page_title: Drilling
section_title: Deep hole drilling
hierarchical_section_title: Drilling / Process / Deep hole drilling
caption_attribution_description: English: Close up of drilled blast-hole at Rixö abandoned granite quarry, Lysekil Municipality, Sweden. Photo is taken just before sunset when the light saturates the color of the rocks. This kind of granite is full of large crystals that reflects the light and any part of these rocks sparkle in the sun. Svenska: Närbild av ett av spänghålen i Rixös övergivna granitbrott i Lysekils kommun, Sverige. Bilden är tagen just innan solnedgången när ljuset mättar färgen på klipporna. Den här graniten är full av större kristalller som reflekterar ljuset och får klipporna att glittra i solen.
context_page_description: Drilling is a cutting process that uses a drill bit to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at rates from hundreds to thousands of revolutions per minute. This forces the cutting edge against the work-piece, cutting off chips from the hole as it is drilled.
  In rock drilling, the hole is usually not made through a circular cutting motion, though the bit is usually rotated. Instead, the hole is usually made by hammering a drill bit into the hole with quickly repeated short movements. The hammering action can be performed from outside the hole or within the hole. Drills used for horizontal drilling are called drifter drills.
  In rare cases, specially-shaped bits are used to cut holes of non-circular cross-section; a square cross-section is possible.
context_section_description: Deep hole drilling is defined as drilling a hole of depth greater than ten times the diameter of the hole. These types of holes require special equipment to maintain the straightness and tolerances. Other considerations are roundness and surface finish.
  Deep hole drilling is generally achievable with a few tooling methods, usually gun drilling or BTA drilling. These are differentiated due to the coolant entry method (internal or external) and chip removal method (internal or external). Using methods such as a rotating tool and counter-rotating workpiece are common techniques to achieve required straightness tolerances. Secondary tooling methods include trepanning, skiving and burnishing, pull boring, or bottle boring. Finally, a new kind of drilling technology is available to face this issue: vibration drilling. This technology breaks up the chips by a small controlled axial vibration of the drill. The small chips are easily removed by the flutes of the drill.
  A high tech monitoring system is used to control force, torque, vibrations, and acoustic emission.  Vibration is considered a major defect in deep hole drilling which can often cause the drill to break. A special coolant is usually used to aid in this type of drilling.
caption: Blast hole several meters long, drilled in granite
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