Drilling

Drilling creates round holes by rotating a drill bit into a workpiece, delivering fast, repeatable holemaking with moderate tolerances and good throughput.

Overview

Drilling is a machining operation that produces cylindrical holes using a rotating drill and axial feed. It’s typically done on drill presses, CNC machining centers, or turning centers (for radial/axial holes), and often includes follow-on steps like countersinking, counterboring, or reaming.

Choose drilling when your part needs straight through-holes or blind holes quickly and economically, especially in prismatic parts, plates, and brackets. It scales well from prototypes to production with CNC drilling patterns and fixtures.

Tradeoffs: standard drilling leaves a tapered entry/exit burr and a rougher, less size-controlled bore than reaming/boring. Hole depth and chip evacuation drive cost and risk—deep holes need specialized tooling and coolant. True position, perpendicularity, and surface finish may require secondary operations or tighter fixturing.

Common Materials

  • Aluminum 6061
  • Steel 1018
  • Stainless Steel 304
  • Alloy Steel 4140
  • Titanium Grade 5
  • Brass C360

Tolerances

±0.003"

Applications

  • Bolt circle patterns in mounting plates
  • Dowel pin holes in fixtures
  • Tapped holes (drill + tap) in brackets
  • Cross-drilled ports in shafts
  • Fastener clearance holes in enclosures
  • Deep oil passages in hydraulic blocks

When to Choose Drilling

Drilling fits parts that need round holes in accessible locations with standard diameters and depths, where cycle time and cost matter more than ultra-tight bore size. It’s a strong choice for hole patterns, fastener features, and pre-holes for tapping or reaming in prototype through production volumes.

vs Milling

Choose drilling when the feature is a true round hole and you want the fastest cycle time with standard tools. Milling a hole (helical interpolation) makes sense for larger diameters or when you need better control over size without special drills, but it’s usually slower per hole.

vs Turning

Choose drilling when holes are needed in prismatic parts or off-axis locations that don’t justify turning setups. On lathe work, drilling is ideal for axial center holes, but turning/boring wins when you need tight concentricity to the OD or highly controlled internal diameters.

vs Grinding

Choose drilling for creating the hole geometry; grinding is typically a finishing process for size, roundness, and surface finish requirements drilling can’t hold. If the bore needs very tight tolerance, low Ra, or hardened-material accuracy, drill undersize and finish with a grinding/finishing operation.

vs Electrical Discharge Machining (EDM)

Choose drilling for speed and cost when the material is machinable and the hole doesn’t require extreme aspect ratio or sharp internal details. EDM is better for very hard materials, tiny holes, or difficult depths where tool pressure and chip evacuation make conventional drilling unstable.

vs Broaching

Choose drilling for round holes and flexible diameters with low tooling commitment. Broaching makes sense for high-volume internal profiles (like keyways or splines) after a pre-drilled hole, but it requires dedicated broaches and consistent production demand.

Design Considerations

  • Call out hole type clearly (THRU, blind depth, spotface/counterbore/countersink) and reference the correct datum scheme for position tolerances
  • Keep depth-to-diameter reasonable; if you need deep holes, specify whether deep-hole drilling is acceptable and allow extra tolerance/cost
  • Avoid specifying ultra-tight hole size on a drilled hole; use ream/boring callouts when you truly need a precision bore
  • Provide adequate edge distance and web thickness to reduce breakout, burrs, and distortion during drilling
  • Standardize hole diameters and use common drill sizes to reduce tool changes and cycle time
  • Specify burr requirements (break edge, deburr both sides) so quoting includes the finishing time