What is deep hole drilling?
A deep hole is defined by its depth to diameter ratio (D:d), typically greater than 10:1. Gundrilling is a precision process to drill deep holes in a variety of materials, from aluminum to superalloys. Good finish, tight diameter control and straight-ness are part of the finished process.
Advances in technology allow common CNC machining centers, equipped with high pressure through-spindle coolant, to be capable of gundrilling.
Holes deeper than 20:1 generally require a dedicated gundrilling machine to achieve highest productivity and process reliability.
UNISIG produces the most capable deep hole drilling machines on the market, with applications exceeding 400:1 depth to diameter ratio.
Drilling Process
Rotating Tool
- Typically used for non-symmetrical components or round parts requiring holes offcenter
- Cutting speed is determined by tool spindle speed
- Drill drift can be significant compared to rotating workpiece or counter-rotating process
Rotating Workpiece
- Used for round parts with a deep hole on-center
- Cutting speed is determined by part, balanced to allow high rotating speeds
- Drill drift is reduced compared to rotating tool only
Counter-rotating Tool and Workpiece
- Used for round parts with a deep hole on-center
- Cutting speed determined by combination of tool and workpiece rotation
- Provides best hole straightness and concentricity compared to rotating workpiece or rotating tool
Drilling Tools
Gundrill Tooling
- Small diameter drilling, typically 1 - 50mm [0.04 -2.00in] diameter holes
- High-pressure coolant is introduced through the spindle and gundrill center
- Chips are discharged on the outside of the tool
- Special forms can be ground in tool tip
BTA/STS tooling
- Larger diameter drilling, typically 20 - 200mm [0.79 - 8 inch]
- Counter-boring and trepanning tools cover larger range, up to 500mm [20 inch] diameter
- High-pressure coolant is introduced around the outside of the tool
- Chips are discharged through the tool center and machine spindle
- High penetration rates and power requirements compared to gundrill tooling
