Grade 8.8 Steel Shoulder Bolts combine the dimensional form of ISO 7379 with the material properties of grade class 8.8: requires plating (zinc) for corrosion protection, magnetic, service range up to approx. +300 °C. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.
Why Choose Grade 8.8 Steel for Shoulder Bolts
The workhorse medium-carbon alloy grade for structural joints. For shoulder bolts, this matters when requires plating (zinc) for corrosion protection is the primary requirement.
Mechanical & Physical Properties
| Grade designation | class 8.8 |
|---|---|
| Magnetic response | Magnetic |
| Service temperature | up to approx. +300 °C |
| Corrosion characteristic | Requires plating (zinc) for corrosion protection |
Galvanic & Galling Considerations
For shoulder bolts 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 Shoulder Bolts, 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 Shoulder Bolts Available in Grade 8.8 Steel
| Shoulder diameter (mm) | Thread size | Pitch (mm) | Shoulder length range (mm) | Head diameter dk (mm) | Head height k (mm) | Reference standard |
|---|---|---|---|---|---|---|
| 4.0 | M3 | 0.5 | 8~50 | 8.0 | 4.3 | ISO 7379 / DIN 9841 |
| 5.0 | M4 | 0.7 | 8~63 | 9.5 | 5.3 | ISO 7379 / DIN 9841 |
| 6.0 | M5 | 0.8 | 10~63 | 11.0 | 6.5 | ISO 7379 / DIN 9841 |
| 8.0 | M6 | 1.0 | 10~80 | 13.0 | 8.0 | ISO 7379 / DIN 9841 |
| 10.0 | M8 | 1.25 | 12~100 | 16.0 | 10.0 | ISO 7379 / DIN 9841 |
| 12.0 | M10 | 1.5 | 16~100 | 18.0 | 12.0 | ISO 7379 / DIN 9841 |
| 16.0 | M12 | 1.75 | 20~125 | 24.0 | 16.0 | ISO 7379 / DIN 9841 |
| 20.0 | M16 | 2.0 | 25~160 | 30.0 | 20.0 | ISO 7379 / DIN 9841 |
| 25.0 | M20 | 2.5 | 32~200 | 36.0 | 25.0 | ISO 7379 / DIN 9841 |
| 30.0 | M24 | 3.0 | 40~200 | 45.0 | 30.0 | ISO 7379 / DIN 9841 |