Body Art News

Internally vs Externally Threaded Posts

Chief Engineer

Patrick Poli

Journal Date

2026-07-28

Last Reviewed

2026-10-14

July 2026 · Body Art News · Poli International

There is a well-worn article on this site about internal versus external threading, and the internet is full of others. They all reach the same verdict, and the verdict is right: a screw thread should never be dragged through a healing wound.

What almost nobody writes is what happens after you accept that. You are left with more than one option, and they are not variations on a theme. They hold together by different physics.

This article compares the two you will meet most often in a metal studio: internally threaded and threadless. There is a third, push-fit, which holds by a tapered interference fit rather than by a thread or a bent pin, and which is covered separately. Be careful with the names: much of the industry, including NeoMetal, uses "push-fit" and "press-fit" as loose synonyms for threadless, even though the retention mechanisms are not the same.

» The professional standard permits both. The Association of Professional Piercers describes internally threaded jewellery as having a smooth post with "the threads on the removable end(s)", and threadless as jewellery that "uses a pin coupling on the ornamental end, and there are no screw threads at all" [1].

» Threadless is not new and not generic. It was invented by NeoMetal in 1997, and the company makes it in implant certified titanium to ASTM F-136 [2].

» Threadless retention is set by hand. The pin is inserted about one third of the way into the shaft and bent between 10 and 20 degrees; bend it further for a tighter fit [3].

» Internal threading is a machining problem. Anatometal describes it as requiring "precise machining to ensure a threaded hole is placed within the barbell end without compromising its durability, regardless of the gauge" [4].

The distinction that actually matters

An internally threaded connection is a fixed mechanical fit. The thread was cut at the factory, to one pitch, and it is either engaged or it is not. Nothing about it changes between the day it was machined and the day you take it out.

A threadless connection is a tension fit, and the tension is a variable somebody chooses. NeoMetal's own instructions are explicit that the bend angle is the retention setting: insert the pin roughly a third of the way, bend it 10 to 20 degrees, and bend it further if you want it tighter [3].

Read those two sentences next to each other and the trade-off stops being a matter of taste. One system arrives finished. The other arrives adjustable, and someone has to adjust it.

Infographic: Internally Threaded vs Threadless: Attachment Systems Compared

What each one is good at

Threadless cannot be cross-threaded or stripped

There is no thread, so the entire category of thread failure disappears. You cannot cross-thread a pin. You cannot strip a socket by over-tightening it. For a piece that gets opened and closed often, that matters more than it sounds, because a stripped internal thread does not announce itself before the end goes missing.

Threadless retention is tunable to the piercing

Because the bend sets the tension, the same components can be set loose enough to change easily or firm enough to survive a jumper being pulled over your head. That is a real advantage on anatomy where the two requirements pull in opposite directions.

It also cuts the other way. A pin bent too little can back out. NeoMetal's guidance for curved and circular pieces is noticeably more involved than for a straight post, calling for a reverse bend against the curve, or an S-shaped bend, with an explicit warning to "avoid over bending" on the smaller circular barbells [3]. This is a skill, not a click.

Internal threading is unambiguous once it is home

A thread that is done up is done up. There is no judgement call about whether the retention is sufficient, no setting that can drift, and nobody has to have understood a bending diagram. For a piece you intend to leave alone for months, that is a genuine virtue.

The cost is in the manufacturing, and it is not trivial. Cutting a threaded hole into a component while leaving enough wall thickness for it to survive is the hard part of the job, and Anatometal names durability as the constraint [4]. This is why quality separates so visibly at small gauges, and why cheap jewellery so often puts the thread on the outside instead: external threading is simply easier to make.

The compatibility trap

This is the part that costs people ends, and it applies to both systems.

Threaded body jewellery has no single industry-wide pitch. Pieces from one manufacturer may not fit another's, even at the same gauge. Threadless has its own version of the same problem: "universal" is a claim that holds within a curated range of components, not across the entire market.

The practical rule is the same either way. Keep a piece within the system it came from, and treat a replacement end from a different maker as something to be tried before it is relied on, not assumed.

Which one should you actually be wearing

For an initial piercing, either meets the standard, so the deciding factors are the ones nobody puts in a comparison table.

