CNC Drilling

CNC drilling creates accurate, repeatable holes using programmed machine tools, supporting high hole counts, controlled patterns, and tight positional accuracy across many materials.

Overview

CNC drilling (CNC holemaking) uses a CNC mill or drill/tap center to produce holes to defined diameters, depths, and locations using programmed cycles (spot, drill, peck, ream, countersink/counterbore). It excels at repeatability, pattern accuracy, and running many holes per part with consistent results.

Choose CNC drilling for plates, brackets, housings, and components where hole location and perpendicularity matter, or where you need secondary hole features (reamed fits, tapped holes, countersinks). It handles prototypes through production; the value increases with higher hole counts and tighter location requirements.

Tradeoffs: drilling alone won’t hold tight diameter like reaming/boring, and deep or high aspect-ratio holes drive cycle time, tool wear, and chip evacuation risk. Cross-holes, angled surfaces, and thin walls can cause drift and burrs, so add spotting, appropriate drills, and deburring plans.

Common Materials

  • Aluminum 6061
  • Steel 1018
  • Stainless 304
  • Stainless 17-4 PH
  • Brass 360
  • Titanium Ti-6Al-4V

Tolerances

±0.002"

Applications

  • Bolt-hole patterns in machined plates
  • Tapped mounting holes in housings
  • Dowel pin holes (reamed) for alignment
  • Countersunk holes for flat-head fasteners
  • Cross-drilled ports in manifolds
  • Jig and fixture base plates

When to Choose CNC Drilling

CNC drilling fits parts with defined hole patterns, moderate depths, and requirements for consistent location and perpendicularity. It’s a strong choice when a part needs many holes, mixed hole types (drill/ream/tap/countersink), and repeatability from prototype to production.

vs Deep Hole Drilling

Choose CNC drilling when hole depths are moderate and you need many features in one setup—drill/ream/tap/countersink—with tight positional control. Deep hole drilling is better when the primary requirement is very high depth-to-diameter holes where chip evacuation and straightness dominate the process choice.

vs Manual drilling (drill press)

Choose CNC drilling when hole-to-hole spacing, true position, and repeatability matter, or when you have larger hole counts that benefit from programmed cycles. Manual drilling is harder to control for pattern accuracy and is typically slower and less consistent across batches.

vs CNC milling with interpolation (circular milling)

Choose CNC drilling for standard hole sizes where speed and tool life are priorities, especially for high hole counts. Interpolation makes sense for larger diameters, tighter diameter control, or when you need to hit a nonstandard size without a dedicated drill/reamer.

vs Laser cutting (holes in sheet)

Choose CNC drilling when you need accurate, round holes with controlled edge quality, countersinks/counterbores, or holes after forming/machining. Laser-cut holes can be limited by taper, heat-affected edge condition, and difficulty adding 3D hole features.

Design Considerations

  • Call out hole function (clearance, tap, ream, dowel) and specify class/fit so the shop selects drill vs ream vs bore correctly
  • Avoid extreme depth-to-diameter ratios unless necessary; add relief or redesign to reduce depth and improve chip evacuation
  • Spot or chamfer hole starts, especially on angled or curved surfaces, to prevent drill walk and location error
  • Minimize unique hole diameters and thread sizes to reduce tool changes and cycle time
  • Specify true position requirements only where needed; tight location tolerances drive inspection time and fixturing effort
  • Plan for burr control by adding edge-break requirements and identifying critical no-burr surfaces