Material specification page for carriage bolts, unc in Property Class 12.9 Steel. Covers the grade designation (ISO 898-1 property class 12.9), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to ASME B18.5.
Why Choose Property Class 12.9 Steel for Carriage Bolts, UNC
The highest common strength class, for high-load machine assembly. For carriage bolts, 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 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.
Comparable Grades
For Carriage Bolts, 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 Carriage Bolts, UNC Available in Property Class 12.9 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 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. A non-standard bolt is quoted from the drawing; where one already exists in the catalog, the special is usually a variation on its tooling. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
