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
High-strength socket head screws designed for compact and precision applications
B18.3 Socket Head Cap Screws Dimension Standard include precise socket and head specifications used in machinery and precision engineering.

| Nominal Size | Basic Screw Diameter | Body Diameter, D (mm) | Head Diameter, A (mm) | Head Height, H (mm) | Maximum Chamfer or Radius, C (mm) | Nominal Hexagon Socket Size, J | Socket Width Across Flats, J (mm) | Minimum Key Engagement, T (mm) | Minimum Wall Thickness, G (mm) | Maximum Chamfer or Radius, K (mm) | Fillet Juncture Diameter, F (mm) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Max. | Min. | Max. | Min. | Max. | Min. | Nom. | Dec. (mm) | Max. | Min. | Max. | Min. | ||||||
| #0 | 0.0600 | 1.524 | 1.443 | 2.438 | 2.311 | 1.524 | 1.448 | 0.102 | ... | 1.27 | 1.295 | 1.27 | 0.635 | 0.508 | 0.178 | 1.88 | 1.575 |
| #1 | 0.0730 | 1.854 | 1.765 | 2.997 | 2.845 | 1.854 | 1.778 | 0.127 | 1/16 | 1.575 | 1.613 | 1.588 | 0.787 | 0.635 | 0.178 | 2.21 | 1.905 |
| #2 | 0.0860 | 2.184 | 2.088 | 3.556 | 3.404 | 2.184 | 2.108 | 0.203 | 5/64 | 1.981 | 2.009 | 1.984 | 0.965 | 0.737 | 0.178 | 2.591 | 2.286 |
| #3 | 0.0990 | 2.515 | 2.41 | 4.089 | 3.912 | 2.515 | 2.413 | 0.203 | 5/64 | 1.981 | 2.009 | 1.984 | 1.118 | 0.864 | 0.178 | 2.921 | 2.591 |
| #4 | 0.1120 | 2.845 | 2.731 | 4.648 | 4.47 | 2.845 | 2.743 | 0.229 | 3/32 | 2.388 | 2.418 | 2.38 | 1.295 | 0.965 | 0.203 | 3.302 | 2.972 |
| #5 | 0.1250 | 3.175 | 3.053 | 5.207 | 5.029 | 3.175 | 3.073 | 0.305 | 3/32 | 2.388 | 2.418 | 2.38 | 1.448 | 1.092 | 0.203 | 3.683 | 3.353 |
| #6 | 0.1380 | 3.505 | 3.376 | 5.74 | 5.486 | 3.505 | 3.404 | 0.33 | 7/64 | 2.769 | 2.822 | 2.779 | 1.626 | 1.194 | 0.203 | 4.013 | 3.658 |
| #8 | 0.1640 | 4.166 | 4.026 | 6.858 | 6.528 | 4.166 | 4.039 | 0.356 | 9/64 | 3.581 | 3.622 | 3.571 | 1.956 | 1.422 | 0.203 | 4.775 | 4.369 |
| #10 | 0.1900 | 4.826 | 4.674 | 7.925 | 7.569 | 4.826 | 4.699 | 0.457 | 5/32 | 3.962 | 4.031 | 3.967 | 2.286 | 1.651 | 0.203 | 5.537 | 5.131 |
| #12 | 0.2160 | 5.486 | 5.321 | 8.23 | 7.976 | 5.486 | 5.334 | 0.559 | 5/32 | 3.962 | 4.031 | 3.967 | 2.616 | 2.083 | 0.254 | - | - |
| 1/4 | 0.2500 | 6.35 | 6.185 | 9.525 | 8.992 | 6.35 | 6.198 | 0.635 | 3/16 | 4.775 | 4.826 | 4.763 | 3.048 | 2.413 | 0.254 | 7.061 | 6.63 |
| 5/16 | 0.3125 | 7.938 | 7.755 | 11.913 | 11.328 | 7.925 | 7.772 | 0.838 | 1/4 | 6.35 | 6.426 | 6.35 | 3.835 | 3.023 | 0.254 | 8.814 | 8.357 |
| 3/8 | 0.3750 | 9.525 | 9.342 | 14.275 | 13.716 | 9.525 | 9.347 | 1.016 | 5/16 | 7.925 | 8.026 | 7.938 | 4.623 | 3.632 | 0.254 | 10.541 | 10.084 |
| 7/16 | 0.4375 | 11.113 | 10.907 | 16.662 | 16.027 | 11.125 | 10.922 | 1.194 | 3/8 | 9.525 | 9.627 | 9.525 | 5.41 | 4.216 | 0.381 | 12.294 | 11.811 |
| 1/2 | 0.5000 | 12.7 | 12.494 | 19.05 | 18.415 | 12.7 | 12.497 | 1.397 | 3/8 | 9.525 | 9.627 | 9.525 | 6.223 | 4.826 | 0.381 | 14.021 | 13.487 |
| 9/16 | 0.5625 | 14.288 | 14.067 | 21.412 | 21.006 | 14.275 | 14.072 | 1.575 | 7/16 | 11.1 | 11.227 | 11.113 | 7.01 | 5.436 | 0.381 | - | - |
