Countersunk (flat head) screw
ISO 10642 (hex), DIN 965 (Phillips), DIN 963 (slotted)
Sizes
M2-M20
Drive & head
Internal hex, Torx, Phillips or slotted
Materials
Alloy steel, A2/A4 stainless
Strength / grades
10.9, 12.9 steel; A2-70 stainless
Hole and pilot guidance
Metric countersinks are 90 degrees; the recess diameter must match the head so it lands flush.
Where it is used
Watch out for
- US 82-degree and metric 90-degree countersinks do not seat properly in each other.
- Over-tightening a countersunk screw can crack brittle plastic or thin castings.
- You cannot countersink into sheet that is thinner than the head depth.