Using countersinks correctly: How to achieve perfect countersinking

What does a countersink actually do?

A countersink is used to deburr holes or to widen screw heads. The result: screws sit flush with the surface—especially important for metal, wood, or plastic.

The standard countersink angle is 90° , suitable for countersunk head screws. However, versions with 60°, 82°, or 120° are also available, depending on the standard and application.

Which material is the right one?

  • HSS (High Speed Steel) – robust and universal for metal, wood, plastic

  • HSS-G – ground for more precise cuts and quieter work

  • TiN-coated – with titanium nitride layer for longer service life and less friction

TiN countersinks are particularly useful when regularly machining steel or stainless steel. The gold coating protects the cutting edges and reduces friction.

Tips for a clean result

  1. Adjust the speed: It's better to go a little slower than too fast. Too high a speed generates heat and lubricates the cutting edge.

  2. Use cooling: Cutting oil or emulsion is particularly worthwhile for steel or stainless steel.

  3. Apply light pressure: The countersink should cut, not grind.

  4. Fix the workpiece: Vibrations lead to uneven countersinking.

Typical mistakes when lowering

  • Countersink too blunt → creates chatter marks

  • Wrong angle → screw heads protrude

  • No deburring of the hole before countersinking → unclean edges

With a sharp, matching countersink you can achieve precise and burr-free results .
If you countersink regularly, it's worth getting a high-quality countersink set - like the a+s HSS-G TiN countersinks , precision ground according to DIN 335 C.

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