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When a protruding screw head isn't an option — whether you're assembling precision electronics, mounting panels, or finishing cabinetry hardware — you need a fastener that sits perfectly flush. Slotted countersunk machine screws are the go-to choice for engineers, hobbyists, and tradespeople who demand a clean, recessed finish without sacrificing holding strength.
Each screw is manufactured from A2 stainless steel (ISO 3506 Grade A2-70), featuring a fully threaded shank, an 82°–90° countersunk flat head, and a single slotted drive. Available in diameters M2, M2.5, M3, and M4, with lengths ranging from 4mm (≈5/32") to 50mm (≈2"), and sold in convenient pack quantities of 10, 20, 50, 100, or 200 pieces to suit both one-off repairs and production runs.
These metric countersunk machine screws are widely used in electronics enclosure assembly, sheet metal fabrication, optical and scientific instrument mounting, and general-purpose mechanical fastening where a flush surface is required. The slotted drive makes them compatible with basic flat-blade screwdrivers, including precision drivers for the smaller M2 and M2.5 sizes.
| Product Type | Slotted Countersunk (Flat Head) Machine Screws |
|---|---|
| Material | A2 Stainless Steel (304 / ISO 3506) |
| Grade | A2-70 |
| Drive Type | Slotted (Flat Blade) |
| Head Style | Countersunk (CSK) Flat Head |
| Thread Standard | ISO Metric Coarse (DIN 963 / ISO 2009) |
| Available Diameters | M2, M2.5, M3, M4 |
| Thread Pitch | M2: 0.4mm | M2.5: 0.45mm | M3: 0.5mm | M4: 0.7mm |
| Available Lengths | 4mm (≈5/32") to 50mm (≈2") — see variant options |
| Length Measurement | Overall length including head (countersunk screws measured from top of head to tip) |
| Pack Quantities | 10, 20, 50, 100, 200 pieces |
| Finish | Natural stainless (no coating) |
| Tensile Strength | Typically 500–700 MPa (A2-70 grade) |
| Corrosion Resistance | Good — suitable for indoor, outdoor, and light coastal use |
| Magnetic | Generally non-magnetic (may exhibit slight magnetism after cold working) |
| Country of Origin | See variant options |
| Compliance | Contact us to confirm |
For countersunk screws, the length is measured from the top of the head to the tip of the screw. Choose a length that allows the head to sit flush with or just below the surface of the material. As a general rule, the screw should engage at least 1.5× its diameter into the receiving material — for example, an M3 screw typically needs at least 4–5mm of thread engagement for a secure hold. For thin sheet metal or panels, shorter lengths (typically 4mm–10mm) are common; for structural or deeper assemblies, lengths of 16mm–50mm are generally used.
A2 stainless steel (commonly known as 304 stainless) is an austenitic grade specified under ISO 3506. The "70" in A2-70 refers to a minimum tensile strength of 700 MPa for the fastener. It offers good resistance to oxidation and general corrosion, making it suitable for a wide range of indoor and outdoor applications. It is generally non-magnetic in its annealed state, though slight magnetism may develop after cold working during manufacturing.
A2 stainless steel provides good corrosion resistance and is generally suitable for outdoor use, including light coastal exposure. However, for highly aggressive marine environments, prolonged saltwater exposure, or chemical processing applications, A4 (316) stainless steel is typically recommended. These screws are not rated for continuous submersion in seawater or chlorinated environments.
These screws follow the ISO metric coarse thread standard (DIN 963 / ISO 2009). Thread pitches are: M2 = 0.4mm, M2.5 = 0.45mm, M3 = 0.5mm, M4 = 0.7mm. They are fully compatible with standard metric nuts, threaded inserts, and tapped holes of the corresponding size. Always verify the thread pitch of your receiving component before ordering if you are unsure.
These screws require a flat-blade (slotted) screwdriver. For M2 and M2.5 sizes, a precision or jeweler's flat-head screwdriver is recommended to avoid damaging the slot. For M3 and M4, a standard flat-head screwdriver with a blade width matched to the slot width will provide the best torque transfer. Using an oversized blade can damage the screw head or surrounding material.
To convert millimeters to inches, divide by 25.4. Common conversions for this product range: 4mm ≈ 5/32", 5mm ≈ 3/16", 6mm ≈ 1/4", 8mm ≈ 5/16", 10mm ≈ 3/8", 12mm ≈ 15/32", 16mm ≈ 5/8", 20mm ≈ 25/32", 25mm ≈ 1", 30mm ≈ 1-3/16", 40mm ≈ 1-9/16", 50mm ≈ 2". These are approximate conversions — always verify against your application's dimensional requirements.
These are machine screws designed for use with pre-tapped holes, threaded inserts (such as heat-set or press-fit inserts), or matching metric nuts. They are not self-tapping and will not cut their own thread into wood, plastic, or composite materials without a pre-formed thread. For wood or plastic applications, a self-tapping or wood screw variant is generally more appropriate. In plastic enclosures, these screws work well with brass or stainless threaded inserts.
