Drilling Guide
Peck Drilling Explained
Why deep holes need a different technique to shallow ones, and how much extra time to budget for it.
Drill deep enough and chips stop clearing on their own — they pack into the flutes, build up pressure, and either snap the drill or ruin the finish. Peck drilling solves this by breaking the cut into stages with full retractions in between.
Estimate the real drilling time
The drill time calculator already builds in a peck drilling allowance — adjust it to match your setup.
What peck drilling actually does
Instead of feeding the drill straight through to full depth in one continuous pass, peck drilling advances a set distance, then retracts the drill fully out of the hole before going back in for the next stage. That full retraction clears chips out of the flutes and off the cutting edge, preventing the pack-up that causes binding, overheating and snapped bits on deep holes.
When you need it
As a rule of thumb, holes deeper than about 3× the drill diameter benefit from peck drilling — beyond that ratio, chips increasingly struggle to clear the flutes under their own momentum. Softer, more stringy materials like aluminium tend to need it sooner than free-machining steels, since their chips are less likely to break cleanly.
How much time to add
A peck allowance of roughly 10-15% is typical for moderately deep holes, covering the extra retract-and-re-enter cycles. Very deep holes, or materials prone to long stringy chips, may need a higher allowance — see the speeds and feeds guide for the base feed rate this percentage is applied to.
Practical tips
- Peck depth is usually 1-3× the drill diameter per stage — shorter pecks for stringier materials or smaller drills.
- A brief pause at full retraction lets any trapped chips fall clear before re-entering.
- CNC controls typically offer a dedicated peck (G83) or high-speed peck (G73) cycle rather than requiring manual retraction.
Frequently asked questions
What is peck drilling?
A technique for deep holes where the drill periodically retracts fully out of the hole to clear chips, rather than drilling straight through in one continuous pass.
When do I need to peck drill?
Generally once hole depth exceeds about 3× the drill diameter, since chips can no longer clear the flutes reliably beyond that point.
How much extra time does peck drilling add?
Typically 10-15% on top of the straight-line drilling time, to account for retract and re-entry cycles.