The spiral drill collar are made of 4145H modified chromium-molybdenum alloy steel according to API Spec 7 and aSY/T 5144 . All threads can be phosphated,copperised or cold worked. All threads are machined with CNC Lathes-Double-Shouldered and a special thread, the max diameter of spiral drill collar is 14 inch.Out diamete: 3 7/8"~ 14"(inch)Length: 9450 + 100 (mm) 螺旋钻铤采用AISI4145H铬钼钢制造，执行API规范7及SY/T 5144标准，可对螺纹进行冷滚压、镀铜或或磷化处理，可加工双台肩螺纹及其他规格的特殊螺纹，可生产外径最大14英寸的螺旋钻铤。
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