Choose threadless if the jewellery will be changed often, if you like the idea of retention that can be tuned, and if your piercer is fitting it. Choose internally threaded if the piece is going in to stay, if it will live under clothing or a helmet, or if you would rather have a connection that does not depend on anyone's judgement about a bend angle.

What should not decide it is price. Both systems, made properly, are made from the same implant certified titanium [1] [2], and a cheap example of either is a worse choice than a good example of the other.

FAQ: the questions that follow

Is threadless weaker than threaded?

No, but it fails differently. A thread holds by mechanical engagement; a threadless pin holds by tension, and that tension is a setting: about one third of the pin inserted, bent 10 to 20 degrees, more bend for a tighter fit [3]. A correctly set pin is secure. An under-bent one is a failure mode threaded jewellery simply does not have.

Can I use another brand's end on my post?

Treat it as something to test, never something to assume. Threaded body jewellery has no single industry-wide pitch, and threadless "universal" fit describes a curated range of components rather than the whole market. Losing an end in a sink usually costs more than buying the matching one.

Which is easier to change myself?

Threadless, in principle, because there is nothing to cross-thread. In practice it depends on the piercing. A straight labret post is straightforward, while curved and circular pieces need a reverse or S-shaped bend, with an explicit warning against over-bending on the smaller circular sizes [3].

Is externally threaded jewellery ever acceptable?

Not for the surface that passes through you. The standard exists because an externally threaded post has "the screw pattern cut into the post, and this comparatively rough surface may be passed through the tissue to insert and remove the jewelry" [1]. That is precisely what both systems on this page were designed to avoid.

Patrick's note

I have spent a lot of years on the manufacturing side of this, and the thing I would want a reader to take away is that these are not two styles. They are two different engineering answers to the same problem, and each one moves the difficulty somewhere else.

Internal threading moves it into the factory. Getting a clean, durable thread into a small component is a machining problem, and it is solved once, by the manufacturer, for every piece that leaves the building.

Threadless moves it to the counter. The parts are simpler, but the retention is not finished until a person sets it, which is why NeoMetal publishes a bending guide at all. That is not a flaw. It is a design that trades factory precision for fitted adjustability, and it works extremely well when the person doing the fitting knows what they are doing.

That is the honest answer to a question the industry mostly skips: the better system is the one whose failure mode you are best placed to avoid.

6. Internally Threaded vs Threadless vs Externally Threaded: How They Actually Differ

Most of the searches that land on this page ask the same thing in slightly different words: what is the difference between internally threaded and externally threaded jewellery, and how does threadless fit into that? The answer is mechanical, not marketing.

Externally threaded jewellery carries the male thread on the post or pin. That thread passes through the fistula every time the piece is inserted or removed, so the exposed metal edges drag across healing tissue. Internally threaded jewellery reverses this: the thread is cut inside the post, and the pin or ball carries the male portion. The surface that contacts the piercing channel is smooth. Threadless jewellery removes the thread altogether. A pin on the attachment bends slightly and seats into a hollow post under tension; there is no screw action and no thread to strip.

So the honest comparison is three-way, not two-way. Externally threaded is the older, cheaper standard and the one I would not put in a fresh piercing. Internally threaded and threadless both meet the professional standard, which is why this page exists. The choice between them comes down to fit and handling: internally threaded gives you a positive mechanical lock and predictable torque, while threadless gives you adjustable tension, faster changes and no thread to cross-thread.

I have been machining and moulding body jewellery for twenty-five years, and I will tell you plainly: the arguments about internally threaded versus threadless are mostly arguments about preferences dressed up as safety claims. Neither design is inherently unsafe when it is made to tolerance. What is unsafe is a poorly machined thread, a counterfeit copy with unknown alloy, or an externally threaded post forced through a fresh piercing because that is what the shop had in stock.

That is why the practical question is not which system wins on paper, but which system your piercer can fit correctly and which matches the piercing. For a fresh lip, eyebrow or cartilage piercing, the priority is a smooth contact surface and a secure fit, and both internally threaded and threadless deliver that when the jewellery is genuine. If you want the material side of that equation, read about BioFlex® body jewellery, PP-R, medical grade, and made for exactly these placements.

