Related Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
ASME B18.2.2 Lock Nuts Dimensions
Reduced-Height Inch-Series Hex Nuts for Vibration-Resistant Double-Nut Locking in Industrial and Structural Bolted Assemblies.
ASME B18.2.2 Lock Nuts — also widely referred to as hex jam nuts — are inch-series internally threaded fasteners with a reduced body height compared to a standard ASME B18.2.2 regular hex nut, specifically engineered to function as a locking element in double-nut configurations where the jam nut is tightened firmly against the face of a primary full-height nut to create a mechanically locked bolted joint that resists self-loosening under vibration, dynamic loading, and thermal cycling without the need for thread-locking adhesives, nylon inserts, or spring washers. The ASME B18.2.2 standard defines precise dimensional requirements for hex lock nuts (jam nuts) including the reduced width across flats, width across corners, reduced nut thickness, chamfer angle, and thread specifications for nominal sizes from 1/4 inch through 4 inches, maintaining the same across-flats dimension as the standard hex nut in each size but with a significantly reduced thickness that identifies them unambiguously as the jam nut in a double-nut assembly. When manufactured to ASTM A1082, the specification for high-strength stainless steel bolting material, ASME B18.2.2 Lock Nuts provide excellent corrosion resistance, non-magnetic performance, and reliable mechanical integrity in aggressive service environments including marine equipment, offshore structural connections, chemical processing plant machinery, food-grade production equipment, and coastal infrastructure where the combination of vibration loading and corrosive atmosphere would cause standard carbon steel jam nuts to corrode rapidly and lose their effectiveness as a locking element over time. The correct installation procedure for a double-nut locking system using ASME B18.2.2 lock nuts requires the jam nut to be applied first and set to a specified low torque, followed by the full hex nut tightened to full specified torque against the jam nut — this sequence correctly loads the thread flanks in opposing directions and locks the assembly. ASTM A1082 ASME B18.2.2 lock nuts are available with EN 10204 Type 3.1 material certification for all specification-controlled industrial procurement requirements.
ASME B18.2.2 Lock Nuts Dimensions (Inch)
| Nominal Size | Basic Major Diameter of Thread | Width Across Flats, F | Width Across Corners, G | Thickness, H1 | Runout, FIM | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| Basic | Min. | Max. | Min. | Max. | Basic | Min. | Max. | |||
| 1 1/8 | 1.1250 | 1 11/16 | 1.631 | 1.688 | 1.859 | 1.949 | 5/8 | 0.595 | 0.655 | 0.029 |
| 1 1/4 | 1.2500 | 1 7/8 | 1.812 | 1.875 | 2.066 | 2.165 | 3/4 | 0.718 | 0.782 | 0.032 |
| 1 3/8 | 1.3750 | 2 1/16 | 1.994 | 2.062 | 2.273 | 2.382 | 13/16 | 0.778 | 0.846 | 0.035 |
| 1 1/2 | 1.5000 | 2 1/4 | 2.175 | 2.250 | 2.480 | 2.598 | 7/8 | 0.839 | 0.911 | 0.039 |
Frequently Asked Questions
What stainless steel grades does ASTM A1082 cover for lock nuts?
ASTM A1082 covers duplex grades (S31803/2205, S32205/2205, S32750/2507, S32760/Zeron 100, S39277/AL-6XN) and precipitation-hardening grades (S17400/17-4 PH, S17700/17-7 PH, S15700/15-7 PH, S35500/AM-355) - all available for this product family at TorqBolt.
What is the standard dimensional reference for these lock nuts?
This product follows ASME B18.2 2, the dimensional standard for lock nuts in stainless steel. Material chemistry, mechanical properties and heat treatment follow ASTM A1082/A1082M. TorqBolt supplies both inch-series and metric sizes per the applicable ASME or ISO drawing.
Are A1082 lock nuts suitable for sour service (NACE MR0175)?
Yes, with hardness control. NACE MR0175 / ISO 15156 permits duplex grades S31803, S32205, S32750, S32760 at 28 HRC max for sour service. 17-4 PH (S17400) at H1150 condition (28 HRC) is the most common PH grade qualified for sour service. TorqBolt provides NACE-MR0175 compliant heat-treat reports.
What is the typical strength of A1082 super-duplex 2507 (S32750) lock nuts?
Super-duplex 2507 (S32750) per A1082: tensile 116 ksi (800 MPa) min, yield 80 ksi (550 MPa) min, elongation 15% min, 32 HRC max. PREN ≈ 42 - suitable for seawater, brine and chloride-rich pressure-vessel service. Higher strength than austenitic A193 B8M while offering pitting resistance well above 304/316.
References & Standards
- ASTM A1082 / A1082M - Standard Specification for High-Strength Precipitation-Hardening and Duplex Stainless Steel Bolting for Special-Purpose Applications (current edition 2016, active)
- ASTM A962 / A962M - General Requirements for Special-Purpose Bolting Materials
- ASTM A370 - Mechanical Testing of Steel Products
- NACE MR0175 / ISO 15156 - Sour-service hardness limits for petroleum & natural gas industries
- ASME B18 series - Dimensional standards for bolts, screws, nuts, studs
- ISO 4032 / 4033 / 4035 - Metric hexagon nut dimensional standards
Satisfaction Survey
