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ASME B18.2.4.1M Metric Hex Nuts – Dimensions, Specifications & Standards
Metric Hex Nuts for Reliable Metric Fastening Applications.
ASME B18.2.4.1M Metric Hex Nuts are metric-series internally threaded fasteners that provide the mating component for metric hex cap screws, metric hex bolts, and stud bolts in mechanical, structural, and process piping applications. Dimensional requirements govern width across flats, width across corners, nut height, thread pitch, and chamfer dimensions in SI metric units. The standard ensures compatibility with metric bolts per ASME B18.2.3.1M and B18.2.3.5M. In critical bolting assemblies, these nuts are paired with ASTM A1014/A1014M UNS N07718 (Inconel 718) stud bolts and cap screws for outstanding resistance to corrosion, galling, and stress relaxation at elevated temperatures. Also specified in ASTM A194 for general pressure and piping applications across carbon steel, alloy steel, and stainless steel grades. Proper nut-to-bolt grade matching is essential for safe bolted joint performance.
ASME B18.2.4.1M Metric Hex Nut Style 1 Dimensions (mm)
| Nominal Dia. | S | E | M | Dw | C | Total Runout of Bearing Surface FIM | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Width Across Flats | Width Across Corners | Thickness | Bearing Face Dia | Washer Face Thickness | ||||||
| Max. | Min. | Max. | Min. | Max. | Min. | Min. | Max. | Min. | Max. | |
| M1.6 | 3.20 | 3.02 | 3.70 | 3.41 | 1.30 | 1.05 | 2.3 | ... | ... | ... |
| M2 | 4.00 | 3.82 | 4.62 | 4.32 | 1.60 | 1.35 | 3.1 | ... | ... | ... |
| M2.5 | 5.00 | 4.82 | 5.77 | 5.45 | 2.00 | 1.75 | 4.1 | ... | ... | ... |
| M3 | 5.50 | 5.32 | 6.35 | 6.01 | 2.40 | 2.15 | 4.6 | ... | ... | ... |
| M3.5 | 6.00 | 5.82 | 6.93 | 6.58 | 2.80 | 2.55 | 5.1 | ... | ... | ... |
| M4 | 7.00 | 6.78 | 8.08 | 7.66 | 3.20 | 2.90 | 6.0 | ... | ... | ... |
| M5 | 8.00 | 7.78 | 9.24 | 8.79 | 4.70 | 4.40 | 7.0 | ... | ... | 0.30 |
| M6 | 10.00 | 9.78 | 11.55 | 11.05 | 5.20 | 4.90 | 8.9 | ... | ... | 0.33 |
| M8 | 13.00 | 12.73 | 15.01 | 14.38 | 6.80 | 6.44 | 11.6 | ... | ... | 0.36 |
| M10 | 15.00 | 14.73 | 17.32 | 16.64 | 9.10 | 8.70 | 13.6 | ... | ... | 0.39 |
| M10 | 16.00 | 15.73 | 18.45 | 17.77 | 8.40 | 8.04 | 14.6 | ... | ... | 0.39 |
| M12 | 18.00 | 17.73 | 20.78 | 20.03 | 10.80 | 10.37 | 16.6 | ... | ... | 0.42 |
| M14 | 21.00 | 20.67 | 24.25 | 23.35 | 12.80 | 12.10 | 19.4 | ... | ... | 0.45 |
| M16 | 24.00 | 23.67 | 27.71 | 26.75 | 14.80 | 14.10 | 22.4 | ... | ... | 0.48 |
| M20 | 30.00 | 29.16 | 34.64 | 32.95 | 18.00 | 16.90 | 27.9 | 0.8 | 0.4 | 0.56 |
| M24 | 36.00 | 35.00 | 41.57 | 39.55 | 21.50 | 20.20 | 32.5 | 0.8 | 0.4 | 0.64 |
| M30 | 46.00 | 45.00 | 53.12 | 50.85 | 25.60 | 24.30 | 42.5 | 0.8 | 0.4 | 0.76 |
| M36 | 55.00 | 53.80 | 63.51 | 60.79 | 31.00 | 29.40 | 50.8 | 0.8 | 0.4 | 0.89 |
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