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FULLERKREG supplies GB9074.4-1988 Phillips pan head SEMS screws manufactured from alloy steel 10B21, heat-treated to strength class 8.8, with a trivalent chromate (Zinc Cr3) surface finish. Each screw ships with a pre-assembled flat washer (GB9074.24 / DIN 125A) and a spring washer (GB9074.26), permanently captivated on the shank — eliminating loose washer handling on the assembly line.
SEMS screws (also called combination screws or pre-assembled screws) are fasteners in which one or more washers are permanently captured on the screw shank before threading. The washer(s) are assembled onto the blank shank and then the thread is rolled, making the outer diameter of the thread larger than the inner diameter of the washer — so the washer can never fall off.
GB9074.4-1988 defines the Chinese national standard for cross-recessed (Phillips) pan head combination screws with pre-assembled spring washer and plain washer. The assembly is expressed as:
GB9074.4 = GB818 (Pan Head Screw) + GB9074.24 (Plain Washer) + GB9074.26 (Spring Washer)
The pan head profile provides a broad, low-profile bearing surface for load distribution. The Phillips (cross-recessed) drive enables fast, reliable torquing with standard power tools in automated assembly environments.
| Component | Material | Surface Treatment | Strength / Grade |
|---|---|---|---|
| Screw Body | Alloy Steel 10B21 | Zinc Cr3 (Trivalent Chromate) | Class 8.8 |
| Plain Washer (Flat) | SWRH62 / Low Carbon Steel | Zinc Cr3 (Trivalent Chromate) | — |
| Spring Washer | SPCC / Carbon Steel | Zinc Cr3 (Trivalent Chromate) | — |
Zinc Cr3 (trivalent chromate / RoHS-compliant zinc plating) provides excellent corrosion resistance while meeting environmental regulations. Typical salt-spray resistance: ≥ 72 hours to white rust.
Thread range: M3 – M8 | Length range: 5 mm – 50 mm | Drive: Phillips (Cross Recessed, Type H)
| Thread (d) | Pitch (mm) | Head Dia. dk (mm) | Head Height k (mm) | Drive No. | Min. Clamp Thickness (mm) | Max. Clamp Thickness (mm) | Unit Weight (g/100 pcs)* |
|---|---|---|---|---|---|---|---|
| M3 | 0.5 | 5.6 | 2.0 | PH1 | 0.5 | varies by length | ~38 |
| M4 | 0.7 | 8.0 | 2.6 | PH2 | 0.6 | varies by length | ~95 |
| M5 | 0.8 | 9.5 | 3.3 | PH2 | 0.8 | varies by length | ~185 |
| M6 | 1.0 | 12.0 | 3.9 | PH3 | 1.0 | varies by length | ~320 |
| M8 | 1.25 | 16.0 | 5.0 | PH4 | 1.2 | varies by length | ~750 |
* Unit weight is approximate for a representative length (e.g., 16 mm). Actual weight varies by length. Contact FULLERKREG for exact weight data per SKU.
The flat washer conforms to DIN 125A dimensions. The spring washer conforms to GB9074.26 (equivalent to DIN 127B). Both washers are permanently captivated on the screw shank.
| Thread (d) | Inner Dia. d1 (mm) | Outer Dia. d2 (mm) | Thickness h (mm) |
|---|---|---|---|
| M3 | 3.2 | 7.0 | 0.5 |
| M4 | 4.3 | 9.0 | 0.8 |
| M5 | 5.3 | 10.0 | 1.0 |
| M6 | 6.4 | 12.0 | 1.6 |
| M8 | 8.4 | 16.0 | 1.6 |
| Thread (d) | Inner Dia. d1 (mm) | Outer Dia. d2 (mm) | Thickness s (mm) | Height h (mm) |
|---|---|---|---|---|
| M3 | 3.1 | 5.1 | 0.8 | 1.6 |
| M4 | 4.1 | 6.8 | 0.9 | 1.8 |
| M5 | 5.1 | 8.2 | 1.2 | 2.4 |
| M6 | 6.1 | 9.9 | 1.6 | 3.2 |
| M8 | 8.1 | 13.0 | 2.0 | 4.0 |
| [Image 1] | [Image 2] | [Image 3] | [Image 4] |
GB9074.4-1988 Phillips pan head SEMS screws are widely used wherever fast, reliable, and washer-retaining fastening is required:
Particularly suited for applications where panel thickness is limited — the shortened unthreaded shank allows clamping of panels as thin as approximately half the minimum thickness achievable with standard combination screws. Refer to the dimensional table for minimum clampable thickness per size.
For custom specifications, non-standard sizes, or volume pricing, please contact the FULLERKREG team directly.
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