Gun drilling is a specialized technique for producing deep, narrow holes. The name comes from its origins in firearm manufacturing, where it was used to bore long, straight barrels. Over time, other industries adopted the method for its consistency and precision.
The primary purpose of gun drilling is to create deep, slender holes that are exceptionally straight and dimensionally accurate. It works well in metals, plastics, and other materials, allowing manufacturers to produce high-quality components reliably(Ruomu, 2025).
Notable features of gun drilling:
- Exceptional accuracy: Produces very straight holes with tight tolerances that many other methods can’t match.
- High depth-to-diameter capability: Can achieve extremely large depth-to-diameter ratios—sometimes as high as 300:1.
- Integrated coolant flow: Delivers coolant directly to the cutting edge to prevent overheating and flush chips, resulting in a smoother finish.
- Purpose-built tooling: Uses long, slender gundrills designed for efficient cutting and chip evacuation.
If your hole is 300x deeper than its diameter, you’re not drilling—you’re gun drilling. This specialized process is the secret to manufacturing critical components from fuel injectors to surgical tools. What’s the highest depth-to-diameter ratio you’ve successfully achieved, and what material was it?
