Property Class 8.8 Steel Hex Flange Head Cap Screws, UNC are supplied to ASME B18.2.1. The grade provides requires plating (zinc) for corrosion protection and is magnetic; the practical service range is commonly limited to approx. +300 °C; confirm against the coating and the load. Property data, grade comparison and the full size table follow.
Why Choose Property Class 8.8 Steel for Hex Flange Head Cap Screws, UNC
The workhorse medium-carbon alloy class for structural joints. For hex flange head cap screws, unc, this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 898-1 property class 8.8 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | commonly limited to approx. +300 °C; confirm against the coating and the load |
| Corrosion characteristic | Requires plating (zinc) for corrosion 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 8.8 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 8.8 Steel.
Custom manufacturing · Made to drawing
Need this bolt in a grade that is not listed?
Grade 8 8 Steel is one of the grades the catalog describes. Material and finish are usually what drives a special — a grade the standard part is not stocked in, or a coating chosen against a salt-spray figure instead of a default. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
