1 Pcs M3 M4 Knurled Thumb Screws Flat Head Thumb Screw Bolts Steel Nickle Plated

M3 screws have a 3 mm thread diameter and are commonly used in smaller electronics enclosures, 3D printer frames, and lightweight panels. M4 screws have a 4 mm diameter and are better suited for heavier panels, aluminum extrusion builds, and applications where higher clamping force is needed. Check the threaded insert or nut size already in your panel before selecting.

Measure the total thickness of the material being fastened, then add 2–4 mm for thread engagement beyond the panel. For example, a 2 mm steel panel with a standard nut would typically suit a 6 mm or 8 mm shaft. Longer shafts (16–20 mm) are better for thicker stacked panels or when passing through a standoff.

The first number is the outer diameter of the knurled head (e.g., 14 mm wide), and the second is the head's height or thickness (e.g., 6 mm tall). A wider head gives more grip surface and a larger bearing area against the panel. A thinner head (e.g., 12 mm × 4 mm) sits lower-profile and is better where clearance is tight.

These thumb screws are designed for panel retention and access-cover fastening rather than load-bearing structural joints. The steel core provides adequate strength for repeated panel removal and reinstallation. For high-vibration or high-load structural applications, consider using a thread-locking compound or a separate structural fastener.

Nickel plating provides a barrier against surface oxidation in typical indoor environments. It performs well in dry or low-humidity conditions such as PC cases, electronics enclosures, and workshop equipment. Prolonged exposure to moisture, salt spray, or harsh chemicals can degrade the plating over time. For outdoor or high-humidity applications, consider stainless steel alternatives.

Yes. These screws use standard metric coarse thread (M3 × 0.5 and M4 × 0.7 pitch is typical for this size range). They are compatible with standard metric hex nuts, nylon-insert lock nuts, and threaded brass or steel inserts. Always verify the pitch of your existing hardware before ordering if you are replacing existing fasteners.

Most ATX and mid-tower cases use 4–8 thumb screws for side panels and 2–4 for drive bay covers, totalling 6–12 screws per build. A pack of 10 covers a single build with spares. If you are outfitting multiple systems or want a workshop stock, packs of 15–25 offer a lower per-unit cost.