Material specification page for square nuts, 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 B18.2.2.
Why Choose Property Class 12.9 Steel for Square Nuts, UNC
The highest common strength class, for high-load machine assembly. For square nuts, 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 square nuts, 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 Square Nuts, 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 Square Nuts, UNC Available in Property Class 12.9 Steel
| Size | Threads per inch | Width across flats s (in) | Nut height m (in) | Reference standard |
|---|---|---|---|---|
| 1/4" | 20 | 0.438 | 0.219 | ASME B18.2.2 |
| 5/16" | 18 | 0.562 | 0.266 | ASME B18.2.2 |
| 3/8" | 16 | 0.625 | 0.328 | ASME B18.2.2 |
| 7/16" | 14 | 0.75 | 0.375 | ASME B18.2.2 |
| 1/2" | 13 | 0.812 | 0.438 | ASME B18.2.2 |
| 5/8" | 11 | 1 | 0.547 | ASME B18.2.2 |
| 3/4" | 10 | 1.125 | 0.656 | ASME B18.2.2 |
| 7/8" | 9 | 1.312 | 0.766 | ASME B18.2.2 |
| 1" | 8 | 1.5 | 0.875 | ASME B18.2.2 |
| 1 1/8" | 7 | 1.688 | 1 | ASME B18.2.2 |
| 1 1/4" | 7 | 1.875 | 1.094 | ASME B18.2.2 |
| 1 3/8" | 6 | 2.062 | 1.203 | ASME B18.2.2 |
| 1 1/2" | 6 | 2.25 | 1.312 | ASME B18.2.2 |
Dimensions are independent of the material: every size above is available in Property Class 12.9 Steel.
Custom manufacturing · Made to drawing
Need this nut in a grade that is not listed?
Grade 12 9 Steel is one of the grades the catalog describes. Height and across-flats are the two most often changed — a thinner nut for clearance, a larger hex for a tool that is already on the line. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
