Principle of rock breaking

1.Typical problems in percussive drilling

1.1  Percussion

Too high:

-     Button breakages

-     Drill steel / Shank breakages

Too low:

-     Low penetration rate

-     Excessive button wear (due to rotation breaking the rock)

-> percussion measure settings are always compromise between penetration rate and drill steel economy

1.2  Feed

Too high:

-     Problems in flushing

-     Rapid button / body wear

-     Increased hole deviation

-     Problems in uncoupling

-     Bending of drill steel and shank -> breakages

Too low:

-     Button pop-outs

-     Poor penetration rate

-     Loose couplings and excessive thread wear

-     Poor energy transmission

1.3  Rotation

Too high:

-     Recutting and low penetration rate

-     Excessive bit wear (since the rock is forced to break by rotation instead of percussion)

-     Uncoupling is difficult

Too low:

-     Low penetration rate

-     Energy is lost for recutting

1.4  Flushing

Too high:

-     Unnecessary energy loss at the compressor

-     In waterflushing water enters into the drifter if sealing is broken

Too low:

-     Low penetration rate (increased recutting)

-     Excessive bit wear

-     Bit jamming