What are GB9074.17 Hex Head SEMS Screws?
GB9074.17 Hex Head SEMS Screws are pre-assembled combination fasteners consisting of three integrated components: a hexagon head bolt (per GB5783), a flat washer (per GB9074.24), and a spring lock washer (per GB9074.26). The washers are permanently captured on the screw shank during manufacturing — they cannot fall off during handling or installation, eliminating the need for manual washer placement on the assembly line.
The standard designation is: GB9074.17 = GB5783 (Hex Bolt) + GB9074.24 (Flat Washer) + GB9074.26 (Spring Washer)
This combination fastener is widely used in high-volume manufacturing and automated assembly environments where efficiency, consistency, and reliability are critical. A single fastener replaces three separate components, dramatically reducing assembly time and the risk of missing or misaligned washers.
Benefits of Using GB9074.17 Hex Head SEMS Screws
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Captive Washer Design: Flat washer and spring washer are permanently retained on the shank — no loose parts, no dropped washers during assembly.
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Faster Assembly: Eliminates the need to pick and place individual washers, significantly reducing assembly cycle time in production lines.
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Reduced Error Rate: Prevents missing washers or incorrect washer stacking — critical in automated and high-speed assembly.
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Consistent Clamping: The spring washer provides reliable anti-loosening performance; the flat washer distributes load evenly across the bearing surface.
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Simplified Inventory: One SKU replaces three separate fastener components, streamlining procurement and warehousing.
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Corrosion Resistance: A2 stainless steel with passivation finish ensures long-term performance in humid, chemical, or outdoor environments.
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Compliance Ready: Manufactured to GB9074.17-1988 national standard, ensuring dimensional and mechanical traceability.
Material & Finish
| Component |
Material |
Grade / Standard |
Surface Finish |
| Hex Bolt (GB5783) |
Stainless Steel A2 (SUS304) |
A2-70 |
Passivated / Whitened |
| Flat Washer (GB9074.24) |
Stainless Steel A2 (SUS304) |
A2 |
Passivated / Whitened |
| Spring Washer (GB9074.26) |
Stainless Steel A2 (SUS304) |
A2 |
Passivated / Whitened |
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Material: A2 Stainless Steel (equivalent to SUS304 / 1.4301)
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Strength Class: A2-70
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Surface: Passivated & Whitened (natural stainless appearance, enhanced corrosion resistance)
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RoHS Compliant: Yes
Dimensions of Pre-Assembled Washers in GB9074.17 Hex Head SEMS Screws
The flat washer dimensions in GB9074.17 SEMS screws conform to GB9074.24. The spring washer conforms to GB9074.26. All dimensions in millimeters (mm).
Flat Washer Dimensions (GB9074.24)
| Thread Size |
Inner Diameter d₁ (mm) |
Outer Diameter 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 |
| M10 |
10.5 |
20.0 |
2.0 |
| M12 |
13.0 |
24.0 |
2.5 |
| M16 |
17.0 |
30.0 |
3.0 |
| M20 |
21.0 |
37.0 |
3.0 |
Spring Washer Dimensions (GB9074.26)
| Thread Size |
Inner Diameter d₁ (mm) |
Outer Diameter d₂ (mm) |
Thickness s (mm) |
Width b (mm) |
| M3 |
3.1 |
5.1 |
0.8 |
1.0 |
| M4 |
4.1 |
6.9 |
1.0 |
1.4 |
| M5 |
5.1 |
8.7 |
1.2 |
1.7 |
| M6 |
6.1 |
10.5 |
1.6 |
2.2 |
| M8 |
8.1 |
13.5 |
2.0 |
2.7 |
| M10 |
10.2 |
16.5 |
2.5 |
3.2 |
| M12 |
12.2 |
19.5 |
3.0 |
3.7 |
| M16 |
16.2 |
25.5 |
4.0 |
4.7 |
| M20 |
20.2 |
31.5 |
5.0 |
5.7 |
Dimensional Data — GB9074.17 Hex Head SEMS Screws
All dimensions in millimeters (mm). Bolt dimensions per GB5783. Nominal lengths (l) range from 6 mm to 200 mm depending on thread size.
| Thread Size |
Pitch P (mm) |
Head Width Across Flats s (mm) |
Head Width Across Corners e (mm) |
Head Height k (mm) |
Shank Diameter d₂ (mm) |
Min. Thread Length b (mm) l≤125 |
Min. Thread Length b (mm) l>125 |
Est. Unit Weight (g/pc) — M×20mm ref. |
| M3 |
0.5 |
5.5 |
6.01 |
2.0 |
2.86 |
12 |
— |
0.5 |
| M4 |
0.7 |
7.0 |
7.66 |
2.8 |
3.82 |
14 |
— |
1.1 |
| M5 |
0.8 |
8.0 |
8.79 |
3.5 |
4.82 |
16 |
— |
2.0 |
| M6 |
1.0 |
10.0 |
11.05 |
4.0 |
5.82 |
18 |
24 |
3.5 |
| M8 |
1.25 |
13.0 |
14.38 |
5.3 |
7.78 |
22 |
28 |
8.0 |
| M10 |
1.5 |
16.0 |
17.77 |
6.4 |
9.78 |
26 |
32 |
15.0 |
| M12 |
1.75 |
18.0 |
20.03 |
7.5 |
11.73 |
30 |
36 |
25.0 |
| M16 |
2.0 |
24.0 |
26.75 |
10.0 |
15.73 |
38 |
44 |
65.0 |
| M20 |
2.5 |
30.0 |
33.53 |
12.5 |
19.67 |
46 |
52 |
130.0 |
Note: Unit weights are reference values for A2 stainless steel at the indicated nominal length. Actual weights vary by length. Contact FULLERKREG for weight data at specific lengths.
Product Showcase
Applications
GB9074.17 Hex Head SEMS Screws are engineered for demanding assembly environments where speed, reliability, and corrosion resistance are required:
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Electronics & Electrical Enclosures: Sheet metal chassis, control panels, switchgear cabinets — where captive washers prevent contamination from loose hardware.
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Automotive & EV Manufacturing: Body panels, battery enclosures, brackets — high-volume assembly lines benefit from the single-piece pick-and-place design.
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HVAC & Ventilation Equipment: Duct flanges, fan housings, air handling units — stainless steel resists moisture and condensation.
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Industrial Machinery: Guards, covers, access panels — spring washer provides vibration resistance in dynamic environments.
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Food Processing & Pharmaceutical Equipment: A2 stainless steel and passivated finish meet hygiene requirements for washdown environments.
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Marine & Outdoor Structures: Enclosures, junction boxes, structural brackets exposed to salt air or weather.
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Renewable Energy: Solar panel mounting frames, wind turbine enclosures — corrosion resistance and reliable clamping force are essential.
Why FULLERKREG?
- 🏭 Direct Manufacturer: In-house production with full dimensional and material traceability to GB9074.17-1988.
- 📦 Wholesale & Bulk Supply: Competitive pricing for OEM, MRO, and distribution customers with flexible MOQ.
- 🔬 Quality Assurance: 100% dimensional inspection; material certificates (Mill Test Reports) available on request.
- 🌍 Global Export: Experienced in international shipping, export documentation, and compliance requirements.
- ⚡ Fast Lead Times: Large stock of standard sizes; custom lengths and packaging available.
- 🤝 Technical Support: Engineering team available to assist with fastener selection, torque specifications, and application guidance.
