Tool Flute Type

• Conventional spiral flutes can be used for drilling holes in a wide range of materials. Drill bits with conventional spiral flutes are used in a clockwise direction, which may also be called right-hand or right-handed. The helix angle ranges from 28 to 32 degrees.
• Fast spiral flutes have a higher helix angle than conventional spiral flutes, providing more efficient chip removal when drilling deep holes and when drilling materials that produce stringy chips, such as softer ferrous and non-ferrous materials. Drill bits with fast spiral flutes are used in a clockwise direction. The helix angle ranges from 35 to 45 degrees.
  
• Half round flutes have a straight cutting edge with no turns or twist in the flutes. The single flute results by removing half the body of the drill bit along its central axis, creating a half round appearance when viewed from the tip. Half round flutes are typically used in horizontal applications such as drilling on a lathe, because gravity will aid in pulling the chips out of the hole as it is being drilled. Drill bits with half round flutes are used in a clockwise direction. The helix angle is zero degrees.
  
• Left-hand fast spiral flutes have helical twists in the opposite direction and a higher helix angle than conventional spiral flutes, providing more efficient chip removal when drilling deep holes and when drilling materials that produce stringy chips, such as softer ferrous and non-ferrous materials. Drill bits with left-hand fast spiral flutes are used in a counterclockwise direction. The helix angle ranges from 35 to 45 degrees.
• Left-hand spiral flutes have helical twists in the opposite direction than conventional spiral flutes and can be used for drilling holes in a wide range of materials. Drill bits with left-hand spiral flutes are used in a counterclockwise direction. Left-handed spirals are commonly used with a reversible drill to assist with removal of broken fasteners. They can also be used in multiple spindle gear-driven drilling heads or screw machines. The helix angle ranges from 28 to 32 degrees.
• Parabolic spiral flutes have larger flutes than a fast spiral, providing increased space for efficient chip removal when drilling deep holes in a wide range of materials. Drill bits with parabolic spiral flutes are used in a clockwise direction. The helix angle ranges from 35 to 45 degrees.
  
• Slow spiral flutes have a lower helix angle than conventional spiral flutes. Slow spiral flutes provide efficient chip removal with high feed rates for shallow holes and in short-chipping materials such as brass, bronze, and cast iron. Drill bits with slow spiral flutes are used in a clockwise direction. The helix angle ranges from 10 to 20 degrees.
• Straight flutes have straight cutting edges with no twists in the flutes, providing efficient chip removal in materials that produce short chips such as in brass, other non-ferrous materials, and cast iron. Straight flutes, commonly used for horizontal drilling applications, prevent the drill bit from drawing or pulling itself into the material while drilling. Drill bits with straight flutes are used in a clockwise direction. The helix angle is zero degrees.