Key specifications
| Sizes | ST4.2, ST4.8 (#10), ST5.5 (#12), ST6.3 (#14) |
|---|---|
| Lengths | About 16 mm to 150 mm |
| Washers | Bonded EPDM with steel or aluminium backing; 14, 16 or 19 mm are common |
| Materials | Case-hardened carbon steel; stainless 410 or 304 on request |
| Finishes | Zinc plated, zinc-nickel, Ruspert-type ceramic coatings; painted heads in RAL colours |
| Drive | Hex washer head: 7, 8 or 10 mm socket depending on size |
Made to order in China and shipped FOB or CIF from Tianjin, Ningbo, Shanghai or Shenzhen. Sizes, grades and finishes outside this list can be quoted.
Dimension drawing
ISO 15480 dimensions and drilling range
The drilling range is the total steel thickness the drill point can penetrate, including any gap between sheets. Choose a size whose range covers your thickest steel stack.
| Size | Pitch (mm) | Washer face dc max (mm) | Head height k max (mm) | Across flats s (mm) | Drilling range (mm) | Inquiry |
|---|---|---|---|---|---|---|
| ST3.5 | 1.3 | 8.3 | 3.4 | 5.5 | 0.7–2.25 | Quote this size |
| ST4.2 | 1.4 | 8.8 | 4.1 | 7 | 1.75–3 | Quote this size |
| ST4.8 | 1.6 | 10.5 | 4.3 | 8 | 1.75–4.4 | Quote this size |
| ST5.5 | 1.8 | 11 | 5.4 | 8 | 1.75–5.25 | Quote this size |
| ST6.3 | 1.8 | 13.5 | 5.9 | 10 | 2–6 | Quote this size |
Choosing the screw for the job
- Thin purlins and light-gauge framing: ST4.8 or ST5.5 with a standard drill point.
- Heavier structural steel above about 5–6 mm needs a longer, heavy-duty drill point beyond the ISO table; tell us the steel thickness.
- The unthreaded drill section must be longer than the steel stack so drilling finishes before the thread engages.
- Cladding over insulation: length = sheet profile height + insulation + steel thickness + at least three thread pitches through the steel.
- In coastal and humid climates, ask for a ceramic-type coating with a stated salt-spray requirement, or stainless.
EPDM washers and colour-matched heads
The EPDM sealing washer is vulcanised to a steel or aluminium backing washer. Common outer diameters are 14, 16 and 19 mm. Heads can be painted to match the cladding colour; send the RAL or colour code and the quantity per colour, since each colour is a separate production lot.
Packing, shipping and documents
| MOQ | 500 pcs per specification; mixed sizes can be combined on one order |
|---|---|
| Lead time | 10–15 days for stock items, 25–30 days for production orders, confirmed in the quotation |
| Export packing | Inner boxes or bags labelled by size, export cartons, then palletized and stretch-wrapped; buyer labels and barcodes on request |
| Shipping ports | Tianjin, Ningbo, Shanghai, Shenzhen |
| Incoterms | EXW, FOB, CFR, CIF, DAP, DDP on request |
| HS code reference | HS 7318.14 (self-tapping screws) is the usual heading for self-drilling screws. Confirm the final code with your customs broker. |
| Certificate of origin | ACFTA Form E available on request for buyers in ASEAN countries such as Malaysia, Indonesia, Vietnam and the Philippines |
| Order documents | Commercial invoice, packing list and inspection records agreed in the quotation |
What to include in your RFQ
- Size and length, e.g. ST5.5 × 32
- Steel thickness to drill (total stack)
- Washer type and diameter, head colour
- Coating and salt-spray requirement
- Packing (bags, boxes, buckets), quantity per size, destination
Frequently asked questions
What size self-drilling screw for 3 mm steel?
ST4.8 or larger. ISO 15480 gives a drilling range of 1.75–4.4 mm for ST4.8 and 1.75–5.25 mm for ST5.5, counting the total steel thickness including gaps.
Is DIN 7504 K the same as ISO 15480?
ISO 15480 replaced DIN 7504 form K for hex washer head self-drilling screws. Many buyers still order by the DIN name.
What does #12 or #14 mean?
It is the inch gauge size: #10 is about 4.8 mm, #12 about 5.5 mm and #14 about 6.3 mm (ST4.8, ST5.5 and ST6.3).
Can you paint the heads to match roof sheets?
Yes. Send the colour code and quantity per colour; each colour is produced as its own lot.
What is the MOQ for self-drilling screws?
Reference MOQ is 500 pcs per specification. Standard sizes typically ship in 10–15 days and made-to-order sizes in 25–30 days, confirmed with each quotation. We reply to every RFQ within 2 working hours.
Sources for technical review