Success at drilling deep holes depends less on power and more on control. A long bit that wanders even slightly at the surface can exit far off target, so getting the start right is everything.
Why Deep Holes Wander
The deeper a bit travels, the more small errors compound. Any flex in a long bit, any hard grain or inclusion in the material, and any misalignment at the entry all push the tip off course. Because you cannot see or correct the path once the bit is buried, the fix has to happen before and during the first inch of drilling.
Start With a Pilot Hole
A short, accurate pilot hole drilled with a stubby bit creates a precise track for your longer bit to follow. Because a stiff, short bit resists deflection, it establishes the true line. Your extra-length bit then drops into that channel and is far less likely to drift. This single step solves most wandering problems.
- Centre-punch: Mark metal with a punch so the bit cannot skate.
- Stubby pilot: Drill an accurate shallow hole first to guide the long bit.
- Check alignment: Sight the drill against a square from two directions.
Peck Drilling Keeps You Straight
Rather than pushing straight through, drill in stages. Advance the bit a short distance, then withdraw it fully to clear the chips before going deeper. This peck-drilling rhythm prevents the flutes from packing with swarf, which is a major cause of binding, overheating and deflection in deep holes.
Choose the Right Long Bit
Deep holes call for the right tool. Extra-length twist drills reach where standard bits cannot, while bell-hanger bits are purpose-built for running wire through walls and studs, often with a hole in the tip for pulling cable. American-made long-series bits are ground for straightness and hold their line better than budget alternatives.
- Extra-length drills: For deep holes in wood, metal and general stock.
- Bell-hanger bits: Long, flexible bits ideal for wiring and installation work.
- Steady speed: Moderate RPM with light, consistent pressure.
Support and Patience
Keep the workpiece firmly clamped and let the bit set its own pace. Forcing a long bit is the fastest way to bend it off line or snap it. With a good pilot, regular pecking and a quality long bit, straight deep holes become routine.