PartsTable TECHNICAL DATA SHEET
JULY 2026Technical Data Sheet

MS21231-5Bearing,plain,self-Aligning

Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M · NSN 3120-00-079-9974 · FSC 3120 · No Item Name Available
Verified by PartsTable
NSN 3120-00-079-9974 — this item is cataloged by the U.S. Government under National Stock Number 3120-00-079-9974. Primary manufacturer part number: MS21231-5.
Features
  • Bearing,plain,self-Aligning — FSC 3120
  • Bore Diameter: 0.3120 INCHES MINIMUM AND 0.3125 INCHES MAXIMUM IN
  • Outer Member Outside Diameter: 0.6870 INCHES MINIMUM AND 0.6875 INCHES MAXIMUM IN
  • Hardness Rating: 23.0 ROCKWELL C MINIMUM OUTER RACE MEMBER
  • Material: STEEL COMP 440C INNER MEMBER
  • Style Designator: WITHOUT INSERT OR LINER
  • Hardness Rating: 55.0 ROCKWELL C MINIMUM INNER MEMBER
  • Material: STEEL OUTER RACE MEMBER
Applications
  • Rotating machinery support and alignment
  • Shaft load distribution
  • Precision spindle assemblies
  • Applications requiring Steel Comp 440c Inner Member construction
General Description

The Bearing,plain,self-Aligning, cataloged under National Stock Number 3120-00-079-9974, is classified within Federal Supply Class 3120 (No Item Name Available) of the Bearings group. The primary manufacturer of record is Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M. Government technical data includes 10 verified specifications, sourced from the Federal Logistics Information System (FLIS). This item has 2 commercial cross-references from 2 manufacturers, enabling identification through both NSN and commercial part number lookups. 2 verified substitutes exist in the FLIS interchangeability database. Current acquisition status: Active.

Technical Specifications
ParameterValue
NSN3120-00-079-9974
Primary Part NumberMS21231-5
Item NameBearing,plain,self-Aligning
FSC / FSG3120 / 31 — No Item Name Available
ManufacturerMilitary Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M
StatusACTIVE
Bore Diameter0.3120 INCHES MINIMUM AND 0.3125 INCHES MAXIMUM IN
Outer Member Outside Diameter0.6870 INCHES MINIMUM AND 0.6875 INCHES MAXIMUM IN
Hardness Rating23.0 ROCKWELL C MINIMUM OUTER RACE MEMBER
MaterialSTEEL COMP 440C INNER MEMBER
Style DesignatorWITHOUT INSERT OR LINER
Hardness Rating55.0 ROCKWELL C MINIMUM INNER MEMBER
MaterialSTEEL OUTER RACE MEMBER
Outer Member Width0.3120 INCHES MINIMUM AND 0.3220 INCHES MAXIMUM IN
Inner Member Width0.4350 INCHES MINIMUM AND 0.4370 INCHES MAXIMUM IN
Static Radial Load Rating9400 POUNDS LBS
Lifecycle & Compliance
Acquisition StatusACTIVE
HAZMATNo
Verified Substitutes 2
3120-01-054-4693MS14102-5 INTERCHANGEABLE
Bearing,plain,self-Aligning
Sae International Dba Sae International
3120-01-364-3681KWDB16-7 INTERCHANGEABLE
Bearing,plain,self-Aligning
Sargent Aerospace & Defense, Llc Dba Kahr Bearings
Cross-Reference Index
Part NumberManufacturer
MS21231-5 Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M
MILB8942 Military Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M
Related Parts
3120-01-054-4693INTERCHANGEABLE
BEARING,PLAIN,SELF-ALIGNING
MS14102-5
3120-01-364-3681INTERCHANGEABLE
BEARING,PLAIN,SELF-ALIGNING
KWDB16-7

Frequently Asked Questions

What is NSN 3120-00-079-9974?

NSN 3120-00-079-9974 is a Bearing,plain,self-Aligning, manufactured by Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M, classified under FSC 3120 (No Item Name Available). Status: active.

What are the part numbers for NSN 3120-00-079-9974?

NSN 3120-00-079-9974 has 2 cross-referenced part numbers: MS21231-5 (Military Standards Promulgated by Military Departments Under Authority of Defense Standardization Manual 4120 3-M), MILB8942 (Military Specifications Promulgated by Military Departments/agencies Under Authority of Defense Standardization Manual 4120 3-M).

What NSN replaces 3120-00-079-9974?

There are 2 known substitutes for 3120-00-079-9974: 3120-01-054-4693, 3120-01-364-3681. Verify interchangeability with system specifications before substitution.

What are the specifications of MS21231-5?

Key specifications for MS21231-5: Bore Diameter: 0.3120 INCHES MINIMUM AND 0.3125 INCHES MAXIMUM IN; Outer Member Outside Diameter: 0.6870 INCHES MINIMUM AND 0.6875 INCHES MAXIMUM IN; Hardness Rating: 23.0 ROCKWELL C MINIMUM OUTER RACE MEMBER; Material: STEEL COMP 440C INNER MEMBER. 10 total characteristics are documented in the Federal Logistics Information System.

Validated with multiple authoritative sources, including Government, OEM, and Certified sources.
PartsTable Design LLC · partstable.com