M42-4.5 X 220mm 소켓 캡 나사 | 육각 소켓 드라이브 | 부분 나사산 | 클래스 12.9 합금강 열처리 블랙 옥사이드

The threads cut clean and precise on these 12.9 alloy steel screws—they seated perfectly into my jig’s tapped holes without any binding. The 220mm length gave me just the reach I needed for a heavy machinery fixture.

The black oxide finish is beautifully consistent across all ten bolts and the threading is clean all the way, which made them seat perfectly in my jig fixture. For 12.9 alloy steel at this size, the weight alone tells you these aren't going to flex under load.

I needed a heavy-duty fastener for a press fixture, and the 12.9 alloy steel on these is noticeably tougher than standard screws. The thermal black oxide finish kept them from binding during assembly, which saved me a lot of frustration.