Property Class 12.9 Steel Screw-Mount Nuts are supplied to ISO 898-1 property class 12.9. Corrosion behaviour is requires plating or black-oxide 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 highest common strength class, for high-load machine assembly.
- Grade
- ISO 898-1 property class 12.9
- Corrosion resistance
- Requires plating or black-oxide 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.
Property Class 12.9 Steel (ISO 898-1 property class 12.9) is the highest common strength class, for high-load machine assembly. Specified on screw-mount nuts it determines the corrosion behaviour (requires plating or black-oxide protection) and the service temperature range (commonly limited to approx. +300 °C; confirm against the coating and the load); the dimensions are ours rather than a standard's, and are listed in full below.
Why Choose Property Class 12.9 Steel for Screw-Mount Nuts
The highest common strength class, for high-load machine assembly. For screw-mount nuts, 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 screw-mount nuts 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 screw-mount nuts 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 Screw-Mount Nuts Available in Property Class 12.9 Steel
| Thread size | Base diameter (in) | Base thickness (in) | Barrel diameter (in) | Barrel height (in) | Mounting-hole diameter (in) | Mounting holes |
|---|
| 6-32 | 9/16 | 1/32 | 11/64 | 1/4 | 5/64 | 3 |
| 8-32 | 23/32 | | 7/32 | | | 3 |
| 10-24 | 3/4 | | 1/4 | 9/32 | 7/64 | 3 |
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.
Custom nut manufacturingSend a drawing
Applications & Industries
Screw-Mount Nuts are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from 6-32 to 10-24 (nominal diameter).
Industries that specify Screw-Mount Nuts
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Repair work
A replacement nut can be installed without changing the panel thread.
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Appliance panels
Three-hole mounting nuts add a threaded barrel to a thin sheet.
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Electrical housings
Screws, rivets or nails hold the base when a rear nut is not practical.
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Light fabrication
Base and barrel dimensions fit small brackets and covers.
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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
- using screws, rivets or nails in the base holes
- mounting a threaded barrel through three small fixing holes
- matching base diameter and barrel height to the panel
- selecting the 6-32, 8-32 or 10-24 thread
- joints re-torqued at a service interval
- completing a bolted joint on a stud, rod or bolt
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.
- 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.
Where to use something else
- Do not assume the mounting holes carry the same load as a through-bolted flange; the thin base and parent sheet govern retention.
Full application guide: where Screw-Mount Nuts are used, how to specify them, and the cases they are wrong for
