What types of holes and threaded features can be created with CNC drilling services?

Quick Answer

CNC drilling services produce a comprehensive range of hole types: standard through and blind holes, counterbored holes for socket head screws, countersunk holes for flat head fasteners, threaded holes (UNC, UNF, metric from #0 to 2"+), reamed holes for precision fits, and deep holes with specialized gun drilling for depth-to-diameter ratios up to 200:1.

Standard Hole Types

Through holes: Drill completely through the workpiece. Blind holes: Drill to a specified depth without breaking through. Counterbore holes: A larger diameter section at the top for socket head cap screws. Countersink holes: A conical recess for flat head screws. Spotface holes: A shallow flat bottom for washer seating. Center drill holes: Starter holes for lathe work between centers.

Threaded Features

Threads can be created by tapping (cutting threads in a pre-drilled hole) or thread milling (using a thread mill on a CNC machining center). Common thread standards: UNC (Unified Coarse), UNF (Unified Fine), metric coarse and fine (M2 through M30+), NPT (pipe threads), and BSPT. Thread classes: 2B (standard), 3B (precision). Minimum thread depth: typically 1.5x the nominal diameter.

Precision Hole Features

Reamed holes: Drill undersize then ream to final diameter for press-fit bearings and dowel pins. Tolerance: ±0.0002" to ±0.0005". Gun-drilled holes: Deep holes with exceptional straightness for oil passages in hydraulic components, cooling channels in molds, and medical instruments. Depth-to-diameter ratios up to 200:1 are achievable with specialized gun drilling equipment.

Why Choose SOMI Custom Parts

At SOMI Custom Parts, our CNC drilling and tapping capabilities cover the full spectrum from micro-drilling (0.005" diameter) to large-diameter drilling (2"+). We maintain thread gauges for all standard thread sizes and perform in-process thread inspection. Our gun drilling equipment can produce deep, straight holes for hydraulic and mold applications. We also offer combined drilling + tapping in a single CNC cycle for maximum efficiency.

Case Study

A hydraulic manifold manufacturer required 24 precision-drilled and tapped ports on each manifold block, including 8 cross-drilled intersections and 4 NPT pipe thread ports. SOMI programmed the complete drilling cycle on a 4-axis machining center, drilling all holes and tapping all threads in a single setup. The 1,500-piece order was completed with zero thread gauge failures and 100% pass rate on pressure testing.

Industry Data

Drilling and tapping account for approximately 25-35% of all CNC machining operations (Gardner Business Media, 2025). Thread milling has grown 40% over the past 5 years as manufacturers adopt it for its ability to produce threads closer to the bottom of a blind hole and with better thread quality than conventional tapping.

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