| 5/8 | 0.6250 | 15.875 | 15.654 | 23.825 | 23.216 | 15.875 | 15.647 | 1.778 | 1/2 | 12.7 | 12.827 | 12.7 | 7.798 | 6.045 | 0.381 | 17.501 | 16.866 |
| 3/4 | 0.7500 | 19.05 | 18.811 | 28.575 | 27.788 | 19.05 | 18.796 | 2.159 | 5/8 | 15.875 | 16.027 | 15.875 | 9.398 | 7.239 | 0.381 | 21.031 | 20.32 |
| 7/8 | 0.8750 | 22.225 | 21.963 | 33.325 | 32.791 | 22.225 | 21.946 | 2.54 | 3/4 | 19.05 | 19.228 | 19.05 | 10.973 | 8.458 | 0.508 | 24.46 | 23.673 |
| 1 | 1.0000 | 25.4 | 25.11 | 38.1 | 37.49 | 25.4 | 25.095 | 2.896 | 3/4 | 19.05 | 19.228 | 19.05 | 12.573 | 9.652 | 0.508 | 27.94 | 27.127 |
| 1 1/8 | 1.1250 | 28.575 | 28.158 | 42.875 | 42.291 | 28.575 | 28.219 | 3.277 | 7/8 | 22.225 | 22.479 | 22.225 | 14.148 | 10.871 | 0.508 | 31.369 | 30.429 |
| 1 1/4 | 1.2500 | 31.75 | 31.333 | 47.625 | 47.041 | 31.75 | 31.394 | 3.658 | 7/8 | 22.225 | 22.479 | 22.225 | 15.748 | 12.065 | 0.508 | 34.798 | 33.858 |
| 1 3/8 | 1.3750 | 34.925 | 34.463 | 52.375 | 51.765 | 34.925 | 34.544 | 4.064 | 1 | 25.4 | 25.908 | 25.4 | 17.323 | 13.284 | 0.508 | 38.227 | 37.236 |
| 1 1/2 | 1.5000 | 38.1 | 37.638 | 57.15 | 56.49 | 38.1 | 37.719 | 4.47 | 1 | 25.4 | 25.908 | 25.4 | 18.923 | 14.478 | 0.508 | 41.656 | 40.665 |
| 1 3/4 | 1.7500 | 44.45 | 43.929 | 66.675 | 65.964 | 44.45 | 44.044 | 5.258 | 1 1/4 | 31.75 | 32.385 | 31.75 | 22.098 | 16.891 | 0.508 | 48.514 | 47.473 |
| 2 | 2.0000 | 50.8 | 50.241 | 76.2 | 75.438 | 50.8 | 50.368 | 6.045 | 1 1/2 | 38.1 | 38.862 | 38.1 | 25.273 | 19.304 | 0.508 | 55.372 | 54.051 |
| 2 1/4 | 2.2500 | 57.15 | 56.591 | 85.725 | 84.938 | 57.15 | 56.693 | 6.833 | 1 3/4 | 44.45 | 45.339 | 44.45 | 28.448 | 21.717 | 0.914 | 62.23 | 60.909 |
| 2 1/2 | 2.5000 | 63.5 | 62.896 | 95.25 | 94.412 | 63.5 | 63.017 | 7.62 | 1 3/4 | 44.45 | 45.339 | 44.45 | 31.623 | 24.13 | 0.914 | 69.088 | 67.615 |
| 2 3/4 | 2.7500 | 69.85 | 69.246 | 104.775 | 103.886 | 69.85 | 69.342 | 8.433 | 2 | 50.8 | 51.816 | 50.8 | 34.798 | 26.543 | 0.914 | 75.946 | 74.574 |
| 3 | 3.0000 | 76.2 | 75.596 | 114.3 | 113.386 | 76.2 | 75.667 | 9.195 | 2 1/4 | 57.15 | 58.293 | 57.15 | 37.973 | 28.956 | 0.914 | 82.804 | 81.432 |
| 3 1/4 | 3.2500 | 82.55 | 81.946 | 123.825 | 122.86 | 82.55 | 81.991 | 10.008 | 2 1/4 | 57.15 | 58.293 | 57.15 | 41.148 | 31.369 | 0.914 | 89.662 | 88.29 |
| 3 1/2 | 3.5000 | 88.9 | 88.296 | 133.35 | 132.359 | 88.9 | 88.341 | 10.82 | 2 3/4 | 69.85 | 71.247 | 69.85 | 44.323 | 33.782 | 0.914 | 96.52 | 95.148 |
| 3 3/4 | 3.7500 | 95.25 | 94.646 | 142.875 | 141.834 | 95.25 | 94.666 | 11.633 | 2 3/4 | 69.85 | 71.247 | 69.85 | 47.498 | 36.195 | 0.914 | 103.378 | 102.006 |
| 4 | 4.0000 | 101.6 | 100.996 | 152.4 | 151.333 | 101.6 | 100.99 | 12.421 | 3 | 76.2 | 77.724 | 76.2 | 50.673 | 38.608 | 0.914 | 110.236 | 108.864 |
| Nominal Length | Nominal Size, Tolerances on Lengths (mm) | |||
|---|---|---|---|---|
| 0 Through 9.525, Incl. |
11.112 Through 19.05, Incl. |
22.225 Through 38.1, Incl. |
Over 38.1 | |
| Up to 25.4, incl. | -0.762 | -0.762 | -1.27 | ... |
| Over 25.4 to 63.5, incl. | -1.016 | -1.524 | -2.54 | -4.572 |
| Over 63.5 to 152.4, incl. | -1.524 | -2.032 | -3.556 | -5.08 |
| Over 152.4 | -3.048 | -3.048 | -5.08 | -6.096 |