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Deep Hole Drilling Services

Our deep hole drilling services hold fit-critical bores to ±0.005 mm past an L/D of 10:1. Gundrilling or BTA tooling is matched to each bore, from one prototype to production.

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  • ±0.005 mm

    Fit-Critical Bores

  • ~1000 mm

    Workpiece Length

  • 3 Days

    First Articles

Gundrill boring a deep hole in a steel cylinder on CNC lathe
ISO Certified ISO 9001, ISO 13485, AS9100D
Long cylinder body with deep straight bore on dark worktable

Long Bore Machining for Custom CNC Parts

Once a hole’s depth passes roughly 10 times its diameter (L/D >10:1), standard drilling loses straightness, generates heat and drifts off-center. DEK matches single-flute gundrill tooling or external-coolant BTA boring bars to the bore’s ratio and material.

Deep bores run inside full CNC machining programs, from a single prototype bore to a production run. Because gundrilling and BTA differ in coolant path, the right choice depends on bore diameter and length; talk with our engineers to have your bore reviewed.

Why Source Deep Holes Through DEK

Deep hole drilling rarely stands alone. Here is why engineers keep the bore and the rest of the part under one roof.

  • One Quality System

    Milling, turning, EDM and grinding around the bore run under the same documented QMS, certified to ISO 9001, ISO 13485 and AS9100D.

  • No Minimum Order

    There is no MOQ: a single prototype bore gets the same process discipline and inspection as a production batch.

  • Engineer-Led Review

    Our engineering team, led by 14+ years of hands-on production experience, reviews the bore geometry before cutting starts.

  • 3-Day First Articles

    First-article samples are typically ready in 3 days once the bore geometry, material and tolerance are confirmed.

Bores Verified on Real Parts

Every bore is measured on in-house CMM equipment with traceable, documented results, so straightness and concentricity are confirmed on the actual part. We ship to clients across Europe and North America.

Deep Hole Drilling Capabilities

We size the drilling method to your geometry instead of quoting one blanket maximum depth; exact numbers are confirmed at quote review.

  • Methods
  • Tolerances
  • Inspection

  • Gundrilling and BTA Drilling

    Bore diameter, L/D ratio, straightness and finish move together, so the tooling is chosen per part. Coolant runs through the tool to clear chips and control heat.

    • Single-flute gundrill tooling or BTA boring bars
    • Choice driven by bore diameter, length and material
    • Coolant flow and pressure set per material and diameter
    Learn the Process
    Parameter Specification
    Deep hole threshold L/D over 10:1
    Gundrilling Single-flute tooling
    BTA drilling External-coolant boring bars
    Bore diameter Set by tooling selection
    Max L/D ratio Hardness, rigidity, coolant flow

  • Precision Bore Drilling Tolerances

    These are the values we commit to without qualification, on bores and on the precision machining around them.

    • Shaft-to-bore coaxiality held to ±0.005 mm
    • Sub-10 mm micro features down to ±0.003 mm
    • Workpieces up to roughly 1000 mm long
    Get a Quote
    Parameter Specification
    Fit-critical bores ±0.005 mm
    Micro features (sub-10 mm) ±0.003 mm
    General CNC tolerance As tight as ±0.005 mm
    Workpiece length Up to ~1000 mm

  • QC for Straight Accurate Deep Holes

    A bore that drifts halfway through its length is scrap, not rework, so every deep-hole feature is measured on CMM with full traceability.

    • Documented QMS stages from IQC to CAPA
    • Straightness confirmed on the actual part
    • ISO 9001, ISO 13485, AS9100D certified via TUV
    Learn About Quality
    Parameter Specification
    Bore verification In-house CMM, traceable
    Straightness per meter CMM inspection, FAI
    Achievable Ra First article inspection
    QMS stages IQC, IPQC, FAI, OQC, SPC, CAPA
    Certification body TUV

Deep Hole Drilling vs. Other Hole Processes

Choose deep hole drilling once depth passes about 10 times diameter; below that, standard CNC drilling is enough.

Criteria This ProcessDeep Hole Drilling CNC Drilling CNC Turning
Best for Long, straight bores Shallow holes Features around the bore
Depth ratio L/D over 10:1 Up to about 10:1 Not a drilling method
Straightness at depth Held, CMM verified Drifts off-center Supports bore coaxiality
Heat and chips Through-tool coolant Heat builds at depth Not applicable
Tooling Gundrill or BTA bar Standard drills Turning centers

Deep Bores Across Industries

Medical, energy, industrial equipment and tooling programs rely on deep, straight bores machined and inspected under one quality system.

