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When a standard stainless steel screw isn't enough — when the application involves saltwater exposure, chemical contact, high humidity, or medical-grade cleanliness requirements — the material grade becomes the deciding factor. Engineers, marine fabricators, precision equipment builders, and outdoor furniture manufacturers consistently specify 316 stainless steel (V4A / A4 grade) for exactly these conditions, yet finding the right size in a countersunk hex socket profile across a wide range can be surprisingly difficult.
These Allen countersunk head machine screws are made from 316 stainless steel (Grade A4 / V4A), covering thread sizes M2 through M10 and lengths from 4mm to 100mm (total length including head). The hex socket (Allen key) drive provides high torque transfer in tight spaces, while the countersunk head sits flush with or below the surface for a clean, low-profile finish. Available in packs of 1, 5, 10, or 50 pieces.
Typical applications include marine hardware and boat fittings, chemical processing equipment, outdoor and coastal structures, medical device assembly, precision electronics enclosures, furniture with flush-surface requirements, and any environment where 304 stainless steel would be insufficient.
| Head Style | Countersunk (Flat Head) |
|---|---|
| Drive Style | Hex Socket (Allen Key / Internal Hex) |
| Material | 316 Stainless Steel (V4A / A4 Grade) |
| Thread Sizes Available | M2, M2.5, M3, M4, M5, M6, M8, M10 |
| Length Range (total, incl. head) | 4mm – 100mm |
| Thread Standard | Metric coarse (ISO standard) |
| Hex Key Sizes Required | 1.5mm (M2) / 2mm (M2.5) / 2.5mm (M3) / 3mm (M4) / 4mm (M5) / 5mm (M6) / 6mm (M8) / 8mm (M10) |
| Quantity per Pack | 1, 5, 10, or 50 PCS |
| System of Measurement | Metric |
| Corrosion Resistance | Excellent (superior to 304 / A2 in chloride environments) |
316 stainless steel (also called V4A or A4 grade) contains molybdenum, which significantly improves resistance to chloride corrosion, saltwater, and acidic environments compared to 304 (A2). It is the preferred choice for marine, coastal, chemical processing, and medical applications.
Standard hex key sizes: M2 = 1.5mm, M2.5 = 2mm, M3 = 2.5mm, M4 = 3mm, M5 = 4mm, M6 = 5mm, M8 = 6mm, M10 = 8mm. These follow ISO 4762 / DIN 912 standards.
A countersunk (flat) head screw has a tapered underside that allows the head to sit flush with or below the surface when installed in a countersunk hole. Use it when a smooth, flush surface is required — common in furniture, electronics enclosures, precision equipment, and panels.
Yes. The 316 stainless steel (V4A/A4) grade is specifically recommended for outdoor, coastal, and marine environments due to its superior resistance to saltwater and chloride corrosion compared to standard 304 stainless steel.
Standard coarse metric thread pitches: M2 (0.4mm), M2.5 (0.45mm), M3 (0.5mm), M4 (0.7mm), M5 (0.8mm), M6 (1.0mm), M8 (1.25mm), M10 (1.5mm). Compatible with standard metric nuts and tapped holes.
For countersunk screws, the listed length (L) is the total length including the head. Ensure the screw length is sufficient to engage at least 1.5x the thread diameter into the receiving material for a secure hold. For thin panels, choose shorter lengths to avoid breakthrough.
These screws are available in packs of 1, 5, 10, or 50 pieces per order, allowing you to purchase the exact quantity needed for your project.
316 stainless steel is generally considered suitable for medical device assembly and food-contact applications due to its corrosion resistance and non-reactive properties. However, always verify compliance with the specific regulatory requirements of your application.
