For hex flange head cap screws, unc in Property Class 12.9 Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for Property Class 12.9 Steel (ISO 898-1 property class 12.9) is summarized below together with every size supplied.
Why Choose Property Class 12.9 Steel for Hex Flange Head Cap Screws, UNC
The highest common strength class, for high-load machine assembly. For hex flange 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 |
Corrosion Behavior in Service
Carbon and alloy steel hex flange head cap screws, unc require a coating for corrosion protection. Zinc plating (with or without passivation) is the most common; hot-dip galvanizing is used for outdoor structural service; black-oxide is mainly a tarnish-prevention finish for tool-room use.
Galvanic & Galling Considerations
For hex flange 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.
Sizes of Hex Flange Head Cap Screws, UNC Available in Property Class 12.9 Steel
| Size | b0 (mm) | Pitch P (mm) | c (mm) | dc (mm) | kw (mm) | r1 (mm) | Width across flats s (mm) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|
| 1/4" | 19.05 | 1.27 | 0.953 | 14.287 | 2.857 | 0.318 | 9.525 | 3/8"~4" | ASME B18.2.1 |
| 5/16" | 22.225 | 1.411 | 1.191 | 17.462 | 3.572 | 0.397 | 12.7 | 1/2"~4" | ASME B18.2.1 |
| 3/8" | 25.4 | 1.587 | 1.429 | 20.637 | 4.286 | 0.476 | 14.287 | 1/2"~5" | ASME B18.2.1 |
| 7/16" | 28.575 | 1.814 | 1.667 | 23.812 | 5.001 | 0.556 | 15.875 | 3/4"~5" | ASME B18.2.1 |
| 1/2" | 31.75 | 1.954 | 1.905 | 27.384 | 5.715 | 0.635 | 19.05 | 3/4"~6" | ASME B18.2.1 |
| 5/8" | 38.1 | 2.309 | 2.381 | 33.734 | 7.144 | 0.794 | 23.812 | 1"~6" | ASME B18.2.1 |
| 3/4" | 44.45 | 2.54 | 2.857 | 40.481 | 8.572 | 0.953 | 28.575 | 1"~6" | 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. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
