set of dimensional data for drive and thread codes (MJ1 through MJ12), plus guidance on edge breaks (0.1–0.4 mm).
• Tolerancing & form: Tolerances of form and position are handled by ISO 7913; dimensions apply after any surface coating but before application of lubricants.
• Lead and runout: Lead and runout requirements are addressed for threaded-to-head screws, ensuring consistency in thread start/finish and functional engagement.
• Length increments: Standardizes available screw lengths (increments: 2 mm for L < 100 mm; 4 mm for L ≥ 100 mm), with guidance for selecting greater lengths.
• Applicable materials and finishes: Covers metallic materials, coated or uncoated, within the stated strength classes (≤ 1 100 MPa).

Applications and users

ISO 3202 is essential for:

• Aerospace designers and mechanical engineers specifying fasteners for airframes, interiors, and avionics mounts.
• Fastener manufacturers producing pan head, offset cruciform screws to aerospace tolerances.
• Quality assurance and inspection teams verifying dimensions, lead/runout and form tolerances during production and incoming inspection.
• Procurement and supply chain professionals ensuring purchased screws meet aerospace standardization and interchangeability requirements.

Practical benefits include improved interchangeability, reduced assembly issues from improper drives or runout, and consistent selection of coated/uncoated fasteners with known strength limits.

Related standards

Key referenced standards include:

• ISO 5855-2 - MJ threads limit dimensions for bolts and nuts
• ISO 7913 - Tolerances of form and position (metric)
• ISO 3353 - Rolled threads for bolts
• ISO 14275 / ISO 14276 - Internal offset cruciform drives (metric series)

Keywords: ISO 3202, aerospace screws, pan head screws, MJ threads, offset cruciform drive, screw dimensions, aerospace fasteners, strength classes 1100 MPa.