The primary goal of the standard is to achieve controlled material displacement. By strategically deforming the lip of the bearing's V-groove, the bearing becomes permanently locked into its housing, providing extreme axial retention without restricting the rotational freedom of the internal sphere or ball elements. NAS0331 Specification Document | PDF - Scribd
The document (often available as a ) provides detailed engineering requirements:
: Recommends dimensions, surface finishes, and chamfer requirements for the housing that receives the bearing.
Access to the official NAS0331 document is essential for compliance. The current active version is , revision published on July 31, 2020 . Superseded editions include NAS0331-1992 and NAS331:2013, which have been replaced by the 2020 revision.
standard, titled " Bearing Installation and Retention by Swaging or Staking nas0331 pdf
Aviation components encounter extreme vibrations, massive structural loads, and rapid thermal cycling. Standard press fits are insufficient to keep critical airframe bearings from migrating out of their housings. NAS0331 addresses this challenge by formalizing the cold-working deformation of metal to mechanically lock a bearing in place.
Originally established to standardize bearing retention across different manufacturers, the standard has undergone crucial updates to accommodate modern aerospace alloys and tight tolerance requirements. The current active version is .
(National Aerospace Standard) is a technical specification for heavy-duty, high-strength structural blind rivets
It applies specifically to bearings with a grooved outer race and covers various structural housing materials. Key Techniques Covered: The primary goal of the standard is to
: Technicians reference the standard for proper bearing removal and replacement using specialized tooling.
| NAS Standard | Focus Area | | :--- | :--- | | | Bearing Installation & Retention | | NAS1330 | High-strength countersunk head fasteners | | NAS4000 series | Composite materials and processes | | NAS5000 series | Hydraulic systems components |
Offers the NAS 0331 Rev.2 document with multi-user access options.
Specifications for balls and outer rings made of specific alloys. Access to the official NAS0331 document is essential
Incorrect installation can lead to bearing binding or uneven wear, reducing the component's lifespan.
Standards for no-load torque values and internal radial play measurements.
Swaging employs a rotary motion, typically via a drill press or specialized tri-roller tool, to gradually roll the bearing's v-groove into place, forming a secure fit. Portable versions of these tools allow for on-site repairs and are often used for on-wing bearing retention and replacement in constrained spaces.
The standard categorizes different mechanical retention techniques into "Methods," with Method 100 and Method 200 being the most common in aerospace MRO (Maintenance, Repair, and Overhaul). 1. Bearing Staking (Method 100)
The is the premier technical specification governing bearing installation and retention by swaging or staking across the global aerospace and defense sectors. Originally published by the Aerospace Industries Association (AIA) / National Aerospace Standards (NAS) , this protocol establishes critical benchmarks for component mechanical retention, preventing component push-out under high vibration and heavy flight stresses.
