Drilling Guide
Peck Drilling Explained
Why deep holes need a different technique to shallow ones, and how much extra time to budget for it.
To peck drill is to drill a hole in short stages, retracting between cuts to break or clear chips. 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
The calculator’s 10–15% allowance is only a rough estimate, not a guaranteed cycle-time increase. Each retract and re-entry adds travel time, so actual overhead depends on peck count, retract distance, rapid speed and controller settings. 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.
Peck drilling G-code: G83 vs G73
G83 is a full-retract deep-hole peck cycle: the drill returns to the R plane above the hole after each peck to clear chips to the top. G73 is a high-speed, chip-break peck cycle with a small retract; chips remain in the hole, so it is unsuitable when they must be lifted out completely.
This illustrative line assumes millimetres, absolute positioning and a work surface at Z0: drill to Z−20, retract to R2 and use a feed of 80 mm/min. Q2 specifies a 2 mm peck depth on controls using this convention. Set the tool, spindle, coolant and positioning modes first; check your controller manual for Q units, retract behaviour and G98/G99 return levels, then cancel the cycle with G80.
Choosing peck depth by material
For a conventional twist drill, trial pecks around 1× diameter in mild steel, and shorter pecks around 0.5× diameter in stringy aluminium, stainless or titanium, can be conservative starting points. Shorten them as chip evacuation becomes difficult. These are trial settings, not universal limits: drill geometry, coolant delivery and the tool supplier's instructions take priority. Use the drill speed chart for an initial RPM and the drilling calculator to estimate feed and time.
Practical tips
- Choose peck depth for the material and chip evacuation; shorten each stage as the hole deepens.
- 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?
Each retract and re-entry adds time. The calculator’s 10–15% allowance is a rough estimate; deep holes or short pecks may add substantially more.
What is a good peck depth?
Start with the drill supplier’s guidance. For conventional twist drills, trial around 1× diameter in mild steel or 0.5× diameter in stringy materials, then shorten pecks if chips pack or evacuation slows.
Does peck drilling reduce tool life?
Clearing trapped chips can protect the drill, but excessive pecking, rubbing on re-entry or dwelling at the bottom can accelerate wear. Maintain positive cutting feed and use a cycle suited to the drill and coolant supply.