Definition
A descriptive phrase used in fastener and hardware references to identify screws designed to cut their own threads as they are driven into a softer base material such as aluminum, magnesium, wood, fiberglass, or plastic. Unlike machine screws, these fasteners do not require a pre-tapped hole; the screw itself forms the mating threads as it is turned in.
Plain English
Screws that make their own threads when you drive them into a soft material. You don't need to cut threads in the hole first—the screw does it as it goes in.
Context Anchor
Seen in aircraft maintenance descriptions of screws, panels, interior parts, and light-duty fasteners.
Why Pilots Care
Correct fastener selection prevents damage to aircraft components during maintenance or interior work.
Intuition Check
Do not read “soft” as meaning unsafe or flimsy. Here it means soft enough, compared with the screw, for the threads to bite into and hold.
Example Sentence 1
The interior trim panels are held in place with sheet-metal screws that are screwed into soft metal, wood, or plastic without needing pre-tapped holes.
Example Sentence 2
Interior brackets were attached using fasteners screwed into soft metal, wood, or plastic to avoid adding extra weight.