ASTM A194 Grade 2H Nut Dimensions — ASME B18.2.2 Heavy Hex
ASTM A194 Grade 2H heavy hex nuts are manufactured per ASME B18.2.2 dimensional standard. This page covers width across flats, thickness, sizes, and thread series for inch-series 2H nuts used in high-pressure/high-temperature bolting.
ASME B18.2.2 Heavy Hex Nut Dimensions (Inch Series)
| Nominal Size | Width Across Flats F (in) | Thickness H (in) | Thread |
|---|---|---|---|
| 1/4 | 1/2 | 15/64 | 1/4-20 UNC |
| 5/16 | 9/16 | 19/64 | 5/16-18 UNC |
| 3/8 | 11/16 | 23/64 | 3/8-16 UNC |
| 1/2 | 7/8 | 31/64 | 1/2-13 UNC |
| 5/8 | 1-1/16 | 39/64 | 5/8-11 UNC |
| 3/4 | 1-1/4 | 47/64 | 3/4-10 UNC |
| 7/8 | 1-7/16 | 55/64 | 7/8-9 UNC |
| 1 | 1-5/8 | 63/64 | 1-8 UN |
| 1-1/8 | 1-13/16 | 1-7/64 | 1-1/8-8 UN |
| 1-1/4 | 2 | 1-7/32 | 1-1/4-8 UN |
| 1-3/8 | 2-3/16 | 1-11/32 | 1-3/8-8 UN |
| 1-1/2 | 2-3/8 | 1-15/32 | 1-1/2-8 UN |
| 1-3/4 | 2-3/4 | 1-23/32 | 1-3/4-8 UN |
| 2 | 3-1/8 | 1-31/32 | 2-8 UN |
| 2-1/4 | 3-1/2 | 2-13/64 | 2-1/4-8 UN |
| 2-1/2 | 3-7/8 | 2-29/64 | 2-1/2-8 UN |
| 2-3/4 | 4-1/4 | 2-45/64 | 2-3/4-8 UN |
| 3 | 4-5/8 | 2-61/64 | 3-8 UN |
| 3-1/4 | 5 | 3-3/16 | 3-1/4-8 UN |
| 3-1/2 | 5-3/8 | 3-7/16 | 3-1/2-8 UN |
| 3-3/4 | 5-3/4 | 3-11/16 | 3-3/4-8 UN |
| 4 | 6-1/8 | 3-15/16 | 4-8 UN |
Mechanical Properties
| Property | Value |
|---|---|
| Material | Carbon Steel Q&T (UNS K04100) |
| Hardness | 248-352 HBW (24-38 HRC) |
| Proof Load (1-inch 8UN) | 140,000 lbf min |
| Temperature Range | up to 800°F (427°C) |
Thread Series
ASTM A194 Grade 2H heavy hex nuts use:
- UNC (Unified Coarse): 1/4 through 7/8 inch sizes
- 8UN (8-thread Series): 1 inch and larger — matches A193 stud bolt threading
- Class 2B fit per ASME B1.1
Related Pages
For full A194 Grade 2H specification including chemistry, marking, and inspection: Grade 2H product page · ASME B18.2.2 heavy hex hub · ASTM A194 PDF · A194 hub.