Knurled cup point set screw
Knurl point screws are generally used to secure one object within another. The serrated ridge on the knurl cup set screw helps reduce loosening due to vibration. The knurled point combines digging action of the cup point with counter-clockwise locking knurls that have a ratchet-locking action which helps resist loosening, even under the most severe vibrations.
Knurl point set screws should not be reused because the cutting edges of the knurls are deflected when tightened. During removal, the cutting edges are torn and no longer have full strength to resist unscrewing. ISO standard for Knurled cup point set screw is ISO 4029.