Property Class 12.9 Steel Hex Head Cap Screws, UNC combine the dimensional form of ASME B18.2.1 with the material properties of grade ISO 898-1 property class 12.9: requires plating or black-oxide protection, magnetic, service range commonly limited to approx. +300 °C; confirm against the coating and the load. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.
Why Choose Property Class 12.9 Steel for Hex Head Cap Screws, UNC
The highest common strength class, for high-load machine assembly. For hex head cap screws, unc, this matters when requires plating or black-oxide protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 12.9 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
| Corrosion characteristic | Requires plating or black-oxide protection |
Galvanic & Galling Considerations
For hex head cap screws, unc in steel, the dominant compatibility issue is hydrogen embrittlement at high property classes (10.9 and above) when electroplated. Plating must be followed by an appropriate baking treatment, or a non-electroplated finish (mechanical zinc, zinc flake) should be substituted.
Comparable Grades
For Hex Head Cap Screws, UNC, class 8.8 is the comparable strength step. Move up when the joint preload approaches the proof load of the current class; move down when the joint is over-specified. For corrosion-critical service, switch to stainless A2 or A4.
Sizes of Hex Head Cap Screws, UNC Available in Property Class 12.9 Steel
| Size | b (mm) | Pitch P (mm) | c (mm) | dw (mm) | Width across corners e (mm) | Head height k (mm) | r (mm) | Width across flats s (mm) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|
| 1/4" | 19.05 | 1.27 | 0.406 | 10.557 | 12.832 | 4.366 | 0.37 | 11.113 | 3/8"~12" | ASME B18.2.1 |
| 5/16" | 22.225 | 1.411 | 0.406 | 12.065 | 14.665 | 5.556 | 0.423 | 12.7 | 1/2"~12" | ASME B18.2.1 |
| 3/8" | 25.4 | 1.587 | 0.406 | 13.573 | 16.498 | 6.35 | 0.476 | 14.287 | 1/2"~12" | ASME B18.2.1 |
| 7/16" | 28.575 | 1.814 | 0.406 | 15.081 | 18.331 | 7.541 | 0.529 | 15.875 | 3/4"~12" | ASME B18.2.1 |
| 1/2" | 31.75 | 1.954 | 0.406 | 18.098 | 21.997 | 8.731 | 0.635 | 19.05 | 3/4"~12" | ASME B18.2.1 |
| 5/8" | 38.1 | 2.309 | 0.406 | 22.622 | 27.496 | 10.716 | 0.794 | 23.812 | 3/4"~14" | ASME B18.2.1 |
| 3/4" | 44.45 | 2.54 | 0.406 | 27.146 | 32.996 | 12.7 | 0.953 | 28.575 | 1"~14" | ASME B18.2.1 |
| 7/8" | 50.8 | 2.822 | 0.406 | 31.671 | 38.495 | 14.684 | 1.111 | 33.337 | 1 1/2"~14" | ASME B18.2.1 |
| 1" | 57.15 | 3.175 | 0.406 | 36.195 | 43.994 | 17.066 | 1.27 | 38.1 | 1 1/2"~14" | ASME B18.2.1 |
| 1 1/8" | 63.5 | 3.629 | 0.406 | 40.719 | 49.493 | 19.05 | 1.429 | 42.862 | 1 5/8"~14" | ASME B18.2.1 |
| 1 1/4" | 69.85 | 3.629 | 0.406 | 45.244 | 54.993 | 21.431 | 1.587 | 47.625 | 1 5/8"~14" | ASME B18.2.1 |
| 1 3/8" | 76.2 | 4.233 | 0.406 | 49.768 | 60.492 | 23.019 | 1.746 | 52.388 | 1 3/4"~14" | ASME B18.2.1 |
| 1 1/2" | 82.55 | 4.233 | 0.406 | 54.292 | 65.991 | 25.4 | 1.905 | 57.15 | 1 3/4"~14" | ASME B18.2.1 |
| 1 3/4" | 95.25 | 5.08 | 0.406 | 63.341 | 76.99 | 29.369 | 2.223 | 66.675 | 2"~14" | ASME B18.2.1 |
| 2" | 107.95 | 5.644 | 0.406 | 72.39 | 87.988 | 34.131 | 2.54 | 76.2 | 2 1/2"~14" | ASME B18.2.1 |
| 2 1/4" | 120.65 | 5.644 | 0.406 | 81.439 | 98.987 | 38.1 | 2.857 | 85.725 | 2 1/2"~14" | ASME B18.2.1 |
| 2 1/2" | 133.35 | 6.35 | 0.406 | 90.487 | 109.985 | 42.069 | 3.175 | 95.25 | 3"~14" | ASME B18.2.1 |
| 2 3/4" | 146.05 | 6.35 | 0.406 | 99.536 | 120.984 | 46.038 | 3.493 | 104.775 | 3"~14" | ASME B18.2.1 |
| 3" | 158.75 | 6.35 | 0.406 | 108.585 | 131.982 | 50.8 | 3.81 | 114.3 | 3 1/2"~14" | ASME B18.2.1 |
| 3 1/4" | 171.45 | 6.35 | 0.406 | 117.634 | 142.981 | 55.562 | 4.128 | 123.825 | 3 3/4"~14" | ASME B18.2.1 |
| 3 1/2" | 184.15 | 6.35 | 0.406 | 126.683 | 153.979 | 58.737 | 4.445 | 133.35 | 3 3/4"~14" | ASME B18.2.1 |
| 3 3/4" | 196.85 | 6.35 | 0.406 | 135.731 | 164.978 | 63.5 | 4.763 | 142.875 | 4"~14" | ASME B18.2.1 |
| 4" | 209.55 | 6.35 | 0.406 | 144.78 | 175.976 | 68.263 | 5.08 | 152.4 | 4"~14" | ASME B18.2.1 |
Dimensions are independent of the material: every size above is available in Property Class 12.9 Steel.
Custom manufacturing · Made to drawing
Need this bolt in a grade that is not listed?
Grade 12 9 Steel is one of the grades the catalog describes. Where the standard stops, the drawing takes over: fine pitches, left-hand threads, partial threading, and property classes above the catalogued grade where material and heat treatment allow. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
