BS 4174 Self-Tapping and Metallic Drive Screws

BS 4174 covers thread-forming and thread-cutting self-tapping screws, together with metallic drive screws. It includes several head styles; the drawing shows a representative pan-head tapping screw.

Technical line drawing of a pan-head self-tapping screw with nominal diameter, length, head diameter, head height and drive detail.

Self-tapping screw dimensional reference

Feature	Drawing reference	What to verify
Nominal screw diameter	d	Thread-forming or thread-cutting series
Screw length	l	Measurement origin depends on head style
Head diameter	dk	Separate limits for each specified head form
Head height	k	Separate limits for each specified head form
Drive / recess	—	Slot or recess type and applicable gauge
Point / thread form	—	Thread-forming, thread-cutting or metallic drive type

Reference note: The public BSI description identifies the covered screw types and head forms but does not publish the complete numeric schedules. This drawing is representative and schematic; consult BS 4174 for the exact head, point, thread, gauge and tolerance values.