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Self-Drilling (Tek) vs Self-Tapping Screws: When & How to Use Each
Understand the functional difference between self-tapping and self-drilling (Tek) screws. Learn about drill point sizes (#1 to #5), material thicknesses, and driving speeds.
The Core Distinction: Pilot Hole vs Drill Point
A common misconception is that self-tapping and self-drilling screws are the exact same fastener. While all self-drilling screws are self-tapping, not all self-tapping screws can drill their own holes.
Comparison at a Glance
| Characteristic | Self-Tapping Screws (Type A / AB / B) | Self-Drilling Screws (Tek® Style) |
|---|---|---|
| Tip Geometry | Gimlet sharp point or blunt tapping point | Fluted drill bit tip (#1 to #5 point size) |
| Pre-Drilled Pilot Hole Required? | Yes (must pre-drill matching hole) | No (drills, taps & fastens in 1 operation) |
| Typical Base Materials | Sheet metal, plastic, fiberglass, softwood | Structural steel, heavy metal sheets, purlins |
| Installation Speed | Moderate (two-step operation) | Extremely fast (single-step drilling) |
Tek Screw Drill Point Sizes (#1 to #5)
Self-drilling screws are categorized by point size based on the maximum total metal thickness they can penetrate:
- Point #1: Very light sheet metal up to 1.5 mm.
- Point #2 & #3: General fabrication and steel studs up to 3.5 mm - 5.0 mm.
- Point #4 & #5: Heavy structural I-beams and hot-rolled steel up to 12.5 mm thickness.
Critical Installation Rule: RPM and Torque Control
When installing self-drilling screws into steel, using excessive drill RPM generates intense friction heat, burning out the drill point before it bites. For thick structural steel, run impact drivers at 1500 to 2500 RPM with consistent forward pressure.