🔘 M3 x 20mm Aluminum Alloy Knurled Thumb Screw – Hand Grip Knob Bolt, Anodised Finish
You need a reliable, lightweight thumb screw for a quick‑release panel, a jig, or a piece of test equipment – and you don’t want to search for a screwdriver every time. This M3 x 20mm knurled thumb screw gives you a comfortable, diamond‑knurled aluminium head that you can tighten and loosen by hand. Made from 6061 aluminium alloy with an anodised finish, it’s corrosion‑resistant, non‑magnetic, and much lighter than steel. The 20mm thread length (under head) is fully threaded, providing a secure hold in tapped holes or with a matching M3 nut. Ideal for machinery, precision moulds, bearing assemblies, and any DIY application where tool‑less adjustment is a bonus.
✨ Key Features – M3 x 20mm Knurled Aluminium Thumb Screw
- 🔘 Knurled round head – Diamond pattern provides excellent fingertip grip, even with oily or gloved hands.
- ⚖️ Lightweight 6061 aluminium alloy – About 1/3 the weight of steel. Non‑magnetic and thermally conductive.
- 🎨 Anodised finish – Corrosion‑resistant, durable, and available in multiple colours (actual colour may vary slightly due to photography).
- 📐
Tool‑less operation – No screwdrivers, hex keys, or wrenches needed. Perfect for frequent adjustments.
- 📏 M3 metric thread (3mm diameter, 0.5mm pitch) – One of the most common sizes for electronics, machinery, and DIY.
- 📐 20mm thread length (under head) – Fully threaded from under the head to the tip for maximum grip in blind holes or with a nut.
- 🔧 Widely used – Machinery, precision moulds, bearing assembly, 3D printers, camera rigs, and workshop fixtures.
📏 Specifications – M3 x 20mm Knurled Thumb Screw
| Thread Diameter (M) |
Thread Pitch (mm) |
Thread Length (mm) |
Head Type |
Head Diameter (approx.) |
Head Height (approx.) |
Material / Finish |
Tolerance |
| M3 |
0.5 |
20 mm (under head) |
Round knurled (hand grip) |
~7‑8 mm |
~4‑5 mm |
6061 aluminium alloy / Anodised |
±0.2 mm |
* Thread length measured from underside of head to tip. Fully threaded. Slight colour differences may occur due to photography and monitor settings.
🛠️ Typical Applications for M3 Thumb Screws
| Application |
Typical Use |
| Machinery & equipment |
Quick‑release access panels, adjustment levers, tool‑less clamps |
| Precision moulds & bearing assembly |
Fixture stops, alignment blocks, temporary fastening |
| 3D printers & CNC |
Bed leveling knobs, spool holders, enclosure thumbscrews |
| Electronics enclosures |
Battery compartments, PCB covers, test equipment panels |
❓ Frequently Asked Questions – M3 Aluminium Thumb Screw
1. How do I measure the length of this thumb screw?
Length is measured from the underside of the head (where the knurling ends) to the tip of the threaded shaft. The head itself is NOT included. This screw has a 20mm threaded shaft under the head, which is ideal for panels approximately 8‑16mm thick (plus a nut if needed).
2. Is the screw fully threaded? What about the tip?
Yes – it is fully threaded from under the head to the tip, giving you maximum grip in tapped holes or when using a nut.
3. Will anodised aluminium rust? Can I use this outdoors?
The anodised finish provides good corrosion resistance for indoor and light outdoor use. For continuous saltwater or harsh chemical environments, consider stainless steel thumb screws.
4. Do I need a nut or washer with this screw?
If your equipment has a tapped M3 hole, no nut is needed. For plain holes, use a standard M3 metric nut. A flat washer is optional for load distribution.
5. Are there other colours available? The photo shows a certain colour – will mine match exactly?
We offer anodised colours on request. Due to photography and monitor calibration, slight colour differences may occur. Please contact us for specific colour availability.
6. Is this screw strong enough for load‑bearing applications?
Aluminium has lower tensile strength than steel. This thumb screw is designed for light‑duty fastening (enclosures, jigs, adjustment knobs). For heavy loads, use a steel thumb screw.
