Home » GB9074.4-1988 Phillips Pan Head SEMS Screws - Stainless Steel (A2)

GB9074.4-1988 Phillips Pan Head SEMS Screws - Stainless Steel (A2)

GB9074.4-1988 Phillips Pan Head SEMS Screws – Stainless Steel A2 (SUS304) – A2-70

FULLERKREG supplies GB9074.4-1988 Phillips pan head SEMS screws manufactured from austenitic stainless steel A2 (SUS304 / 18-8), with a bright-pickled and passivated surface finish. Each screw ships with a pre-assembled flat washer (GB9074.24) and a spring washer (GB9074.26), permanently captivated on the shank — eliminating loose washer handling on the assembly line while delivering outstanding corrosion resistance.

What are Phillips Pan Head SEMS Screws?

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 during handling or installation.

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 excellent load distribution across the clamped material. The Phillips (cross-recessed) drive enables fast, reliable torquing with standard power tools and is well-suited to both manual and automated assembly environments.

Benefits of Using Phillips Pan Head SEMS Screws

  • Eliminates loose washer handling — washers are permanently captivated; no separate picking, placing, or alignment required during assembly.
  • Faster assembly — one part replaces three; dramatically reduces cycle time in high-volume production lines.
  • Reduced risk of missing washers — captive design prevents washer omission errors that can cause field failures or warranty claims.
  • Superior corrosion resistance — A2 stainless steel (SUS304) provides excellent resistance to atmospheric corrosion, moisture, and mild chemicals without any surface coating.
  • Non-magnetic & hygienic — austenitic stainless steel is non-magnetic and easy to clean, making it suitable for food processing, medical, and cleanroom environments.
  • Space-saving installation — the shortened unthreaded shank allows clamping of thinner panels; minimum clampable thickness is approximately half that of standard combination screws.
  • Compatible with legacy JIS washer dimensions — flat washer and spring washer conform to GB9074.24 dimensions, ensuring drop-in compatibility with existing designs.
  • Suitable for automated feeding — consistent geometry and captive washers make these screws ideal for vibratory bowl feeders and robotic assembly systems.
  • Anti-loosening — the pre-assembled spring washer provides continuous axial load to resist vibration-induced loosening in service.
  • No coating delamination risk — unlike zinc-plated steel, stainless steel requires no surface coating, eliminating the risk of plating flaking or peeling in service.

Material & Finish

Component Material Steel Grade Surface Treatment Strength Grade
Screw Body Stainless Steel A2 (SUS304 / 18-8) AISI 304 Bright Pickled & Passivated A2-70
Plain Washer (Flat) Stainless Steel A2 (SUS304) AISI 304 Bright Pickled & Passivated —
Spring Washer Stainless Steel A2 (SUS304) AISI 304 Bright Pickled & Passivated —

A2-70 denotes austenitic stainless steel (A2) with a minimum tensile strength of 700 MPa. The bright-pickled and passivated finish removes surface oxides and iron contamination from the manufacturing process, restoring the natural chromium oxide passive layer for maximum corrosion resistance — with no additional coating required. Typical salt-spray resistance: ≥ 200 hours to red rust.

Key mechanical properties (A2-70):

  • Tensile strength: ≥ 700 MPa
  • 0.2% proof stress: ≥ 450 MPa
  • Elongation: ≥ 20%
  • Hardness: ≤ 220 HV

Dimensional Data – GB9074.4-1988 Phillips Pan Head SEMS Screws

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 ~40
M4 0.7 8.0 2.6 PH2 0.6 varies by length ~100
M5 0.8 9.5 3.3 PH2 0.8 varies by length ~195
M6 1.0 12.0 3.9 PH3 1.0 varies by length ~335
M8 1.25 16.0 5.0 PH4 1.2 varies by length ~790

* Unit weight is approximate for a representative length (e.g., 16 mm). Stainless steel density ~7.93 g/cm³. Actual weight varies by length. Contact FULLERKREG for exact weight data per SKU.

Dimensions of Pre-Assembled Washers

The flat washer conforms to GB9074.24 dimensions. The spring washer conforms to GB9074.26. All washer components are stainless steel A2 (SUS304), matching the screw body material for full galvanic compatibility. Both washers are permanently captivated on the screw shank prior to shipment.

Flat Washer Dimensions (GB9074.24)

Thread (d) Inner Dia. d1 (mm) Outer Dia. d2 (mm) Thickness h (mm)
M3 3.2 6.0 0.5
M4 4.3 8.0 0.8
M5 5.3 9.0 1.0
M6 6.4 11.0 1.6
M8 8.4 15.0 1.6

Note: GB9074.24 plain washer outer diameters are optimized for the SEMS captive assembly process and are slightly smaller than DIN 125A equivalents.

Spring Washer Dimensions (GB9074.26)

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

Product Images

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Applications

GB9074.4-1988 Phillips pan head SEMS screws in stainless steel A2 (SUS304) / A2-70 are the preferred choice wherever corrosion resistance, hygiene, or aesthetic appearance is critical:

  • Food processing & catering equipment — stainless steel is FDA-compatible and easy to clean; ideal for food contact surfaces, processing machinery, and commercial kitchen equipment
  • Marine & coastal environments — A2 stainless steel withstands salt spray and humid marine atmospheres without rusting or staining
  • Medical & laboratory equipment — non-magnetic, non-porous, and easy to sterilize; suitable for medical device assembly and laboratory instrument housings
  • Semiconductor & cleanroom equipment — no coating particles or outgassing; captive washer design prevents loose particle contamination
  • Outdoor & architectural applications — façade panels, signage, handrails, and outdoor enclosures where long-term appearance is required
  • Electronics & precision instruments — thin panel fastening with controlled torque and no risk of coating contamination on sensitive components
  • Chemical & pharmaceutical plant — resistance to mild acids, alkalis, and cleaning agents used in process environments
  • Automated assembly lines — captive washer design is ideal for robotic and vibratory-feed assembly, reducing part count and handling errors

Particularly suited for applications where long-term corrosion resistance without maintenance is required, and where the use of zinc-plated or coated fasteners would be inappropriate due to hygiene, aesthetic, or environmental requirements.

Why FULLERKREG?

  • 🏭 Direct manufacturer — full control over material sourcing, cold forming, and passivation treatment
  • 📐 Standard-compliant — manufactured and inspected to GB9074.4-1988 with full dimensional and material traceability
  • ✅ Material certification — mill test certificates (MTC) for SUS304 / A2 stainless steel available on request
  • 🌍 Global supply — export packaging, English documentation, and worldwide logistics support
  • 📦 Bulk & wholesale ready — available in bulk bags, boxes, or custom packaging for OEM and MRO customers
  • 🔬 Quality assured — incoming material certification, hardness testing, and salt-spray testing available on request
  • 💬 Engineering support — custom sizes, A4 (SUS316) upgrades, and special specifications available; contact our technical team

For custom specifications, non-standard sizes, A4 stainless steel options, or volume pricing, please contact the FULLERKREG team directly.

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