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SK 550-050

Bore Roughness Requirements

When installing KOENIG Expander® in hard base material no positive anchoring is possible. So, to attain suitable working pressures and anchorage, it is necessary to have a bore roughness of Rz = 10-30 µm. At a roughness greater than Rz = 30 µm leakage might occur.

Roughness profile

Required roughness profile



The ideal bore roughness for anchorage is attained by drilling with a twist drill or core drill.
Undesirable roughness profile



By reaming, a one-sided, smooth roughness profile is created. This is not desirable.


Subject to technical alterations.