براغي رأس أسطوانية M42-4.5 X 240mm | محرك سداسي | خيط جزئي | فولاذ سبائكي فئة 12.9 بأكسيد أسود حراري

Installed these in a jig for a production run and the 12.9 alloy steel handled the torque without any visible wear. The black oxide finish seems durable and hasn't chipped at all.

These bolts handled the heavy clamping force on my jig without any issue, the hex socket drive made tightening them in a tight spot far easier than a standard hex head would have. For the size, the 240mm length was precisely as ordered and the threads were clean right out of the box.

The thermal black oxide finish on these bolts handled the cutting fluid on my mill without any surface rust, which was my main concern. They threaded smoothly into my fixture plate and the hex socket drive gave me plenty of torque.