Hexagon head fit bolt  Hexagon shoulder screw with short threaded pin DIN 610, carbon steel Gr.8.8. High-strength hexagon bolts refer to grade 8.8 or above, including grade 10.9 and grade 12.9. Grade 12.9 hexagon fit bolts generally refer to natural black hexagon head screws with oil. The performance grades of hexagon fit bolts for steel structure connection are divided into more than 10 grades, including 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium-carbon steel and are heat-treated (quenched and tempered), which are generally called high-strength bolts, and the rest are generally called ordinary bolts.

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