Quick answer
Countersink angle must match the screw head angle: 82° for UNC (inch/unified) screws, 90° for ISO metric screws (most common), and 100° for aerospace (AN/MS) fasteners. Using the wrong angle leaves a gap or a proud screw head. Lihao Technology offers HSS-E cobalt countersinks from 60° to 120°.
Angle standard table
| Angle | Standard | Typical application |
|---|---|---|
| 60° | Special / custom | Specific countersunk designs, custom jobs |
| 82° | UNC / Unified inch | Inch flat-head screws (USA, inch-based industries) |
| 90° | ISO / GB metric | Metric flat-head screws — most common worldwide |
| 100° | Aerospace AN/MS | Aircraft and aerospace fasteners |
| 110° | European / some screw lines | German and European equipment |
| 120° | Special / screw industry | Special countersunk heads |
82° countersink — UNC inch screws
Inch-series flat-head screws (UNC/UNF, e.g. #6, #8, 1/4 inch) use an 82° head angle. If your drawings are in inches or you export to the USA, choose 82° countersinks.
90° countersink — ISO metric screws
Metric flat-head screws (DIN 963/965, GB/T) use a 90° head angle. 90° is the most common countersink angle in the world — most sheet metal, enclosure and automotive jobs use it.
100° countersink — aerospace
Aerospace flat-head rivets and screws (AN/MS series) use a 100° countersink for flush joints on aircraft skins. Angle tolerance is critical here: Lihao Technology grinds ±0.1° for repeatable aerospace-grade seats.
What happens if I use the wrong angle?
The screw head will not seat flush — it either stands proud (risking snagging and poor clamping) or sinks too deep and weakens the material. Always match the countersink angle to the fastener head angle.
Available from Lihao Technology
We manufacture HSS-E cobalt countersinks in 60°, 82°, 90°, 100°, 110° and 120°, single-flute and 3-flute (DIN 335), factory direct with ±0.1° angle tolerance and custom angles on request.
Frequently asked questions
What is the most common countersink angle?
90° — it matches ISO metric flat-head screws, the most widely used standard worldwide.
82° or 90° countersink — which do I need?
Check the screw: inch (UNC) screws use 82°, metric screws use 90°. When in doubt, measure the screw head angle or check the standard on the drawing.
Do aerospace countersinks need a special angle?
Yes — 100° for AN/MS fasteners, with tight tolerance. High-quality HSS-E countersinks with ±0.1° tolerance keep flush joints consistent.
Can Lihao Technology make custom angles?
Yes, we support custom countersink angles and dimensions for volume orders.
