Tapped Hole vs Threaded Hole: What's the Real Difference?

Tapped hole vs threaded hole comes down to one relationship: a tapped hole is always a threaded hole, but a threaded hole isn't always tapped. Threaded hole is the umbrella term for any hole with internal threads, no matter how those threads got there. Tapped hole narrows that down to one specific method: a hole threaded using a tap.

That one-sentence answer isn't the whole picture, though. "Threaded hole" on a drawing leaves the manufacturing method open, and that decision has real consequences for cost, tolerance, and which cnc machining factories can even quote the job. The same drawing reaches several factories for quotes on Haizol, since one may default to tapping and another to thread milling, turning what should be a simple side-by-side comparison into two quotes for two different processes.

TL;DR / Key Takeaways

• Every tapped hole is a threaded hole. Not every threaded hole is tapped.
• "Tapped hole" specifies the method (a tap cuts or forms the threads). "Threaded hole" specifies the result, leaving the method to the manufacturer.
• Threads can be created three ways: tapping, thread milling, or thread forming - each with different cost, speed, and tolerance tradeoffs.
• Tapping wins on speed and cost for standard threads in moderate materials. Thread milling wins on flexibility and precision, especially in hardened materials.
• Leaving "threaded hole" on a drawing isn't wrong - it's often the right call - but only if the reader understands what they're delegating to the factory.

 

 

Is a Tapped Hole the Same as a Threaded Hole?

A tapped hole and a threaded hole are related but not identical. Every tapped hole is a threaded hole, since tapping is one of the ways to create internal threads, but a threaded hole can also come from thread milling, thread forming, casting, molding, or a threaded insert - none of which involve a tap at all.

Think of it as a category and a subset. Threaded hole is the category: any hole with internal threads. Tapped hole is one member of that category: a threaded hole made specifically with a tap.

The mix-up happens because tapping is the most common way to thread a hole, especially for prototypes and low-volume runs. When one method dominates a category, people start using the specific term and the general term as if they mean the same thing. They don't, and the difference matters the moment a drawing needs to communicate exactly what a factory should do.

What Is a Threaded Hole?

A threaded hole is any hole with internal spiral grooves cut or formed into its wall, designed to accept a matching externally threaded fastener like a bolt or screw. The hole in a hex nut is a threaded hole. A tapped hole in a bracket is a threaded hole.

A hole with no internal grooves at all - just a smooth bore - is not, no matter how it was made. What makes a hole "threaded" is the finished feature, not the process.

A threaded hole can come from a cutting tap, a forming tap, a thread mill, a single-point lathe tool, an injection-molded core pin, or a pressed-in threaded insert. All six produce a threaded hole, but only the first two are tapping.

This is why "threaded hole" is the safer default term on a drawing when the manufacturing method genuinely doesn't matter to the part's function. It tells the factory what the hole needs to do without dictating how to get there.

What Is a Tapped Hole?

A tapped hole is a threaded hole created specifically by driving a tap - a cutting or forming tool shaped like a screw with sharp edges or ridges - into a pre-drilled pilot hole. The tap either cuts away material to form the spiral thread or displaces it, depending on whether it's a cutting tap or a forming tap.

The process starts with a pilot hole slightly smaller than the fastener's major diameter. The tap threads into that hole, following the pilot hole's own path, and the resulting thread size and pitch are fixed the moment tapping is complete. There's no adjusting the fit afterward the way there is with a thread-milling toolpath.

Tapping is fast to set up and inexpensive per hole on a CNC machining line, which is why it's the default choice on a huge share of drawings, whether the drawing says "tapped" or just "threaded," and leaves tapping as the obvious, cheapest path.

What Is the Difference Between Tapping and Threading?

Tapping is one specific method of threading; threading is the general activity of creating internal or external threads by any method. The three real methods for internal threads are tapping, thread milling, and thread forming, and they trade off speed, flexibility, and precision differently.

