براغي رأس مقبس M36-4 × 300mm | محرك سداسي | خيط جزئي | فولاذ سبائكي فئة 12.9 مؤكسد حراري أسود

Was slightly worried about the 12.9 hardness being brittle, but the black oxide finish handled the shop grime fine and the hex socket drove in clean without stripping. Used them for a jig build and the 300mm length gave plenty of bite through the fixture plate.

The partially threaded shaft gave me exactly the grip I needed for a jig setup, and the hex socket drive seated cleanly without any wobble. Class 12.9 alloy steel feels reassuringly solid at this size, and the black oxide still looks factory-fresh after a week of assembly work.

The black oxide finish on these screws is holding up perfectly in my jig setup, no rust after weeks of use. They threaded smoothly into the steel plate without any binding.