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When you need a fastener you can tighten and release by hand — without reaching for a screwdriver — standard bolts slow you down. Makers, machinists, and workshop builders who work with enclosures, jigs, access panels, and adjustable fixtures need a thumb screw they can trust to stay put and resist corrosion over time.
These knurled flat head thumb screws are machined from 303 stainless steel, a free-machining alloy known for its smooth surface finish and solid corrosion resistance. Available in M5 and M6 thread diameters with lengths ranging from 8mm to 35mm (approximately 0.31 in to 1.38 in). The M5 head measures 16mm in diameter × 6mm thick; the M6 head measures 20mm in diameter × 7mm thick. The knurled flat head profile sits flush or near-flush against the mating surface, keeping a clean, low-profile appearance.
Typical applications include securing electronics enclosure lids for quick-access maintenance, clamping workholding fixtures on CNC routers and milling tables, and fastening removable guards or covers on DIY fabrication projects where tool-free thumb screw fasteners are preferred over hex bolts.
The wide knurled flat head gives your fingers enough grip surface to tighten and loosen securely without any tools — ideal for panels and covers you access regularly.
Machined from 303 SS for reliable corrosion resistance in indoor and light-outdoor environments, with a smooth, consistent surface finish on every piece.
Choose M5 (16mm head Ø, 6mm thick) or M6 (20mm head Ø, 7mm thick) to match your existing threaded inserts or tapped holes without modification.
Select from M5×8/10/12/16mm and M6×25/30/35mm to match your stack-up thickness — no need to cut or modify the fastener.
Order exactly what your project needs — from a single piece for prototyping to 30-piece packs for production runs or workshop stock.
The flat head sits low against the surface, avoiding snag points on enclosures and panels while maintaining a clean, finished look on your build.
| Material | 303 Stainless Steel |
|---|---|
| Thread Standard | Metric (ISO) |
| Thread Sizes | M5, M6 |
| Length Range | 8mm – 35mm (0.31 in – 1.38 in) |
| M5 Head Diameter | 16mm (0.63 in) |
| M5 Head Thickness | 6mm (0.24 in) |
| M6 Head Diameter | 20mm (0.79 in) |
| M6 Head Thickness | 7mm (0.28 in) |
| Head Style | Flat Head (Knurled) |
| Drive Style | Hand / Thumb (no tool required) |
| Surface Finish | Machined, natural stainless |
| Shape | Round |
| Available Quantities | 1, 2, 3, 5, 8, 10, 15, 20, 25, 30 PCS |
| Thread Pitch | See variant options |
| Weight (per piece) | See variant options |
M5 refers to a 5mm nominal thread diameter and M6 to a 6mm diameter. Choose based on the thread size already tapped or inserted in your part. M5 screws have a 16mm head diameter; M6 screws have a 20mm head diameter, giving a larger grip surface. If you are designing from scratch, M6 is generally preferred for panels that need frequent removal due to the larger, easier-to-grip head.
Measure the total thickness of the material being clamped (the grip length), then add the thread engagement depth you need — typically 1× to 1.5× the thread diameter for stainless steel into steel. For example, clamping a 5mm panel into a 6mm deep tapped hole in aluminum with M5 thread, a 12mm screw (5mm grip + ~7mm engagement) is a reasonable starting point. Always verify fit before final assembly.
303 stainless steel thumb screws are suitable for light-to-moderate clamping loads such as securing access panels, enclosure lids, and adjustable fixtures. They are not intended for high-tensile structural joints or applications subject to heavy vibration without a locking element. For vibration-prone environments, consider adding a nylon-insert nut or thread-locking compound on the mating side.
303 stainless steel offers good corrosion resistance in dry indoor and light-outdoor environments. It is not recommended for continuous exposure to saltwater, chlorinated water, or highly acidic environments — for those conditions, 316 stainless steel is a better choice. For typical workshop, electronics enclosure, and light-industrial use, 303 SS performs reliably without surface treatment.
The flat head profile is designed to sit flush against a flat or countersunk surface. If your panel has a countersunk hole, the head will recess flush. On a flat surface without countersinking, the head will sit proud (above the surface). Ensure your mating surface geometry matches your intended installation before ordering.
Yes. These thumb screws work with any material that has a compatible M5 or M6 threaded hole — including aluminum (tapped or with threaded inserts), engineering plastics with brass or stainless inserts, and hardwood with threaded inserts. Avoid threading directly into soft plastics or wood without an insert, as repeated hand-tightening can strip the threads over time.
Multi-piece packs reduce per-unit cost and ensure you have spares on hand for future builds or replacements. For workshop stock, 10–30 piece packs of the most common sizes (M5×12mm, M6×25mm) are a practical choice. Single-piece options are available if you only need one for a prototype or repair.
