Tapping & Threading

Internal threads.
Any size, any material.
Tap or thread mill.

Complete internal threading capability: production tapping for standard holes, thread milling for tight tolerances and hard materials, heli-coil installation for high-cycle applications. Any thread standard (UNC, UNF, metric, pipe, BSP).

Tapping Quote Thread standards guide

Tap + thread mill Any standard Class 2B / 6H typical Heli-coil capable

01 · What it is

How Tapping works.

Internal threading (creating threads inside a hole) is accomplished through three primary processes, each suited to different applications:

Tapping: A fluted cutting tool (tap) is rotated into a pre-drilled hole, cutting the thread as it advances. Fast, standard, adequate for most applications. Limited tolerance (Class 2B/6H typical), doesn't work well in hardened materials, can break in blind holes. Standard for production volumes in soft to medium materials.

Thread milling: A small single-point or multi-point thread mill tool spirals through the hole while the CNC machine moves in a helical path. Superior tolerance control, works in hardened materials, handles blind holes well, tool is easily replaced if broken. More expensive than tapping but better for precision.

Heli-coil installation: Tapped hole oversized for insert, then a helical wire coil inserted to provide strong internal threads. Used for: soft materials (aluminum, plastic) where tapped threads would strip, high-cycle applications where threads must survive repeated fastener removal, repair of damaged existing threads.

02 · Specifications

Capability specs.

M2–M64

Metric range

Standard metric tapping range. Specialty sizes outside this through thread milling

#0–2"

Inch range

Standard UNC/UNF range. Tap wrenches handle up to 2" diameter

Class 2B / 6H

Standard tolerance

Default thread class. Class 3B / 4H precision available

Blind / through

Hole types

Blind tapping requires special taps; through-hole is easier and cheaper

Production-fast

Tapping cycle

Seconds per tap on CNC — minimal cycle time impact on production

Hardened OK

Thread mill advantage

Thread milling works in hardened materials where tapping fails

Heli-coil

For strength

Thread insert installation for high-strength threads in soft materials

Any material

Compatibility

Steel, stainless, aluminum, plastics, titanium, brass — all tappable

03 · Applications

Where Tapping excels.

Production fasteners

High-volume CNC production with tapped holes — fast integrated cycle

Aluminum housings

M3, M4, M5 tapped holes in aluminum enclosures and housings

Steel structural

Tapped holes in steel brackets, fixtures, industrial hardware

Hardened steel (thread mill)

Thread milling in tool steel, hardened alloys where tapping fails

Blind holes (thread mill)

Deep blind holes — thread mill avoids tap breakage risk

Pipe threads

NPT, BSPT, BSPP pipe thread tapping for fluid connections

High-cycle threads (heli-coil)

Panels with repeated fastener installation — heli-coil prevents wear

Aluminum strength-critical

Structural aluminum threads using heli-coils for strength

Damaged thread repair

Heli-coil repair of stripped existing threads

04 · When not to use it

Not suitable for:

Every process has its limits. Being honest about where Tapping isn\'t the right answer saves time and money.

Very large threads (>2") — specialty equipment required
Non-cylindrical hole shapes — tapping requires round pre-drilled hole
Materials hard enough that thread mill breaks quickly — wire EDM may be needed
Situations requiring thread tolerance tighter than Class 3B — grinding or precision thread milling
Through-holes where exit burrs are critical — may need deburring operation after tapping

FAQ

Tapping questions.

Tapping advantages: much faster (seconds per hole), cheaper tool, standard sizes readily available. Thread milling advantages: better tolerance control, works in hardened materials, single tool handles multiple sizes, no breakage risk in blind holes. For production of standard threads in soft-to-medium materials: tap. For precision threads, hardened materials, or blind holes where tap breakage would ruin the part: thread mill. Thread milling is the "safer" choice; tapping is the "faster" choice.

Three scenarios. (1) Soft materials (aluminum, plastic) under high fastener load — tapped threads may strip; heli-coils distribute load better. (2) High-cycle applications — threads installed/removed repeatedly (panels, service covers); tapped threads wear out. (3) Repair of damaged threads — oversized tap and heli-coil restore functional threads. Cost: $2–5 per installed insert. Plan hole size to accommodate insert diameter.

Classic problem. Tap broken in blind hole is very difficult to remove — often scrapping the part. Mitigations: (1) Use spiral-point taps (push chips forward out of hole). (2) Reduce hole depth to leave clearance below threads. (3) Use thread milling instead — no breakage risk. For critical blind-hole parts, we often specify thread milling automatically to avoid tap breakage incidents.

Standard 75% thread engagement. Example: M6 × 1.0 thread needs 5.0 mm tap drill. Reduced engagement (60%) allows larger drill (5.1 mm) for softer materials, easier tapping. Higher engagement (85%) for strength-critical in hard materials. We specify appropriate drill size based on material and application. See our thread standards guide for complete tap drill chart.

On CNC: tapping integrates into machining cycle. Adds ~2–5 seconds per tapped hole. Cost: essentially negligible on per-part basis for production. For rush or small-batch, tapping can be done on drill press after CNC — slightly more expensive but keeps CNC time focused on primary machining. Thread milling costs slightly more (longer cycle time) but eliminates tap breakage risk and produces better threads.

Standard tapping: no meaningful lead time impact — integrated with CNC production. Specialty threads (non-standard sizes, custom threads): may require custom tooling with 1–2 week lead time. Heli-coil installation: adds 1–2 days to lead time for inserts sourcing and installation. For urgent orders with custom threads, verify feasibility before PO.