If you are still deciding which system to stock or wear, start with the body jewellery material and threading guide and match the design to the piercing rather than to the forum argument.

Mind map · Internally vs Externally Threaded Posts

Internally Threaded or Threadless
- Professional Standards
  The professional standard permits both internally threaded and threadless jewelry for initial piercings.
  - Internally Threaded Design
    - Threads on Removable Ends
    - Smooth Post
  - Threadless Design
    - Pin Coupling System
    - No Screw Threads
- Threadless Tension Fit
  A threadless connection holds together by tension set by bending a pin ten to twenty degrees.
  - Tuning Retention
    - Adjustable Outward Pressure
    - Avoid Over Bending
  - Bending Pin Setup
    - Insert Pin One Third
    - Bend Ten to Twenty Degrees
- Machined Thread Durability
  Internal threading requires precise machining of a threaded hole inside the end without compromising durability.
  - Fixed Mechanical Fit
  - Precise Machining Durability
- Implant Grade Titanium Origins
  NeoMetal invented threadless body jewelry in 1997 using implant certified titanium compliant with standard ASTM F-136.
  - NeoMetal 1997 Patent
  - ASTM F-136 Material

StructureProcessMaterialHazard

4 branches, 0 sources. Each branch cites the article it came from; the labels beneath it are names, not claims.

