CNC Machining Drilling Time Calculator
Created by: Ethan Brooks
Last updated:
Calculate cutting time per hole and planned drilling cycle time with explicit peck, dwell, rapid and tool-change allowances.
CNC Machining Drilling Time Calculator
CNC MachiningCalculate cutting time per hole and planned drilling cycle time with explicit peck, dwell, rapid and tool-change allowances.
What does this calculator do?
A drilling time calculator estimates how long a planned group of holes takes by separating cutting travel from non-cut events. The cutting portion uses total feed travel, spindle speed and feed per revolution. Additional fields account for explicitly entered peck interruptions, dwell, positioning or rapid movement, and a tool-change allowance for the complete operation. The output shows penetration rate, cutting time per hole and total planned minutes.
This separation makes the estimate easier to check against a program. A hole’s drawing depth is not always the distance traveled at cutting feed. Approach, drill-point geometry, breakthrough and any repeated feed movement may add travel. The calculator therefore asks for total feed travel rather than guessing a depth allowance from drill diameter. Every length that is included should correspond to a defined movement in the intended cycle.
Peck drilling needs equally clear boundaries. Here, peck count means extra interruption events per hole, with a measured or planned non-cut duration for each event. It is not a control-specific peck depth or an inferred retract schedule. Repeated movement at cutting feed belongs in total feed travel; movement assigned to the peck time must not be counted again elsewhere. Total dwell and other positioning time are entered separately per hole.
The result is useful for preliminary scheduling, estimating and comparison with observed cycle data. It is not a prediction of a machine controller’s acceleration or a recommendation for a drill, feed or peck cycle. Tool condition, material, hole depth, chip evacuation, coolant and workholding determine what a workable process requires. Those decisions must precede interpretation of the time estimate.
How the calculation works
Feed per revolution multiplied by spindle revolutions per minute gives penetration rate in length per minute. Divide the total feed travel per hole by that penetration rate to obtain cutting minutes per hole, then multiply by the whole hole count. This is a constant-feed model; it assumes the entered RPM and feed represent the cutting movement being timed.
For non-cut time, multiply extra peck events by seconds per event. Add total dwell seconds and other rapid or positioning seconds per hole, then multiply that sum by the number of holes. Add the operation’s total tool-change seconds once and divide by 60. Planned operation minutes equal cutting minutes plus these non-cut minutes.
Zero is valid for allowances that are deliberately excluded, but not for cutting travel, RPM or feed. Hole count must be a positive whole number and peck events a nonnegative whole number. Unit conversion changes entered travel and feed per revolution together, leaving physical cutting time invariant.
Formula and symbols
vf = fn×n; cutting = holes×travel/vf; non-cut = [holes×(pecks×peckSeconds+dwellSeconds+rapidSeconds)+toolChangeSeconds]/60; total = cutting+non-cut.
- fn, n, travel: Feed per revolution, RPM and total feed travel per hole
- pecks: Extra non-cut interruption events per hole
- allowances: Explicit seconds for pecks, total dwell per hole, other rapid per hole and operation tool changes
How to use this calculator
- Define travel. Enter whole holes and total movement at cutting feed, including any actual approach or breakthrough travel.
- Enter the drilling feed. Provide constant RPM and programmed feed per revolution.
- Account for events once. Enter peck, dwell, rapid and operation tool-change allowances without double counting.
- Check the time boundary. Review cutting versus non-cut minutes and verify the estimate with the actual cycle.
Worked examples
Example 1
Basic drilling: ten holes each have 24 mm total feed travel, a programmed 1,200 RPM and 0.1 mm/rev feed. Penetration is 120 mm/min, so cutting takes 0.2 minutes per hole and 2 minutes for all ten. If every non-cut field is zero, the reported operation time is 2 minutes. This is explicitly a cutting-only scenario, not evidence that loading, positioning and retracts consume no machine time.
Example 2
Add allowances: keep that case and enter two extra peck events per hole, three seconds per event, one second total dwell, four seconds other rapid time and 30 seconds of tool-change time for the operation. Per-hole non-cut time is 11 seconds. Ten holes plus the tool change total 140 seconds, or 2.3333 minutes. Planned operation time becomes 4.3333 minutes.