Tapping cuts or forms threads with a single-purpose tool sized to one exact thread diameter and pitch. It's the fastest method to set up and the cheapest per hole in moderate materials, but a different tap is needed for every thread size, and once a hole is tapped, the fit is fixed.

1. Thread milling uses a rotating cutter that moves in a helical path inside the hole, essentially combining a mill and a tap into one tool motion. One thread mill can cut a range of sizes and adjust the fit on the fly, which makes it the better choice for hardened materials, large or oversized threads, and jobs where tolerance control matters more than cycle time.
2. Thread milling uses a rotating cutter that moves in a helical path inside the hole, essentially combining a mill and a tap into one tool motion. One thread mill can cut a range of sizes and adjust the fit on the fly, which makes it the better choice for hardened materials, large or oversized threads, and jobs where tolerance control matters more than cycle time.

A quick note on blind holes: if the threaded hole doesn't go all the way through the part, tap selection gets more specific. A taper tap starts easily but can't cut full threads near the bottom of a blind hole; a bottoming tap does the opposite.

Most blind-hole jobs use a taper tap to start the thread and a bottoming tap to finish it. The short version is that "tapped" doesn't automatically mean "threaded all the way to the bottom" on a blind hole.

Tapped Hole vs. Threaded Hole: Full Comparison Table

The table below puts every factor from this article side by side, since no single source covers the full comparison in one place. Use it as a quick reference once you've read the reasoning above.

Factor	Tapped Hole	Threaded Hole (General)
Definition	A threaded hole made specifically with a tap	Any hole with internal threads, regardless of method
Manufacturing methods included	Cutting tap, forming tap	Tapping, thread milling, thread forming, casting/molding, threaded inserts
What it describes	The process used	The finished feature
Flexibility	Low - one tap per thread size and pitch	High - method left to the manufacturer's judgment
Speed and setup cost	Fastest, cheapest for standard threads	Depends entirely on the method chosen
Best production volume	High-volume, standard thread profiles	Varies by chosen method
Best materials	Moderate hardness (aluminum, brass, mild steel)	Any, once the right method is selected
Drawing callout implication	Manufacturer must use a tap, no substitution	Manufacturer chooses the method

Which Materials Work Best With Each Method?

Material hardness and ductility are the biggest factors in which threading method actually works, not just which one is preferred. Soft, machinable metals tolerate all three methods well; hardened and brittle materials narrow the choice fast.

Material	Tapping	Thread Milling	Thread Forming
Aluminum alloys	Excellent	Excellent, high precision	Excellent
Brass	Excellent	Good	Good
Mild steel	Good	Good	Good
Stainless steel (300 series)	Moderate - galling risk	Excellent	Poor
Hardened tool steel	Poor - high tap breakage risk	Excellent	Not suitable
Titanium	Moderate - springback issues	Excellent	Poor - low ductility limits use
Plastics	Good with care	Good	Poor - use inserts instead

Aluminum and brass are the forgiving materials here, all three methods work on Haizol's aluminum CNC machining lines without much debate, so the choice usually turns on volume and cost rather than material limits. Stainless steel is where the methods actually diverge: stainless steel threads are prone to galling, both from a standard tap working the hole and later when a fastener is driven into the finished thread, which is a real reason a factory might quote stainless steel CNC machining with thread milling even though it costs more per hole.

Hardened tool steel and titanium are where tapping becomes a genuine risk rather than just a slower option. A tap under load in hardened steel is far more likely to break than a thread mill doing the same job, and a broken tap stuck in a near-finished part is often unrecoverable without scrapping it.

When Should a Drawing Specify "Tapped Hole" Instead of "Threaded Hole"?

Most drawings only need to specify the thread callout itself, something like M6 x 1 - 6H with a thread depth, and leave the manufacturing method to the factory. That's not vague drawing practice - it's the correct default, because it gives the factory room to pick the fastest, cheapest method that meets the specifications.

