Property Class 8.8 Steel (ISO 898-1 property class 8.8) is the workhorse medium-carbon alloy class for structural joints. Specified on captive panel screws, spring-loaded it determines the corrosion behaviour (requires plating (zinc) for corrosion 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 8.8 Steel for Captive Panel Screws, Spring-Loaded
The workhorse medium-carbon alloy class for structural joints. For captive panel screws, spring-loaded, 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 captive panel screws, spring-loaded 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 captive panel screws, spring-loaded 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 Captive Panel Screws, Spring-Loaded Available in Property Class 8.8 Steel
| Thread size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Panel hole (mm) | Panel thickness (mm) | Retracted travel (mm) | Drive |
|---|---|---|---|---|---|---|---|
| M3 | 0.5 | 8.0 | 3.0 | 4.2 | 0.8~1.5 | 4.0 | Slotted / PH1 |
| M3 | 0.5 | 8.0 | 3.0 | 4.2 | 1.5~2.5 | 6.0 | Slotted / PH1 |
| M4 | 0.7 | 10.0 | 3.5 | 5.3 | 0.8~1.5 | 5.0 | Slotted / PH2 |
| M4 | 0.7 | 10.0 | 3.5 | 5.3 | 1.5~3.0 | 8.0 | Slotted / PH2 |
| M5 | 0.8 | 12.0 | 4.0 | 6.4 | 1.5~3.0 | 8.0 | PH2 / TX20 |
| M6 | 1.0 | 14.0 | 4.5 | 7.4 | 2.0~4.0 | 10.0 | PH3 / TX25 |
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. Where the standard stops, the drawing takes over: fine pitches, left-hand threads, partial threading, and property classes above the catalogued grade where material and heat treatment allow. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
