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