  • Aerospace

  • Medical

  • Automotive

  • Robotics

  • Semiconductor

  • Electronic

  • Telecom

  • Drone & UAV

  • Energy

  • Oil & Gas

  • Marine

  • Industrial Equipment

  • Construction

  • Agriculture

  • Consumer Products

  • Military & Defense

  • Mining

Typical Deep-Hole Parts and Challenges

Deep, straight bores show up wherever a fluid, shaft or tool must pass cleanly through a long section of metal.

  • Hydraulic Cylinders & Rams

    Bodies up to 1000 mm long keep the through-bore at ±0.005 mm coaxiality over the full length, so the piston never binds.

  • Shafts & Spindles

    Long internal bores in custom shafts and spindles, with shaft-to-bore coaxiality held to ±0.005 mm.

  • Manifolds & Valve Bodies

    Long fluid passages drilled in custom manifolds and valve bodies, then milled around the bores.

  • Mold Cooling Channels

    Deep cooling channels in tooling and mold components, drilled straight along the full length.

  • Medical Instrument Bores

    Small, deep bores for medical CNC machining, under ISO 13485 and with sub-10 mm features to ±0.003 mm.

  • Energy Equipment Housings

    Long bores in energy and industrial equipment housings, often paired with large part CNC machining.

Common Challenges We Handle

  • Bore Drift

    Beyond 10:1, standard drills drift off-center; gundrill or BTA tooling with pilot bushing accuracy keeps the bore straight.

  • Heat and Chip Evacuation

    Through-tool coolant clears chips and controls heat along the full bore, with flow and pressure set per material and diameter.

  • Full-Length Coaxiality

    Fit-critical bores held to ±0.005 mm coaxiality and concentricity, verified on CMM rather than assumed from a catalog spec.

  • Tough Alloys

    Titanium, stainless and Inconel resist sustained cutting pressure; max L/D is confirmed per material at quote review.

Certified Quality for Every Bore

Deep-hole parts run through IQC, IPQC, FAI, OQC, SPC and CAPA, certified through TUV.

  • AS9100D and ISO 9001 certification logo
    AS9100D

    Aerospace Quality Management System

  • ISO 9001 certification logo
    ISO 9001:2015

    Quality Management Standard

  • ISO 13485 certification logo
    ISO 13485

    Medical Devices Quality Management

Metals We Deep-Hole Drill

Long, accurate bores depend on how the material behaves under sustained cutting pressure and heat. These are the alloys we drill.

Metals

Featured Grades

Drilling another alloy? Ask our engineers about your material.

All Metals

How to Order Deep-Hole Parts

  • 1

    Send RFQ

    Share drawings with bore diameter, length, material, tolerance and quantity.

  • 2

    Review & Quote

    Engineer-reviewed quote within 6 hours, with bore method and L/D capacity confirmed.

  • 3

    Confirm Order

    Quote, bore details and delivery schedule confirmed before any cutting starts.

  • 4

    Drilling & Machining

    Gundrilling or BTA drilling, plus milling, turning, EDM or grinding around the bore.

  • 5

    Inspect & Ship

    CMM-verified bores, FAI and traceable records, then packaging and shipment.

Deep Hole Drilling FAQ

Short answers on depth limits, tolerances and drilling methods for long bores.

What is considered deep hole drilling?
A hole is generally considered deep once its depth exceeds about 10 times its diameter (an L/D ratio over 10:1). Beyond that ratio, standard drills lose straightness and surface finish, so specialized techniques like gundrilling or BTA boring are used instead.
How deep can a hole be drilled?
It depends on diameter, material and required tolerance. For fit-critical bores we hold concentricity and coaxiality to ±0.005 mm, verified on CMM, on workpieces up to roughly 1000 mm long; exact depth capacity for your part is confirmed at quote review rather than quoted as a fixed maximum.
How do gundrilling and BTA drilling differ?
They differ mainly in coolant path and tooling: gundrilling uses single-flute tools, while BTA drilling uses external-coolant boring bars. The right choice depends on your bore diameter, length and material, and we confirm it during quote review.

Request a Quote for Deep Hole Drilling Services

Send your bore geometry, material and tolerance; our engineers review it and send feedback before you commit to a vendor.

  • Engineer-reviewed quote within 6 hours
  • No MOQ, from a single prototype bore
  • First articles typically in 3 days
  • Fit-critical bores held to ±0.005 mm
  • Every bore verified on in-house CMM
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