Property Class 12.9 Steel Tri-Wing Pan-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 Tri-Wing Pan-Head Machine Screws are supplied to our own published dimensions — this is a trade-series article rather than one covered by a dimensional standard, so confirm the figures against the part you are replacing. The grade provides requires plating or black-oxide protection and is magnetic; the practical service range is commonly limited to approx. +300 °C; confirm against the coating and the load.
Why Choose Property Class 12.9 Steel for Tri-Wing Pan-Head Machine Screws
The highest common strength class, for high-load machine assembly. For tri-wing pan-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 tri-wing pan-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 Tri-Wing Pan-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 Tri-Wing Pan-Head Machine Screws Available in Property Class 12.9 Steel
| Thread size | Head diameter (mm) | Head height (mm) | Drive | Length range (mm) |
|---|
| M3 | 5.6 | 1.8 | W2 | 6~25 |
| M4 | 8.17 | 2.92 | W4 | 6~30 |
| M5 | 9.47 | 3.37 | W5 | 10~50 |
| M6 | 12.49 | 4.44 | W6 | 10~50 |
| M8 | 15.62 | 5.53 | W7 | 10~50 |
Dimensions are independent of the material: the table above lists the sizes supplied, and on this page every one of them is quoted in Property Class 12.9 Steel. The catalogue's default material column has been omitted here so it cannot be read as contradicting that.
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. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. 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
What Tri-Wing Pan-Head Machine Screws are specified for, industry by industry. Stocked from M3 to M8.
Industries that specify Tri-Wing Pan-Head Machine Screws
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Battery equipment
Blackened or coated options match the surrounding finish.
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Production assembly
Drive sizes W2 through W7 follow the thread size.
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Appliance service
Tri-Wing drives reduce casual removal from consumer housings.
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Electronics
A2 stainless pan heads fit compact covers and shields.
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Steel fabrication
Bolted connections in frames, enclosures, walkways and weldments, on the bench and on site.
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Energy & infrastructure
Tower, pipework, switchgear and plant fixings specified for long service life and inspectable joints.
Typical applications
- choosing M3 through M8 and the supplied length range
- selecting A2, blackened or Nylok-coated finish
- using the specified Tri-Wing driver for a pan-head screw
- matching the head diameter and height to the panel
- assemblies that are dismantled for service and re-torqued
- joints where the property class is stated on the drawing
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 a Phillips bit in the Tri-Wing recess; cam-out damages the drive before the head is seated.
- 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 Tri-Wing Pan-Head Machine Screws are used, how to specify them, and the cases they are wrong for