Specifying "tapped hole" explicitly makes sense in three situations. First, when the part will see repair or maintenance cycles and the thread needs to be re-cuttable with standard tap-and-drill tooling later. Second, when internal documentation or a customer's own specification requires a particular process for traceability.

Third, when the material and volume genuinely call for tapping's cost advantage and you want that locked in rather than left to a factory's default.

Outside those three cases, "threaded hole" is the better term to put on the drawing. It states the functional requirement - the thread size, class, and depth - and lets the manufacturer match the method to their equipment and the material at hand, which is usually how they'd choose it anyway. For the wider sourcing decisions beyond thread selection, cost, lead time, factory verification, and platform choice, the complete guide to sourcing CNC machining from China covers the whole process.

How Should a Factory's Threading Capability Be Verified?

A factory's threading capability should be verified with documentation, not a services-page claim, because "threading available" tells you nothing about which of the three methods they actually run or how consistently they hold tolerance on it. This is the same scrutiny that applies whenever you're verifying a Chinese CNC factory's production evidence instead of taking a capability list on trust. Ask for evidence tied to the specific material and thread size on your part, not a general capability statement.

A first article inspection report on a threaded feature shows whether the factory measured pitch diameter and thread depth on an actual part, not just a claim that they can. A CMM report against your specific thread callout is stronger evidence than a photo of a tap wall in their shop.

This matters more with hardened materials and tight-tolerance threads, where "we can tap that" and "we can tap that reliably at volume" are two different claims, and only the second one is worth quoting a job against. A factory that's run titanium threading 100 times answers material-specific questions differently than one quoting it for the first time.

Haizol's manufacturing network includes factories running all three threading methods, with custom thread requirements handled through manual RFQ review rather than an automated quote that assumes a default process. That review step is what catches a hardened-steel part that needs thread milling before it gets routed to a shop set up only for standard tapping.

Frequently Asked Questions

Is Tapped the Same as Threaded?

Not quite. Tapped is a subset of threaded - every tapped hole is threaded, but plenty of threaded holes (thread-milled, thread-formed, cast, or fitted with an insert) were never tapped at all.

What Is the Difference Between Tapping and Threading?

Tapping is one specific method of creating internal threads, using a tap tool. Threading is the general term covering any method of creating threads, internal or external, including tapping, thread milling, and thread forming.

Can You Re-Tap a Threaded Hole?

Usually, yes, if the original threads are damaged or need to be cleaned up, and it's common enough to have its own name: chasing. It carries a slightly higher risk of loosening the fit than the original cut, so it's typically done with a purpose-made chasing tap rather than a standard one.

Why Is Threading Called Tapping?

Tapping gets its name from the tap tool itself, a threaded rod with cutting or forming edges that's driven ("tapped") into a pilot hole to cut the internal thread. The term predates modern manufacturing and comes directly from the tool, not the action.

Is a Tapped Hole Always a Threaded Hole?

Yes, without exception. Tapping is one of the methods that produces a threaded hole, so every hole threaded by a tap is, by definition, a threaded hole. The reverse isn't true.

Does a Threaded Hole Always Go All the Way Through the Part?

No. Threaded holes can be blind (stopping short of the far side) or through (breaking out the other side). Blind threaded holes need extra care in tap selection, since a taper tap can't cut full threads all the way to the bottom.

Choosing Between a Tapped Hole and a Threaded Hole Callout

Tapped hole vs threaded hole comes down to a category-and-subset relationship, not two competing terms: every tapped hole is threaded, but threading covers tapping, thread milling, and thread forming as three genuinely different processes with distinct cost and material tradeoffs. Most drawings are better off specifying the thread requirement itself and leaving the method to the factory, reserving "tapped hole" for the cases where the process specifically matters.

The three methods aren't interchangeable once hardness or tolerance gets involved, so which term ends up on the drawing is worth the extra sentence of thought it takes to get right.