Property Class 8.8 Steel Torx Countersunk Machine Screws 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.
Torx Countersunk Machine Screws manufactured in Property Class 8.8 Steel (ISO 898-1 property class 8.8) are dimensioned to ISO 14581. 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 Torx Countersunk Machine Screws
The workhorse medium-carbon alloy class for structural joints. For torx countersunk machine screws, 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 torx countersunk machine screws 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 Torx Countersunk Machine Screws, 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 Torx Countersunk Machine Screws Available in Property Class 8.8 Steel
| Thread size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Drive size | Max torque (Nm, typical) | Common length range (mm) | Reference standard |
|---|
| M3 | 0.5 | 5.6 | 1.65 | T10 | 2.0 | 6~30 | ISO 14581 |
| M4 | 0.7 | 7.5 | 2.20 | T20 | 4.5 | 8~40 | ISO 14581 |
| M5 | 0.8 | 9.2 | 2.50 | T25 | 9.0 | 8~50 | ISO 14581 |
| M6 | 1.0 | 11.0 | 3.00 | T30 | 15.0 | 10~60 | ISO 14581 |
| M8 | 1.25 | 14.5 | 4.00 | T40 | 36.0 | 12~80 | ISO 14581 |
| M10 | 1.5 | 18.0 | 5.00 | T50 | 70.0 | 16~100 | ISO 14581 |
Dimensions are independent of the material: every size above is available in Property Class 8.8 Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
Grade 8 8 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
Where Torx Countersunk Machine Screws are used, and what decides the specification in each case. Stocked from M3 to M10.
Industries that specify Torx Countersunk Machine Screws
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Automotive assembly
The default drive on most modern vehicle assembly.
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Automated assembly
Robot and driver lines where cam-out costs cycle time.
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Electronics & appliances
Small screws driven to a controlled torque.
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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.
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Maintenance & MRO
Stocked replacements matched to an existing property class, thread and finish.
Typical applications
- roughly twice the torque of a Phillips of the same size
- transmitting torque with no axial cam-out component
- driving without down-force, so a robot arm can hold position
- clamping two machined faces to a calculated preload
- bolting brackets, motors and gearboxes to a frame
- assemblies that are dismantled for service and re-torqued
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 machine thread into unthreaded sheet or timber; use a tapping screw, rivet nut or insert made for that parent material.
Full application guide: where Torx Countersunk Machine Screws are used, how to specify them, and the cases they are wrong for
