Technical Library
The distinction matters commercially: a self-drilling screw removes a drilling operation from the assembly line, which is usually worth more than the difference in piece price between the two.
| Type | Needs a pilot hole? | Works in | Why choose it |
|---|---|---|---|
| Self-drilling drill point, sometimes called Tek-type |
No | Sheet steel, steel framing, HVAC duct, cladding | Drills, taps and fastens in one action. Removes a drilling step and the labour with it. |
| Self-tapping thread-cutting |
Yes | Thicker sections, castings, harder material | Cuts its own mating thread, removing material as a chip. Lower driving torque than forming. |
| Thread-forming for metal or for plastic |
Yes | Ductile metals, and plastic housings | Displaces rather than cuts, so no chips and a stronger, work-hardened thread. The default for plastic housings, where a chip would be a contamination and a reliability problem. |
| Machine screw into a formed thread | Tapped hole | Anything reassembled repeatedly | Where the joint will be opened and closed many times. |
Point number indicates drilling capacity - broadly, how much total steel thickness the point can get through before the threads engage. A point that is too small stalls and burns; too large and the screw drills through the substrate before the thread bites.
| Point | Indicative steel drilling capacity | Typical application |
|---|---|---|
| #1 | to ~1.2 mm | Light gauge sheet, thin cladding |
| #2 | ~0.9-2.0 mm | General sheet metal and duct |
| #3 | ~2.0-3.0 mm | Light structural, purlins |
| #4 | ~3.0-4.5 mm | Heavier steel framing |
| #5 | ~4.5-6.0 mm | Structural steel |
Capacities are indicative and vary by manufacturer, point geometry and steel grade. Confirm against the specific product data before designing an assembly around a point size - we will supply the plant's figures with a quotation.
How to use these tables. The values here are standard reference figures published to help you specify and compare parts. They are guidance, not a substitute for your own engineering standard, and several of them (torque above all) depend on assumptions about friction, lubrication and joint material that will differ in your application. Where a number matters, confirm it against the governing specification and against the part drawing. We will supply the plant's actual test data with any quotation.