Overview
The Lawson A21129 is a premium Tru-Torq® Grade 9 hex cap screw engineered for demanding industrial applications requiring ultra-high tensile strength. This 7/8-9 x 7″ fastener delivers minimum 180,000 PSI tensile strength, exceeding SAE J429, ASTM, and Military Grade 8 specifications. The matched-component design ensures compatibility with Lawson’s full range of Tru-Torq nuts, washers, and lock nuts for complete system reliability.
Key Features
- Ultra-High Strength: 20% stronger than standard Grade 8 fasteners with 180K PSI minimum tensile strength
- Fatigue & Vibration Resistance: UNJ thread design reduces stress concentration and resists loosening under cyclic loads
- Enhanced Wrenching Safety: 20% higher-than-normal wrenching surface distributes torque forces evenly and reduces fastener failure risk
- Superior Corrosion Protection: Perma-Plated zinc finish for extended service life in demanding environments
- Traceability & Identification: Proprietary head marking and diameter identification for easy part tracking and assembly verification
- Precision Manufacturing: Heat-treated, quenched, and tempered alloy steel with increased chamfer for smooth assembly
Technical Specifications
The following specifications define this fastener for critical maintenance and replacement applications:
- Size: 7/8-9 x 7″
- Grade: 9 (Alloy Steel)
- Tensile Strength: Minimum 180,000 PSI
- Thread Type: Coarse (UNJ), fatigue-resistant
- Finish: Zinc (Perma-Plated for corrosion resistance)
- Head Style: Hex cap (full hex)
- Head Height: 21/32″
- Across Flats: 1-5/16″
- Material: Alloy Steel
- Standard Compliance: Exceeds SAE J429, ASTM, and Military Grade 8 requirements
Typical Applications
The Lawson A21129 is specified for industries and systems requiring matched, high-strength fastening:
- Heavy equipment and machinery assembly
- Structural connections in demanding industrial environments
- Vibration-prone applications where bolt loosening cannot be tolerated
- Critical maintenance and repair where Grade 8 equivalents are insufficient
- Aerospace, automotive, and defense sector fastening
- Equipment requiring long service life under high stress
Compatibility & Replacements
Compatible With
- Lawson Tru-Torq Grade 9 hex nuts and lock nuts (matched strength)
- Lawson Tru-Torq flat washers and lock washers
- Industrial equipment requiring 180K PSI or higher tensile strength fasteners
- SAE J429 Grade 8 replacement applications (exceeds Grade 8 specs)
- Systems requiring UNJ thread design for fatigue resistance
Replaces / Drop-In Replacement For
Verify compatibility with your system integrator before ordering. This fastener may replace comparable Grade 8 hex cap screws of the same size, but always confirm specifications with your equipment manufacturer or engineering team.
Works With
- SAE J429 Grade 8 equivalent systems
- ASTM A354 Grade BC fastening specifications
- Military fastening standards (MIL-SPEC compliant)
- Matched Lawson Tru-Torq component systems
- Standard hex key tools and torque wrenches
