When drilling, the speed has a great influence on the drilling speed of different rock formations. For argillaceous rocks, the penetration speed is proportional to the rotational speed;

 

In hard, abrasive rock, drilling speed increases with increasing rotational speed, but at a slower rate;

 

When the rotational speed continues to increase beyond the limit rotational speed, the main reason for the decrease in drilling speed is that the core drill bit wears too quickly and cracks fully develop because the rotational speed is too high;

 

For medium-hard, low-wear rocks, the RPM and coring bit RPM are somewhere in between.

 

For rocks that are developing cracks, due to the uneven bottom of the hole, the rotation speed should be appropriately reduced to prevent early cracking. In addition, drilling depth, drilling equipment, and drilling tool strength will also affect the rotation speed.