Rockbit "Weight on Bit" and "RPM" Operating Suggestions
The tables below give you the suggested pulldown force for drilling with different size rotary bits.
4-1/2" API Regular Pin Connection
| Weight on Bit per Inch of Bit Diameter | Total Suggested Weight on Bit (Pulldown Force) | |||||
| IADC Class | RPM | Low | High | 6 3/4" Bit | 7 7/8" Bit | 8" Bit |
| 1-1 to 1-4 | 70 to 120 | 1,000 | 3,000 | 20,250 | 23,625 | 24,000 |
| 2-1 to 2-4 | 60 to 100 | 3,000 | 5,000 | 33,750 | 39,375 | 40,000 |
| 3-1 to 3-4 | 60 to 80 | 4,000 | 7,000 | 47,250 | 55,125 | 56,000 |
| 4-1 to 4-4 | 50 to 150 | 1,000 | 5,000 | 33,750 | 39,375 | 40,000 |
| 5-1 to 5-4 | 50 to 150 | 3,000 | 6,500 | 43,875 | 51,188 | 52,000 |
| 6-1 to 6-4 | 50 to 120 | 4,000 | 7,000 | 47,250 | 55,125 | 56,000 |
| 7-1 to 7-4 | 50 to 90 | 4,000 | 8,000 | 54,000 | 63,000 | 64,000 |
| 8-1 to 8-4 | 40 to 80 | 6,000 | 9,000 | 60,750 | 70,875 | 72,000 |
4-1/2" API Regular Pin Connection
| Weight on Bit per Inch of Bit Diameter | Total Suggested Weight on Bit (Pulldown Force) | ||||
| IADC Class | RPM | Low | High | 8 1/2" Bit | 9" Bit |
| 1-1 to 1-4 | 70 to 120 | 1,000 | 3,000 | 25,500 | 27,000 |
| 2-1 to 2-4 | 60 to 100 | 3,000 | 5,000 | 42,500 | 45,000 |
| 3-1 to 3-4 | 60 to 80 | 4,000 | 7,000 | 59,500 | 63,000 |
| 4-1 to 4-4 | 50 to 150 | 1,000 | 5,000 | 42,500 | 45,000 |
| 5-1 to 5-4 | 50 to 150 | 3,000 | 6,500 | 55,250 | 58,500 |
| 6-1 to 6-4 | 50 to 120 | 4,000 | 7,000 | 59,500 | 63,000 |
| 7-1 to 7-4 | 50 to 90 | 4,000 | 8,000 | 68,000 | 72,000 |
| 8-1 to 8-4 | 40 to 80 | 6,000 | 9,000 | 76,500 | 81,000 |
6-5/8" API Regular Pin or BECO Connection
| Weight on Bit per Inch of Bit Diameter | Total Suggested Weight on Bit (Pulldown Force) | |||||
| IADC Class | RPM | Low | High | 9 7/8" Bit | 10 5/8" Bit | 11" Bit |
| 1-1 to 1-4 | 70 to 120 | 1,000 | 3,000 | 29,625 | 31,875 | 33,000 |
| 2-1 to 2-4 | 60 to 100 | 3,000 | 5,000 | 49,375 | 53,125 | 55,000 |
| 3-1 to 3-4 | 60 to 80 | 4,000 | 7,000 | 69,125 | 74,375 | 77,000 |
| 4-1 to 4-4 | 50 to 150 | 1,000 | 5,000 | 49,375 | 53,125 | 55,000 |
| 5-1 to 5-4 | 50 to 150 | 3,000 | 6,500 | 64,188 | 69,063 | 71,500 |
| 6-1 to 6-4 | 50 to 120 | 4,000 | 7,000 | 69,125 | 74,375 | 77,000 |
| 7-1 to 7-4 | 50 to 90 | 4,000 | 8,000 | 79,000 | 85,000 | 88,000 |
| 8-1 to 8-4 | 40 to 80 | 6,000 | 9,000 | 88,875 | 95,625 | 99,000 |
6-5/8" API Regular Pin or BECO Connection
| Weight on Bit per Inch of Bit Diameter | Total Suggested Weight on Bit (Pulldown Force) | |||||
| IADC Class | RPM | Low | High | 11 1/2" Bit | 12 1/4" Bit | 13 3/4" Bit |
| 1-1 to 1-4 | 70 to 120 | 1,000 | 3,000 | 34,260 | 36,750 | 41,250 |
| 2-1 to 2-4 | 60 to 100 | 3,000 | 5,000 | 57,100 | 61,250 | 68,750 |
| 3-1 to 3-4 | 60 to 80 | 4,000 | 7,000 | 79,940 | 85,750 | 96,250 |
| 4-1 to 4-4 | 50 to 150 | 1,000 | 5,000 | 57,100 | 61,250 | 68,750 |
| 5-1 to 5-4 | 50 to 150 | 3,000 | 6,500 | 74,230 | 79,625 | 89,375 |
| 6-1 to 6-4 | 50 to 120 | 4,000 | 7,000 | 79,940 | 85,750 | 96,250 |
| 7-1 to 7-4 | 50 to 90 | 4,000 | 8,000 | 91,360 | 98,000 | 110,000 |
| 8-1 to 8-4 | 40 to 80 | 6,000 | 9,000 | 102,780 | 110,250 | 123,750 |
6-5/8" API Regular Pin or BECO Connection
| Weight on Bit per Inch of Bit Diameter | Total Suggested Weight on Bit (Pulldown Force) | |||||
| IADC Class | RPM | Low | High | 15" Bit | 16" Bit | 17 1/2" Bit |
| 1-1 to 1-4 | 70 to 120 | 1,000 | 3,000 | 45,000 | 48,000 | 52,500 |
| 2-1 to 2-4 | 60 to 100 | 3,000 | 5,000 | 75,000 | 80,000 | 87,500 |
| 3-1 to 3-4 | 60 to 80 | 4,000 | 7,000 | 105,000 | 112,000 | 122,500 |
| 4-1 to 4-4 | 50 to 150 | 1,000 | 5,000 | 75,000 | 80,000 | 87,500 |
| 5-1 to 5-4 | 50 to 150 | 3,000 | 6,500 | 97,500 | 104,000 | 113,750 |
| 6-1 to 6-4 | 50 to 120 | 4,000 | 7,000 | 105,000 | 112,000 | 122,500 |
| 7-1 to 7-4 | 50 to 90 | 4,000 | 8,000 | 120,000 | 128,000 | 140,000 |
| 8-1 to 8-4 | 40 to 80 | 6,000 | 9,000 | 135,000 | 144,000 | 157,500 |
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