Contact Us
NDS Drilling Supply
26041 Newton Circle
Elko New Market, MN 55020
ndsdrillingsupply@gmail.com
1-800-637-1940
(952) 461-3400
(952) 461-3403 (fax)
26041 Newton Circle
Elko New Market, MN 55020
ndsdrillingsupply@gmail.com
1-800-637-1940
(952) 461-3400
(952) 461-3403 (fax)
optimum rotation speed
A good rule of thumb is to divide 300 by the bit diameter in inches to determine RPM. Here is a table of RPM with common bit sizes. Also, Feed Force (hold down and hold back) is the force required to feed a percussive tool properly is directly proportional to the level of output. 500 pounds of force per 1″ inch of hammer diameter. Please see below.
| BIT SIZE IN INCHES | PROPER RPM | FEED FORCE |
| 3-7/8 | 77.42 | 1,937.5 lbs. |
| 4-1/8 | 72.73 | 2,062.50 lbs. |
| 4-3/4 | 63.16 | 2,375 lbs. |
| 4-7/8 | 61.54 | 2,437.5 lbs. |
| 5 | 60 | 2,500 lbs. |
| 5-3/4 | 52.17 | 2,875 lbs. |
| 5-7/8 | 51.06 | 2,937.5 lbs. |
| 6 | 50 | 3,000 lbs. |
| 6-1/4 | 48 | 3,125 lbs. |
| 6-1/2 | 46.15 | 3,250 lbs. |
| 6-3/4 | 44.44 | 3,375 lbs. |
| 7 | 42.86 | 3,500 lbs. |
| 7-1/2 | 40 | 3,750 lbs. |
| 7-7/8 | 38.10 | 3,937.5 lbs. |
| 8 | 37.50 | 4,000 lbs. |
| 8-3/4 | 34.39 | 4,375 lbs. |
| 8-7/8 | 33.8 | 4,437.5 lbs. |
| 9 | 33.33 | 4,500 lbs. |
| 9-1/2 | 31.58 | 4,750 lbs. |
| 9-3/4 | 30.77 | 4,875 lbs. |
| 9-7/8 | 30.38 | 4,937.5 lbs. |
| 10 | 30 | 5,000 lbs. |
| 11-7/8 | 25.26 | 5,937.5 lbs. |
| 12 | 25 | 6,000 lbs. |
| 12-3/8 | 24.24 | 6,187.5 lbs. |
| 12-3/4 | 23.53 | 6,375 lbs. |