Stainless steel nuts and bolts in metric sizes for printed builds, electronics and printer repairs. Choose screws by head style and nuts by type, then add SS304 washers, galvanised square nuts or a fastener kit that matches each size.
Countersunk SS304 Phillips Head Bolts Metric M2-M8
Countersunk SS304 Hex Head Bolts Metric M2-M8
Stainless Steel (SS304) Thin Hex Nuts Metric M3-M8
Stainless Steel (SS304) Standard Hex Nuts Metric M2-M8
Stainless Steel Self-Locking Nyloc Nuts Metric M2-M6
Button Head Socket Screws – Stainless Steel (M2 – M8)
M3 Fastener Starter Kit (140 pcs)
M4 Fastener Starter Kit (160 pcs)
M5 Fastener Starter Kit (160 pcs)
Small Fastener Kit (M2 and M2.5, 160 pcs)
Nut and Washer Assortment (290 pcs)
Thread Forming Screw Starter Kit (80 pcs)
Most of the hardware on this page is SS304 stainless steel, chosen for its corrosion resistance indoors and out, so it copes with damp sheds and outdoor mounts as well as the workbench. Single items are sold individually in metric sizes, so you can buy exactly what a project needs. This page covers the hardware itself. If you are still deciding how to join your parts, start with our guide to fastening methods for printed parts.
A size such as M3 x 10 carries two numbers: M3 is the nominal thread diameter of 3 mm, and 10 is the length in millimetres. Button head screws are measured from under the head, while countersunk screws are normally measured overall, because the head sits inside the part. Nuts and washers are listed by thread size alone, so an M3 nut suits any M3 screw.
Metric threads also have a pitch, the distance between neighbouring thread peaks. Everyday metric hardware uses the standard coarse pitch unless it is marked as fine, and coarse and fine threads will not mate. Our nyloc nuts, for example, are listed with a coarse thread.
| Product | Material | Sizes | Typical use |
|---|---|---|---|
| Button Head Socket Screws | Stainless steel | M3 to M8 | Low rounded head with a hex drive, tidy where the head sits on the surface |
| Countersunk SS304 Hex Head Bolts | SS304 | M2 to M8, 4 to 50 mm | Flush finish on lids and sliding parts, driven with a hex key |
| Countersunk SS304 Phillips Head Bolts | SS304 | M2 to M8, 4 to 50 mm | Flush finish, driven with a Phillips screwdriver |
| SS304 Thread Forming Screws for Plastics | SS304 | 3 x 8, 3 x 15, 4 x 10, 4 x 15 mm | Driving straight into printed plastic, with countersunk or pan washer heads |
| Standard Hex Nuts | SS304 | M2 to M8 | Through bolts and printed nut traps |
| Thin Hex Nuts | SS304 | M3 to M8 | Shallow nut traps, or locked against a second nut |
| Self-Locking Nyloc Nuts | Stainless steel with a nylon insert | M2 to M6 | Joints that see vibration, made to ISO/DIN standards |
| Square Nuts | Galvanised steel | M3 to M6 | Slots and pockets inside printed parts |
| Metric Washers | SS304 | M2 to M8 | Spreading clamping force on softer plastic |
Modelling a nut trap or a recess for a washer? These measurements come from our kit listings. Add a little clearance to the pocket, and see Designing for 3D Printing: DFM Basics for more on printed holes.
| Size | Hex nut (across flats x thickness) | Thin hex nut | Washer (inner x outer x thickness) |
|---|---|---|---|
| M2 | 3.9 x 1.6 mm | M3 and up only | 2.2 x 4.8 x 0.35 mm |
| M3 | 5.4 x 2.3 mm | 5.4 x 1.8 mm | Check the product page |
| M4 | 6.8 x 3.1 mm | 6.9 x 2.1 mm | 4.4 x 7.9 x 0.8 mm |
| M5 | 7.9 x 4 mm | 7.9 x 2.6 mm | 5.5 x 9.8 x 1 mm |
| M6 | 9.8 x 4.8 mm | 9.9 x 3.1 mm | 6.25 x 12 x 1.5 mm |
SS304 is stainless right through, which is why the screws, hex nuts and washers here suit outdoor and damp locations as well as indoor projects. The square nuts are galvanised instead, meaning steel with a protective zinc coating. They work well hidden in slots inside printed parts, but for hardware exposed to weather, SS304 hex nuts are the better pick.
For a stocked drawer, the M3, M4 and M5 Fastener Starter Kits, the Small Fastener Kit (M2 and M2.5) and the Nut and Washer Assortment bundle the same parts we sell singly for less than buying each size on its own. Orders dispatch from Perth and Melbourne, with free shipping on orders over $299 (excluding PO Boxes).
For the hex drive screws in our kits, use a 1.3 mm key for M2 countersunk screws, 2 mm for M3, 2.5 mm for M4 and 3 mm for M5. Our hex keys are sold individually from 1.3 to 5 mm, with ball ends from 2 mm up. The Phillips head bolts need a Phillips head screwdriver, offered in PH00 to PH2.
Yes. Our brass heat set inserts use standard metric threads, so an M3 screw fits an M3 insert and an M5 screw fits an M5 insert. The M3 Fastener Starter Kit is a natural partner for the M3 Heat Set Insert Pack. Pick a screw long enough to pass through the part being fixed and engage the insert fully.
Add up the thickness of everything the screw passes through, then allow enough extra to engage the nut or insert fully. A through bolt should pass completely through its nut, and with a nyloc nut the thread needs to reach past the nylon ring. The kits include several lengths of each size, which makes it easy to test before buying in quantity.
A washer spreads clamping force over a wider area, which stops a screw head or nut pulling into softer printed plastic as you tighten it. Note that the M3 Fastener Starter Kit and the Nut and Washer Assortment do not include M3 washers, so add those individually. The M4, M5 and Small Fastener Kits all come with washers.
