Gun drill
A gun drill is a specialized type of drill bit and drilling process used primarily for creating deep, straight, and accurate holes in metal. Unlike conventional twist drills, gun drills are designed with a single cutting edge at the tip and a long, slender body featuring a v-shaped flute along its length for chip evacuation and coolant delivery.
The drilling process itself, often referred to as "gun drilling," utilizes high-pressure coolant delivered internally through the drill body to flush chips away from the cutting edge and lubricate the cutting zone. This efficient chip removal prevents chip packing, which can lead to tool breakage and poor hole quality. The coolant also helps to control temperature, further contributing to accuracy and extended tool life.
Gun drills are typically used on specialized machinery that provides precise control over feed rate, spindle speed, and coolant pressure. These machines often incorporate features to maintain alignment and minimize vibration, which are critical for achieving the desired hole characteristics.
The applications for gun drilling are diverse, including manufacturing firearm barrels (hence the name), hydraulic manifolds, fuel injectors, and other components requiring precise deep holes. Materials commonly gun drilled include steel, stainless steel, aluminum, and various alloys.
Key advantages of gun drilling over other drilling methods include:
- High Length-to-Diameter Ratio: Capable of drilling holes with length-to-diameter ratios exceeding 20:1 and even reaching 300:1 in some cases.
- Excellent Straightness and Roundness: Produces holes with minimal deviation from the desired straightness and roundness.
- Superior Surface Finish: Creates a smooth, high-quality surface finish inside the hole.
- Close Tolerances: Allows for the creation of holes with tight dimensional tolerances.
Despite these advantages, gun drilling can be a more complex and expensive process compared to conventional drilling. The need for specialized equipment, skilled operators, and potentially longer cycle times contributes to the overall cost. Therefore, it's typically reserved for applications where the unique capabilities of gun drilling are essential.