Self-Drilling Screw Sizes: Complete IFI & DIN Cross-Reference Guide
Cross-reference guide for self-drilling screw sizes between IFI (#4-#14) and DIN (ST2.9-ST6.3) standards. Includes drill diameters, wire diameters, and matching drill point die specifications.
Understanding Self-Drilling Screw Size Standards
Self-drilling screws are sized using two major international standards:
- IFI (Industrial Fasteners Institute) — The American standard, using number designations (#4, #6, #7, #8, #10, #12, #14)
- DIN (Deutsches Institut für Normung) — The European standard, using ST (self-tapping) metric designations (ST2.9, ST3.5, ST3.9, ST4.2, ST4.8, ST5.5, ST6.3)
Both standards cover similar screw size ranges and can be approximately cross-referenced. However, they are not simply different names for identical specifications — they differ in tolerances, test methods, and material requirements. If you're exporting screws internationally, you need to understand both systems.
Complete IFI to DIN Cross-Reference
| IFI Size | DIN Size | Major Diameter (mm) | Drill Diameter Dø (mm) |
|---|---|---|---|
| #4 | ST 2.9 | 2.845 | 2.2–2.4 |
| #6 | ST 3.5 | 3.505 | 2.8–3.0 |
| #7 | ST 3.9 | 3.810 | 3.0–3.2 |
| #8 | ST 4.2 | 4.166 | 3.3–3.5 |
| #10 | ST 4.8 | 4.826 | 3.8–4.1 |
| #12 | ST 5.5 | 5.486 | 4.3–4.7 |
| #14 | ST 6.3 | 6.350 | 5.1–5.7 |
Note: Major diameter values are per IFI/DIN standards. Drill diameter (Dø) varies by series and manufacturer — the ranges shown above cover common production specifications and serve as a selection reference.
Drill Point Die Sizes by Screw Size
Each screw size requires a specific drill point die. The die must match the screw's wire diameter, point diameter, and target drill diameter precisely. Here's how they typically map:
IFI #4 / DIN ST 2.9 (Smallest)
- Wire diameter: ~2.0 mm
- Point diameter: ~2.2 mm
- Die styles available: MA (Style I)
- Typical application: Light-gauge sheet metal, HVAC ductwork
- Available in L1–L2 series (short drill point for thin material)
IFI #6 / DIN ST 3.5
- Wire diameter: ~2.5 mm
- Point diameter: ~2.8 mm
- Die styles available: MA, MB
- Typical application: Steel studs, light framing
- Available in L1–L2 series
IFI #7 / DIN ST 3.9
- Wire diameter: ~2.8 mm
- Point diameter: ~3.0 mm
- Die styles available: MA, MB
- Typical application: Cladding, decking fasteners
- Available in L1–L3 series
IFI #8 / DIN ST 4.2
- Wire diameter: ~3.1 mm
- Point diameter: ~3.3 mm
- Die styles available: MA, MB
- Typical application: General construction, roofing
- One of the most popular sizes in many markets
- Available in L1–L3 series
IFI #10 / DIN ST 4.8
- Wire diameter: ~3.6 mm
- Point diameter: ~3.8 mm
- Die styles available: MB
- Typical application: Roofing, siding, structural connections
- Available in L1–L4 series
IFI #12 / DIN ST 5.5
- Wire diameter: ~4.1 mm
- Point diameter: ~4.3 mm
- Die styles available: MB, MC
- Typical application: Heavy-gauge steel, structural framing
- Available in L3–L6 series; MC style in L4–L6
IFI #14 / DIN ST 6.3 (Largest)
- Wire diameter: ~4.7 mm
- Point diameter: ~5.1 mm
- Die styles available: MB, MC
- Typical application: Thick structural steel, heavy industrial
- All L-series available; MC style in L4–L6
Wire and point diameters listed above are approximate common values. Always confirm exact specifications with your die supplier for your specific screw design.
Choosing the Right L-Series for Your Substrate
The L-series (L1 through L6) determines the flute length of the drill point. Longer flutes penetrate thicker material:
| Substrate Thickness | Recommended L-Series | Typical Application |
|---|---|---|
| 0.5–1.0 mm | L1 (2.7ℓ) | Thin sheet metal, HVAC |
| 1.0–2.0 mm | L2 (4.0ℓ) | Light-gauge steel framing |
| 2.0–4.0 mm | L3 (5.7ℓ–7.5ℓ) | Medium-gauge construction |
| 4.0–8.0 mm | L4 (9.2ℓ–11.7ℓ) | Heavy-gauge steel |
| 8.0–12.0 mm | L5 (13.0ℓ–14.5ℓ) | Structural steel |
| 12.0–16.0 mm | L6 (16.5ℓ–17.7ℓ) | Thick structural applications |
Important: Match the L-series to the thickest material the screw must penetrate. Under-specifying leads to incomplete drilling; over-specifying wastes material and reduces assembly speed.
Regional Market Preferences
Different markets tend to favor different size ranges:
- North America — IFI #8 and #10 are among the most common in construction. IFI standard is primary.
- Europe — DIN ST4.2 and ST4.8 are widely used. DIN/ISO standards are primary.
- Southeast Asia — Mix of IFI and DIN depending on export destination. #8 and #10 are commonly popular.
- Middle East — Generally follows European DIN standards.
- Latin America — Mix of both standards; IFI is more common in countries with strong US trade ties.
Quality Specifications to Verify
When sourcing drill point dies for any screw size, these are commonly verified specifications:
- Drill diameter tolerance — A common target is ±0.02 mm of specification
- Flute surface finish — Mirror polish reduces friction and improves screw point quality
- Die concentricity — The two die halves must align precisely; misalignment creates off-center drill points
- Material certification — For carbide: cobalt content and grain size. For HSS: grade verification (M2, M9, or M51)
Find the Right Die for Your Screw Size
ZLD Precision Mold manufactures drill point dies for the full range of self-drilling screw sizes — IFI #4 through #14, DIN ST2.9 through ST6.3 — in all six L-series. Use our interactive specification chart to find the exact die code for your screw, or contact us for custom specifications.