The spiral drill collars are made of 4145HMOD modified chromium-molybdenum alloy steel according to API Spec 7-1 . 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) Depth of cut: 4.0 ~ 11.9 (mm) Length: 9150+150(mm) Standard size�?� for�?� drill collar Connection # OD ID L mm DF mm Bending strength ratio mm in mm In NC23-31 79.4 3 1/8 31.8 1 1/4 9150 76.2 2.57:1 NC26-35 88.9 3 1/2 38.1 1 1/2 9150 82.9 2.42:1 NC31-41 104.8 4 1/8 50.8 2 9150 or 9450 100.4 2.43:1 NC35-47 120.7 4 3/4 50.8 2 9150 or 9450 114.7 2.58:1 NC38-50 127.0 5 57.2 2 1/4 9150 or 9450 121.0 2.38:1 NC44-60 152.4 6 57.2 2 1/4 9150 or 9450 144.5 2.49:1 NC44-60 152.4 6 71.4 2 13/16 9150 or 9450 144.5 2.84:1 NC44-62 158.8 6 1/4 57.2 2 1/4 9150 or 9450 149.2 2.91:1 NC46-62 158.8 6 1/4 71.4 2 13/16 9150 or 9450 150.0 2.63:1 NC46-65 165.1 6 1/2 57.2 2 1/4 9150 or 9450 154.8 2.76:1 NC46-65 165.1 6 1/2 71.4 2 13/16 9150 or 9450 154.8 3.05:1 NC46-47 171.4 6 3/4 57.2 2 1/4 9150 or 9450 159.5 3.18:1 NC50-67 171.4 6 3/4 71.4 2 13/16 9150 or 9450 159.5 2.37:1 NC50-70 177.8 7 57.2 2 1/4 9150 or 9450 164.7 2.54:1 NC50-70 177.8 7 71.4 2 13/16 9150 or 9450 164.7 2.73:1 NC50-72 184.2 7 1/4 71.4 2 13/16 9150 or 9450 169.5 3.12:1 NC56-77 196.8 7 3/4 71.4 2 13/16 9150 or 9450 185.3 2.70:1 NC56-80 203.2 8 71.4 2 13/16 9150 or 9450 190.1 3.02:1 6 5/8 REG 209.6 8 1/4 71.4 2 13/16 9150 or 9450 195.7 2.93:1 NC61-90 228.6 9 71.4 2 13/16 9150 or 9450 212.7 3.17:1 7 5/8 REG 241.3 9 1/2 76.2 3 9150 or 9450 223.8 2.81:1 NC70-97 247.6 9 3/4 76.2 3 9150 or 9450 232.6 2.57:1 NC70-100 254.0 10 76.2 3 9150 or 9450 237.3 2.81:1 8 5/8REG 279.4 11 76.2 3 9150 or 9450 266.7 2.84:1 8 5/8REG 355.6 14 76.2 3 9150 or 9450 266.7 2.84:1