Property Class 8.8 Steel Bearing Lock Nuts (KM Series) are supplied to ISO 898-1 property class 8.8. Corrosion behaviour is requires plating (zinc) for corrosion protection, the material is magnetic, and the usable service range is commonly limited to approx. +300 °C; confirm against the coating and the load. In practice this grade is the workhorse medium-carbon alloy class for structural joints.
- Grade
- ISO 898-1 property class 8.8
- Corrosion resistance
- Requires plating (zinc) for corrosion protection
- Magnetic response
- Magnetic
- Service temperature
- commonly limited to approx. +300 °C; confirm against the coating and the load
Property values are typical for the grade. Certified mechanical test data is available on request for production orders.
Bearing Lock Nuts (KM Series) manufactured in Property Class 8.8 Steel (ISO 898-1 property class 8.8) are dimensioned to DIN 981. The sections below give the mechanical and physical properties of the grade, its behavior in corrosive and elevated-temperature service, and the full size table.
Why Choose Property Class 8.8 Steel for Bearing Lock Nuts (KM Series)
The workhorse medium-carbon alloy class for structural joints. For bearing lock nuts (km series), 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 bearing lock nuts (km series) 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 Bearing Lock Nuts (KM Series), class 10.9 or 12.9 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 8.8 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 8.8 Steel.
Custom manufacturing · Made to drawing
Need this nut in a grade that is not listed?
Grade 8 8 Steel is one of the grades the catalog describes. Locking method is specifiable independently of the rest: nylon insert, all-metal deformed thread, serrated flange, or none. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom nut manufacturingSend a drawing
Applications & Industries
Bearing Lock Nuts are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from KM0 to KM12 (size designation).
Industries that specify Bearing Lock Nuts
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Pumps & electric motors
Shaft-end retention during rebuild.
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Bearing assemblies
Setting and holding bearings on adapter sleeves and threaded seats.
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Gearboxes & spindles
Axial location of shaft-mounted bearings.
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Maintenance & MRO
Replacements matched to the existing bolt class, thread and finish.
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Building services
Threaded rod, channel and suspension assemblies.
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Machine building & OEM
The clamping counter-face on studs and bolts throughout an assembly.
Typical applications
- used with the matching MB tab washer — the nut alone is not locked
- setting a bearing on a tapered or threaded shaft seat
- tightened with a C-spanner or pin wrench into the slots
- joints re-torqued at a service interval
- completing a bolted joint on a stud, rod or bolt
- locking an adjustment so it cannot drift
Service conditions to specify against
- Marine and coastal
- Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- High load
- Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
- Vibration
- Specified where cyclic load would loosen a plain nut or screw — rotating plant, rail, mobile equipment and anything that is not re-torqued in service.
- Match the class
- A nut below the bolt property class strips before the bolt reaches its own limit — pair class 8 nuts with 8.8 bolts, class 10 with 10.9.
Full application guide: where Bearing Lock Nuts are used, how to specify them, and the cases they are wrong for
