ISO 13921-2008 PDF

Full title and description

ISO 13921:2008 — Aerospace — Screws, 100° reduced countersunk head, internal offset cruciform ribbed or unribbed drive, normal shank, short or medium length MJ threads, metallic material, coated or uncoated, strength classes less than or equal to 1 100 MPa — Dimensions. This International Standard specifies dimensional and form characteristics for this specific type of aerospace screw to ensure interchangeability and suitability for aerospace product standards.

Abstract

ISO 13921:2008 defines the dimensions and related dimensional tolerances for 100° reduced countersunk head screws with an internal offset cruciform (ribbed or unribbed) drive, normal shank and short or medium MJ threads, intended for metallic (coated or uncoated) materials and strength classes up to 1 100 MPa. It is intended for use in the compilation of aerospace product standards.

General information

• Status: Published (confirmed).
• Publication date: 2008-08 (August 2008).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 49.030.20 (Aerospace engineering; fasteners/fastening).
• Edition / version: Edition 2 (2008).
• Number of pages: 5.

Key bibliographic and lifecycle details (status, edition, publication month/year, ICS and page count) are recorded on ISO's catalogue entry for the standard.

Scope

Specifies the dimensional characteristics (head geometry, drive type, shank tolerance categories and MJ thread length categories) for 100° reduced countersunk-head screws with an internal offset cruciform drive used in aerospace applications. The standard applies when compiling aerospace product standards that require these screw types and dimensional specifications.

Key topics and requirements

• Defined head geometry: 100° reduced countersunk head dimensions and tolerances.
• Drive specification: internal offset cruciform, ribbed or unribbed.
• Shank and thread classification: normal shank with close or large tolerance; short or medium length MJ threads.
• Material and surface condition: metallic screws, coated or uncoated, and applicability up to specified strength classes (≤ 1 100 MPa as stated in the standard).
• Dimensional tolerances and limits necessary to ensure interchangeability in aerospace assemblies.
• Use as a normative dimensional reference for aerospace product standards and related procurement/specification documents.

Typical use and users

Used by aerospace engineers, fastener designers and manufacturers, procurement and quality departments, technical authors of aerospace product standards, and conformity assessors who need a dimensional reference for this specific screw type to ensure interchangeability, fit and mechanical compatibility in aerospace assemblies.

Related standards

Previous edition: ISO 13921:1996 (withdrawn). The standard is maintained under ISO/TC 20/SC 4 (aerospace fasteners and associated hardware); users often refer to other aerospace fastener standards and general screw/fastener dimension standards when specifying assemblies.

Keywords

countersunk head screw; 100° reduced countersunk; internal offset cruciform drive; ribbed drive; MJ thread; aerospace fasteners; screw dimensions; dimensional tolerances; strength class; ISO 13921.

FAQ

Q: What is this standard?

A: ISO 13921:2008 is an International Standard that specifies dimensional requirements for a particular aerospace screw type (100° reduced countersunk head with internal offset cruciform drive) to ensure consistent dimensions and interchangeability.

Q: What does it cover?

A: It covers head and drive geometry, shank tolerance categories, MJ thread length categories (short/medium), material/coating applicability and the dimensional tolerances needed for aerospace usage.

Q: Who typically uses it?

A: Aerospace designers and engineers, fastener manufacturers, procurement and quality assurance personnel, and standards authors who need a dimensional reference for specifying or verifying these screws in aerospace products.

Q: Is it current or superseded?

A: ISO 13921:2008 is the second edition (published August 2008) and was reviewed and confirmed by ISO (the catalogue entry shows confirmation during routine review), so the 2008 edition remains the current published version.

Q: Is it part of a series?

A: It is a standalone ISO standard addressing a specific screw type but sits within the broader portfolio of aerospace fastener standards maintained by ISO/TC 20/SC 4. The standard replaced the 1996 edition.

Q: What are the key keywords?

A: countersunk head screw, 100° reduced countersunk, internal offset cruciform, MJ threads, aerospace fasteners, dimensions, tolerances, strength class.