Property Class 12.9 Steel Oval-Head Machine Screws 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. When oval-head machine screws are specified in this grade, the dimensions remain per ASME B18.6.3; the material determines corrosion behavior (requires plating or black-oxide protection) and the service temperature range (commonly limited to approx. +300 °C; confirm against the coating and the load). Both are covered below with the size table.
Why Choose Property Class 12.9 Steel for Oval-Head Machine Screws
The highest common strength class, for high-load machine assembly. For oval-head machine screws, 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 oval-head machine screws 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 Oval-Head Machine Screws, 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 Oval-Head Machine Screws Available in Property Class 12.9 Steel
| Size example | Length (in) | Drive | Head form | Material options | Reference standard |
|---|
| #8-32 | 2 | Phillips | oval raised countersunk | 18-8 stainless steel / steel | ASME B18.6.3 |
| inch machine-screw sizes | | Phillips | oval raised countersunk | 18-8 stainless steel / steel | ASME B18.6.3 |
Dimensions are independent of the material: every size above is available in Property Class 12.9 Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
Grade 12 9 Steel is one of the grades the catalog describes. Material and finish are usually what drives a special — a grade the standard part is not stocked in, or a coating chosen against a salt-spray figure instead of a default. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom screw manufacturingSend a drawing
Applications & Industries
Oval-Head Machine Screws are bought for a small number of well-defined jobs. These are the ones we ship them for. Stocked from #8-32 to inch machine-screw sizes (nominal diameter).
Industries that specify Oval-Head Machine Screws
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Light fabrication
ASME B18.6.3 sizes fit inch machine-screw joints.
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Visible equipment
Oval heads provide a finished raised profile on covers and trim.
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Instrument panels
Phillips drive supports routine assembly in a low-profile raised seat.
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Appliance housings
Stainless and steel options match the enclosure material.
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Energy & infrastructure
Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints.
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Maintenance & MRO
Stocked replacements matched to an existing property class, thread and finish.
Typical applications
- selecting steel or 18-8 stainless
- seating a raised oval head on a prepared countersink
- choosing the under-head length for the panel stack
- using a Phillips driver on a visible machine screw
- joints where the property class is stated on the drawing
- clamping two machined faces to a calculated preload
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.
- Torque and preload
- The joint is designed around bolt tension, so lubrication, coating and the friction coefficient all change the torque figure — state them together.
Where to use something else
- Do not use an oval head in a flat-bottom counterbore; the raised profile needs its matching seat.
- Do not use a machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.
Full application guide: where Oval-Head Machine Screws are used, how to specify them, and the cases they are wrong for
