1) Down the Hole hammer: Percussion is done at the bottom of the hole, allowing a constant drilling speed rate and straighter hole than other methods.Down the hole hammers are powered by compressed air. This method is suitable for medium to big sized holes from medium to high depths.
2 & 3) Top Hammer (drifter). Hydraulically or pneumatically powered top hammers are available, percussion energy (impact energy) is lost as each rod is added thus getting a slower drilling rate as depth increases. These methods are suitable for small to medium sized holes to medium depths.