Property Class 8.8 Steel Carriage Bolts, UNC are supplied to ASME B18.5. 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 Carriage Bolts, UNC
The workhorse medium-carbon alloy class for structural joints. For carriage bolts, 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 carriage bolts, 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 carriage bolts, 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 Carriage Bolts, UNC Available in Property Class 8.8 Steel
| Size | Threads per inch | E (in) | A (in) | H (in) | O (in) | P (in) | Q (in) | R (in) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|
| #10 | 24 | 0.179 | 0.453 | 0.104 | 0.192 | 0.11 | 0.031 | 0.031 | 3/16"~8" | ASME B18.5 |
| 1/4" | 20 | 0.236 | 0.579 | 0.135 | 0.253 | 0.141 | 0.031 | 0.031 | 3/8"~12" | ASME B18.5 |
| 5/16" | 18 | 0.298 | 0.704 | 0.166 | 0.316 | 0.172 | 0.031 | 0.031 | 1/2"~12" | ASME B18.5 |
| 3/8" | 16 | 0.358 | 0.813 | 0.198 | 0.378 | 0.203 | 0.047 | 0.031 | 1/2"~12" | ASME B18.5 |
| 7/16" | 14 | 0.418 | 0.938 | 0.229 | 0.442 | 0.234 | 0.047 | 0.031 | 3/4"~12" | ASME B18.5 |
| 1/2" | 13 | 0.479 | 1.063 | 0.26 | 0.503 | 0.266 | 0.047 | 0.031 | 3/4"~12" | ASME B18.5 |
| 5/8" | 11 | 0.601 | 1.282 | 0.329 | 0.629 | 0.329 | 0.078 | 0.062 | 3/4"~14" | ASME B18.5 |
| 3/4" | 10 | 0.723 | 1.532 | 0.391 | 0.754 | 0.391 | 0.078 | 0.062 | 1"~14" | ASME B18.5 |
| 7/8" | 9 | 0.845 | 1.782 | 0.449 | 0.88 | 0.454 | 0.094 | 0.062 | 1 1/2"~14" | ASME B18.5 |
| 1" | 8 | 0.966 | 2.031 | 0.515 | 1.006 | 0.515 | 0.094 | 0.062 | 1 1/2"~14" | ASME B18.5 |
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. Dimensions, material, finish and form are specified from the drawing — a bolt outside the standard range is a variation on existing tooling rather than a new design. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
