M4-M10 Plastic Star Thumb Screws with Carbon Steel Bolt – Hand Knob Fasteners

Match the thread size (M4, M5, M6, M8, or M10) to your existing threaded hole or insert. For length, measure the depth of the threaded hole and add any material thickness you need to clamp. As a general rule, thread engagement should be at least 1× the bolt diameter — for example, an M6 bolt typically needs at least 6mm of thread engagement. Quick inch references: 16mm ≈ 5/8", 25mm ≈ 1", 30mm ≈ 1-3/16", 50mm ≈ 2", 75mm ≈ 3".

These thumb screws are designed for hand-tightened, low-torque applications such as panel fastening, access covers, jigs, and light fixtures. The carbon steel shaft generally provides adequate clamping force for typical DIY and light industrial use. They are not intended for structural load-bearing joints or high-vibration environments where a torqued fastener is required.

The carbon steel shaft is generally not rated for prolonged outdoor or high-humidity exposure without additional protection. For occasional outdoor use, applying a light coat of anti-corrosion spray to the steel shaft is recommended. The plastic knob head is moisture-resistant. For fully corrosion-resistant applications, please contact us to confirm material options.

These thumb screws use standard metric threads (M4, M5, M6, M8, M10) following ISO/DIN standards. They are compatible with metric threaded holes, inserts, and nuts. They are not compatible with UNC or UNF imperial thread systems.

Choose based on grip clearance and the torque leverage you need. D=25mm (≈1") works well in tight spaces; D=32mm (≈1-1/4") is the most common general-purpose size; D=38mm (≈1-1/2") gives more leverage for firmer clamping; D=48mm (≈1-7/8") is suited for large enclosure panels where maximum hand grip is needed.

Yes. The carbon steel shaft uses standard metric threads, so these hand knob bolts are generally compatible with standard metric hex nuts, T-nuts, threaded inserts, and weld nuts of the corresponding size. Always verify the thread pitch of your nut matches the bolt before assembly.

Each listing offers packing quantities of 1, 2, 5, 10, or 20 pieces. Select your preferred quantity from the “Thread size & Packing Qty” option above before adding to cart.