Choosing The Right Self-Drilling Screws – A Guide To Threaded Point Specifications

Self-drilling screws are the most common and widely used fasteners in construction and home improvement.

Their unique threaded point (also called drill tip or drill bit structure) combines drilling and threading into one step. Here’s a simple guide to understanding and selecting the best screws for your project.

 Key Functions of the Threaded Point

1. Drilling The twisted drill-shaped tip penetrates materials like metal sheets, wood, or plastic without pre-drilling. This saves time and steps during installation.

2. Threading After drilling, the wide threads behind the tip squeeze and form an internal thread in the material. This creates a strong grip without loose debris (especially for cutting-type screws).

3. Stronger Connections The design improves pull-out resistance and holding power, making screws less likely to loosen under long-term weight, such as in steel structures.

4. Works on Multiple Materials The hardened tip (HRC 58-62) can handle metals (0.75–12mm thick), wood, and plastics. Ideal for thin material joins.

Threaded Point Lengths and Selection Tips

The length of the threaded point affects how deep it penetrates. Common sizes:

· #1: 3–4mm

· #2: 4–5mm

· #3: 5–6mm

· #4: 6–8mm

· #5: 8–12mm

Selection Formula:

Threaded point length ≥ (Total material thickness) × 1.2

Multiply the material thickness by 1.2 to ensure full penetration with extra room.

How to Choose the Right Screw

1. By Material Type

· Metal Sheets (e.g., corrugated steel): Use #3 threaded point (ST4.8-5.5mm) for balanced penetration.

· Wood/Plastic: Choose composite-type threaded points with winged cutters to first widen the hole, then thread.

· Stainless Steel/Hard Materials: Opt for #5 threaded point (ST6.3mm) with tungsten carbide coating for wear resistance.

2. By Load Requirements

· Heavy Loads (e.g., steel structures): Pick hex washer head + stainless steel (304/410 grade) with pull-out resistance ≥3.2kN.

· Regular Fixing: Carbon steel threaded points (1022A grade) are cost-effective.

3. By Installation Tools

· Drill power <600W: Use #1-#2 short threaded points to avoid overheating.

· High-speed drills: Select #4-#5 long threaded points, but limit speed (stainless steel: 1500-2000 RPM).

Summary

The threaded point is the core of self-drilling screws, enabling “drill-thread-lock” in one step. Choose based on:

· Light steel structures: #3 threaded point.

· Heavy metals: #5 threaded point.

· Composite materials: Special cutter designs.

For real projects, refer to penetration tests (e.g., stainless steel with 1500-hour salt spray resistance)

If you have any questions about the selection of threaded point in screw customization, please discuss and exchange with GORUN Screw.