Self-Drilling Screw Sizes: Complete IFI & DIN Cross-Reference Guide

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, ST3.8, ST4.2, ST4.8, ST5.5, ST6.3)

Both standards describe the same physical screw sizes — they're just different naming conventions used in different markets. If you're exporting screws internationally, you need to know both.

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 3.8 | 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: Drill diameter (Dø) varies by series and manufacturer. The ranges shown above cover common production specifications.

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 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
All L-series (L1–L6) available

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
All L-series available

IFI #7 / DIN ST 3.8

Wire diameter: ~2.8 mm
Point diameter: ~3.0 mm
Die styles available: MA, MB
Typical application: Cladding, decking fasteners
All L-series available

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
Most popular size in many markets
All L-series available

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
All L-series available

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
All L-series available; 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

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: Always 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 dominate construction. IFI standard is primary.
Europe — DIN ST4.2 and ST4.8 are most common. DIN/ISO standards are primary.
Southeast Asia — Mix of IFI and DIN depending on export destination. #8 and #10 most popular.
Middle East — Generally follows European DIN standards.
Latin America — Mix of both standards; IFI more common in countries with strong US trade ties.

Quality Specifications to Verify

When sourcing drill point dies for any screw size, verify these critical specifications:

Drill diameter tolerance — Should be within ±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.