🔧 Product Overview: M3 x 18/25/30mm Knurled Thumb Screws – 303 Stainless Steel Hand Grip Bolts
For tool‑less fastening that combines a secure grip with excellent corrosion resistance, these 303 stainless steel knurled thumb screws are an ideal choice. The flat, knurled head provides a non‑slip surface for hand tightening and loosening – no screwdriver or wrench needed. Made from 303 stainless steel, they offer good machinability and corrosion resistance, making them suitable for both indoor and outdoor applications. Available in M3 thread size with three length options: 18mm, 25mm, and 30mm (measured under the head). Fully threaded with standard coarse pitch (0.5mm). Perfect for machinery access panels, 3D printers, camera rigs, and DIY projects.
✨ Why These Stainless Steel Knurled Thumb Screws Are a Workshop Essential
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303 stainless steel construction – Good corrosion resistance, excellent machinability, and moderate strength. Ideal for applications where rust is a concern.
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Flat knurled head for tool‑less grip – Diamond knurl pattern provides a secure, non‑slip surface for hand tightening and loosening – no tools required.
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M3 metric thread – fully threaded – Standard coarse pitch (0.5mm) runs the entire length for maximum grip and easy nut engagement.
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Three length options: 18mm, 25mm, 30mm – Choose the right thread length for your panel thickness or assembly depth. Length measured under the head.
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Grade 5 strength – Reliable for general fastening in electronics, machinery, and DIY applications.
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Made to GB standard – Consistent quality and precise dimensions.
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Wide applications – Machinery, 3D printer bed leveling knobs, camera rigs, electronic enclosures, and general assembly.
📏 Technical Specifications – M3 Knurled Thumb Screws (18/25/30mm)
| Product Type |
Knurled Thumb Screws (Hand Grip Bolts) |
| Material |
303 Stainless Steel |
| Thread Size |
M3 |
| Thread Pitch |
0.5mm (metric coarse) |
| Thread Length Options (under head) |
18mm, 25mm, 30mm (select from options) |
| Length Measurement |
Under head – from underside of head to tip (head not included) |
| Head Style |
Flat knurled head (diamond knurl pattern) |
| Drive Style |
Hand grip (toolless) |
| Grade |
Grade 5 |
| Standard |
GB |
❓ FAQs – 303 Stainless Knurled Thumb Screws
🔸 What is the difference between 303 and 304 stainless steel?
303 stainless contains added sulfur for improved machinability, making it easier to produce precision parts. It has slightly lower corrosion resistance than 304 but is still excellent for most indoor and light outdoor applications. For saltwater or heavy chemical exposure, 316 stainless is recommended.
🔸 Which length should I choose – 18mm, 25mm, or 30mm?
Thread length is measured from under the head to the tip. For panel thickness up to 15mm, choose 18mm. For thicker panels (15‑22mm), choose 25mm. For panels up to 27mm or when using a nut with extra engagement, choose 30mm. Measure your total material thickness and add 2‑3mm for proper thread engagement.
🔸 Are these screws fully threaded? What is the thread pitch?
Yes – fully threaded from under the head to the tip. The pitch is standard M3 coarse: 0.5mm.
🔸 Can I use these screws with nuts, or are they for tapped holes only?
These are standard machine screws – they work with matching M3 nuts or in pre‑tapped holes. For through‑hole applications, use a nut on the back side. The knurled head is for hand grip only – do not use tools on the knurling.
🔸 Will 303 stainless steel rust?
303 stainless offers good corrosion resistance for most indoor and outdoor environments. It will not rust under normal conditions. For continuous saltwater exposure, 316 stainless is a better choice. For general use, 303 is perfectly adequate.
🔸 How many screws come in a pack?
Quantity varies – please select the desired quantity from the dropdown options. You can order individual screws or in bulk.
