Percussion Drilling Fundamentals

What are the elements of percussive drilling?

• Blasting

• Percussion

• Feed

• Flushing

• Rotation

What is indexing distance?

• The distance the drill bit rotates during one revolution.

• The distance between drill bit buttons.

• The distance the drill bit rotates before the next percussion occurs.

• The depth the drill bit travels during percussion.

What is the formula for the speed of rotation of a drill bit?

What is the name of the material used to make the drill bit buttons? Why are we using this kind of material? Please refer to the image.

• Copper. It is the strongest material.

• Diamond. Has the greatest hardness.

• Tungsten carbide. Has a very low thermal expansion.

• Steel. Scrapes rocks with ease.

What is the flushing pressure?

• 10-15 psi

• 8-13 bar

• 7-15 bar

• 10-15 bar

What is the rotation pressure?

• 60-70 psi

• 50-70 bar

• 45-70 atm

• 50-75 bar

What is the percussion pressure?

• 185 -210 bar

• 160-200 bar

• 188-230 bar

• 190-201 psi

What is the feed pressure?

• 95 bar

• 90 bar

• 90 psi

• 85 atm

What is the consequence of high feed pressure?

• Bending of drill steel and hole deviation.

• Bending of wheel tyres and machines chassis.

• Machine moves backwards.

• Bending of the booms and damage to driver cabin.

What are the components of the drill string?

• Drill bit

• Rotation

• Drill steel

• Shank

• Coupling