Property Class 12.9 Steel Bearing Lock Nuts (KM Series) combine the dimensional form of DIN 981 with the material properties of grade ISO 898-1 property class 12.9: requires plating or black-oxide protection, magnetic, service range commonly limited to approx. +300 °C; confirm against the coating and the load. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.
Why Choose Property Class 12.9 Steel for Bearing Lock Nuts (KM Series)
The highest common strength class, for high-load machine assembly. For bearing lock nuts (km series), 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 |
Galvanic & Galling Considerations
For bearing lock nuts (km series) 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.
Comparable Grades
For Bearing Lock Nuts (KM Series), 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 Bearing Lock Nuts (KM Series) Available in Property Class 12.9 Steel
| Size | Thread size | Outer diameter D (mm) | Nut height m (mm) | Slot width (mm) | Slot depth (mm) | Matching tab washer | Reference standard |
|---|---|---|---|---|---|---|---|
| KM0 | M10x0.75 | 18 | 4 | 3 | 2 | MB0 | DIN 981 |
| KM4 | M20x1.0 | 32 | 6 | 4 | 2 | MB4 | DIN 981 |
| KM6 | M30x1.5 | 45 | 7 | 5 | 2 | MB6 | DIN 981 |
| KM8 | M40x1.5 | 58 | 9 | 5 | 2.5 | MB8 | DIN 981 |
| KM10 | M50x1.5 | 70 | 9 | 6 | 2.5 | MB10 | DIN 981 |
| KM12 | M60x2.0 | 80 | 11 | 6 | 3 | MB12 | DIN 981 |
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. Thread size is the obvious variable and rarely the interesting one — height for clearance, across-flats for the tool already in the cell, and the locking feature for the vibration actually present. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
