Percussion Drill Bit

The Percussion Drill Bit is what carries the piston energy to the rock face, therefore the condition of the bit cutting face should be well maintained. As the bit accumulates drill time the buttons and the steel will start to show a wear pattern. The pattern and rate of wear will depend greatly on the geological formation being drilled.

In soft formations the buttons on the drill bit may form a “snakeskin” effect on the surface, these surface cracks must be ground off to prevent bit failure. In hard formations where the bit wears quickly “flats” will be formed on the buttons. These flats should be ground away before they reach half the diameter of the button. Some formations wear away the steel of the percussion bit leaving the button exposed. The button must be ground down to prevent button failure. The following table indicates the recommended height of button bit exposed above the steel of the percussion bit.

Button Diameter Height of exposure
mm Inches mm Inches
11 7/16 6 1/4
12.5 1/2 7 9/32
14.5 9/16 8 5/16
15.8 5/8 9 3/8
19 3/7 13 1/2