Are these self-tapping or self-drilling screws?
Self-tapping. The screw cuts its own thread as it goes in, but it will not drill its own hole. That is the difference. A self-drilling screw has a drill-point tip and bores its own hole. These have an AB point, so you drill a pilot first, then drive the screw and let it tap the thread.
Do I need to pre-drill a pilot hole?
Yes. These are self-tapping, so a pilot hole is needed. Drive one into steel or thick sheet without a pilot and you risk snapping the screw or cracking the material. Drill the pilot, then fix.
What size pilot hole should I drill?
As a rule of thumb, size the pilot to roughly the screw's core (root) diameter, which is the solid centre without the thread. Go a touch smaller in thin or soft sheet so the thread bites, and a touch larger in thick or hard steel so it drives without straining. Every job is a bit different, so test on an offcut of the same material before you commit.
What is an AB point?
It is the tip type on the screw. An AB point is a sharp, gimlet-style point that starts quickly and finds the pilot hole with less wander. It is a common point for self-tapping screws going into sheet metal and thinner sections.
Why choose a pan head over a countersunk one?
A pan head sits on top of the surface with a flat, wide underside. That wide face spreads the load and clamps thin sheet without pulling through. A countersunk head sinks flush, which is better when you need a smooth surface. For stitching metal you usually want the clamping of a pan head.
Can I use these outside or into aluminium?
Keep them to interior, dry work. The corrosion rating is 1, so they are not meant for damp or exposed conditions. And avoid aluminium. TIMCO advise against zinc plated carbon steel in aluminium because of the bi-metallic reaction it can cause.