Example 3
Travel correction: if an additional 6 mm per hole is genuinely traveled at cutting feed, total feed travel becomes 30 mm. At 120 mm/min, cutting time increases to 0.25 minutes per hole and 2.5 minutes for ten holes. Keep the earlier 2.3333-minute non-cut allowance only if that extra travel was not already represented there; the revised total is then 4.8333 minutes. Recording this boundary makes the additional half-minute explainable to another estimator who reviews the original and revised schedules.
Practical applications
- Quoting a hole pattern: separate the productive feed movement from repeated positioning and tool-change allowances. This makes it easier to see which assumptions drive the estimate for a short or long run.
- Program comparisons: compare two planned cycles using their actual travel and event timing. A shorter nominal depth does not necessarily imply a shorter operation when pecks and retracts differ.
- Machine observation: record actual non-cut durations and replace preliminary allowances after a controlled run. Keep the same definitions so an apparent improvement is not merely a change in counting boundaries.
- Batch planning: vary whole hole count while retaining a single operation-level tool-change allowance. This exposes the difference between repeated per-hole time and a fixed event charged only once.
- Feed audits: compare the programmed feed per revolution with penetration rate at the entered RPM. This is useful when a control display or process sheet expresses feed in length per minute instead.
- Training and handoff: export the equations, source basis and counted events with the result. Another person can then distinguish cutting-only minutes from complete planned operation minutes without reconstructing hidden assumptions. Keep the resulting record with the program revision and measured event timings so a later comparison uses the same operation boundary and counting conventions.
Tips for a useful estimate
Write down the start and end of the timed operation before entering allowances. Decide whether final retract, indexing and tool change are inside that boundary, then count each once. Use total dwell per hole rather than inadvertently multiplying it by peck count again.
Confirm whether a repeated motion is at cutting feed or rapid. Add feed movement to total travel, and put measured non-cut movement in the appropriate time field. Do not derive rapid time from distance alone when acceleration and controller behavior matter.
Treat zero allowances as explicit exclusions. Replace preliminary timing with measured values when available, and retain the tool, material, coolant, program revision and measurement basis with the estimate.
Frequently asked questions
Should I enter hole depth or total travel?
Enter total travel performed at the entered cutting feed for one hole. Drawing depth may omit approach, point or breakthrough travel, and some cycles repeat feed movement. Determine those distances from the intended cycle and geometry. The calculator does not invent drill-point compensation or an allowance from diameter, because those details depend on the tool and operation.
How does the peck allowance work?
Enter the number of extra peck interruptions per hole and the non-cut seconds for each event. The model multiplies those quantities; it does not create a peck schedule from depth. Include repeated cutting-feed travel in the travel field instead. Clear event definitions prevent a retract, dwell or re-entry from being charged in two different places.
Is the tool-change time per hole?
No. That field is one total allowance for the complete operation being estimated. If the schedule contains several tool changes, enter their combined seconds. The per-hole fields are separately multiplied by hole count. This distinction matters for small batches, where spreading or repeating a fixed tool change incorrectly can substantially distort the quoted time.
Does the calculator model acceleration?
No. Penetration rate is treated as constant during entered feed travel. Rapid acceleration, deceleration, control look-ahead and cycle implementation are outside the model. Use observed event timing or a verified machine simulation for the non-cut allowances. Very short holes and frequent interruptions may make these omitted dynamics especially important to the difference between estimate and observed time.
Can the drilling feed be recommended automatically?
This tool does not select feed or RPM. Enter values appropriate to the actual drill, material, hole and process from a named source or program being reviewed. The resulting time is conditional on those inputs. Tool strength, coolant delivery, chip evacuation and workholding remain separate decisions that a timing equation cannot establish.
Why does changing units keep time the same?
Converting both total travel and feed per revolution preserves their physical relationship. Spindle speed remains revolutions per minute, so penetration rate changes its displayed length unit while cutting minutes stay equivalent. If a manual conversion changes only travel or only feed, the estimate will be inconsistent. The unit switch converts both entered measurements together.
Sources and scope
- Sandvik Coromant: Formulas and definitions for drilling — metric. Reference sheet; publication date not stated. Page H81, penetration rate. Penetration rate vf = fn × n; travel divided by constant penetration rate gives cutting minutes. Accessed 2026-09-22.
- NIST: NIST Guide to the SI, Appendix B.9. SP 811 conversion factors. Length conversion factors. Defines the exact international inch conversion used to keep metric and US calculations equivalent. Accessed 2026-09-21.
References support the stated method and scope. Application-specific values remain explicit inputs; no proprietary cutting-data tables or generic recommendations are embedded.