Fixture nuts according to DIN 6330 have a spherical surface to match conical seats DIN 6319 (EH 23050.).
With this combination of fixture nut and conical seat, non-parallel clamping surfaces can be compensated.
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1) DIN standards do not include these dimensions.
2) DIN standard do not include these material.
For torques and strengths please refer to appendix - Technical Data -