Body Jewelry Quiz

1. How do true push-fit jewelry connections differ mechanically from threadless pin-coupling connections?
- ✓ Push-fit relies on a tapered interference fit, whereas threadless relies on a bent pin mechanism. — True push-fit components compress together via tapered angles, while threadless systems gain holding force through the spring tension of a manually angled pin.
- • Push-fit uses factory-cut screw threads, whereas threadless relies on friction from an unbent straight post. — Neither push-fit nor threadless systems utilize cut screw threads, and threadless pins require a distinct manual bend to create tension.
- • Push-fit retention is adjusted by hand bending, whereas threadless tension is set permanently during factory machining. — Adjustable manual bending is a defining feature of threadless pin couplings, whereas push-fit retention relies on fixed tapered geometries.
- • Push-fit components hold using an internal ball-bearing detent, whereas threadless relies on external threading. — The source defines push-fit strictly by tapered interference fit and notes threadless explicitly avoids any screw threads.
2. What is the standard procedure for setting the retention tension on a straight threadless post?
- • Insert the pin completely into the shaft and twist it 180 degrees to lock the tension. — Threadless pins do not lock through rotational twisting, as they lack screw threads or twisting locking channels.
- ✓ Insert the pin roughly one third into the shaft and apply a 10 to 20 degree bend. — Partial insertion followed by a slight bend establishes the precise spring tension needed to hold the end inside the post.
- • Bend the entire length of the pin at a 45-degree angle before introducing it into the shaft. — Bending the entire pin at such a steep angle before insertion leads to severe over-bending and prevents smooth entry into the post.
- • Heat the pin to expand the metal prior to press-fitting it fully into the receiving shaft. — Threadless setting is a mechanical hand-bending technique and does not involve thermal expansion or heat treatment.
3. According to the source, who invented threadless body jewelry and in what year was it introduced?
- • Anatometal in 1997 — Anatometal is cited in the text regarding internal thread machining constraints rather than the invention of threadless jewelry.
- ✓ NeoMetal in 1997 — NeoMetal created the threadless design in 1997, utilizing implant certified titanium to ASTM F-136 standards.
- • The Association of Professional Piercers in 2026 — The Association of Professional Piercers provides definitions and standards descriptions, but does not manufacture or invent jewelry systems.
- • Poli International in 2010 — Poli International published the source article in July 2026 rather than inventing the threadless coupling system.
4. What primary engineering limitation makes quality internally threaded jewelry difficult to produce at thin gauges?
- ✓ Maintaining sufficient wall thickness and structural durability around the machined internal socket. — Removing interior metal to tap threads in small-gauge ends risks weakening the surrounding metal wall beyond functional durability limits.
- • Preventing the pin from spring-back unbending after factory machining. — Pin unbending applies to tension-fit threadless pins rather than internally tapped mechanical screw threads.
- • Forming an exterior screw pattern that will not strip upon initial tissue pass-through. — Internally threaded posts feature a smooth exterior surface, as the threads reside inside the socket rather than on the post exterior.
- • Matching the single universal thread pitch mandated across all body jewelry brands. — The source explicitly states that no universal industry-wide thread pitch exists across different manufacturers.
5. What key advantage does threadless jewelry offer over internally threaded options during frequent jewelry changes?
- ✓ It completely eliminates the risk of cross-threading or stripping tiny internal threads. — Without helical screw threads, threadless components cannot suffer from cross-threaded misalignment or thread shear.
- • It guarantees cross-compatibility across every body jewelry brand on the market. — Threadless universal fits are limited to curated component ranges rather than spanning the entire global market.
- • It features an absolute mechanical lock that cannot fail even if bent incorrectly. — An improperly bent or under-bent threadless pin can back out, making correct tension setting vital.
- • It removes all reliance on piercer skill or judgment during initial installation. — Threadless retention relies directly on the fitter's skill to properly angle and set the pin tension.
6. When adjusting threadless ends for curved or circular barbells, what specific bending technique is recommended?
- ✓ A reverse bend against the curve or an S-shaped bend, avoiding over-bending on smaller sizes. — Curved and circular posts require specialized pin shaping to maintain contact points along the curved channel without over-stressing small circular pieces.
- • A single straight 45-degree bend directed toward the center of the barbell curve. — A severe single bend will cause binding or over-bending issues, especially on smaller circular barbells.
- • Filing down the pin length until it sits flat against the internal socket wall. — Altering the length or integrity of the pin by filing destroys the tension geometry needed for retention.
- • Threading the pin using a hand tap to align with the curvature of the post. — Threadless pins are smooth bent wires and are never tapped with threads.
7. Why is combining threaded components from two different manufacturers risky, even if both are the same gauge?
- ✓ Threaded body jewelry lacks a single industry-wide thread pitch. — Different factories cut threads at varying thread pitches, meaning matching gauges may not thread together smoothly or securely.
- • Mixing brands voids the ASTM F-136 titanium certification of both pieces. — Material certification applies to the metal alloy quality itself, not to cross-brand component pairings.
- • Internal threads automatically strip when brought into contact with foreign titanium. — Mechanical thread stripping results from force or pitch mismatch, not from contact between identical metals from different brands.
- • Threaded posts rely on custom-bent pins that deform when paired with foreign ends. — Bent pins are used exclusively in threadless systems, not in threaded body jewelry.
8. Which failure mode is unique to threadless jewelry and does not occur with internally threaded connections?
- ✓ An under-bent pin causing the end to back out due to insufficient tension. — Because threadless retention depends on variable manual spring tension, setting too slight a bend allows the decorative top to slip out.
- • Cross-threading the post during initial end attachment. — Cross-threading is a defect unique to threaded connections and cannot happen on smooth threadless pins.
- • Stripping the internal socket threads from over-tightening. — Stripped sockets occur exclusively when threaded components are forced past their mechanical torque limits.
- • Rough external thread ridges causing tissue damage during insertion. — Rough thread ridges dragging through tissue occur only with externally threaded posts.
9. Why is externally threaded jewelry considered unsuitable for insertion through healing piercing tissue?
- ✓ The exposed screw pattern cut onto the post creates a rough surface that damages tissue during passage. — Passing sharp external thread ridges through an open wound tears delicate healing tissue.
- • The pin coupling mechanism degrades rapidly when exposed to biological fluids. — External threading utilizes cut screw threads on the post rather than a pin coupling mechanism.
- • External threads cannot be manufactured from implant certified titanium. — External threads can be cut into implant-grade metals, but the geometry remains damaging to tissue regardless of alloy.
- • It relies on variable spring tension that inevitably loosens under garment pressure. — Spring tension retention belongs to threadless systems, whereas external threading uses fixed mechanical screw threads.
10. In the author's summary, how do internal threading and threadless systems relocate engineering complexity differently?
- ✓ Internal threading solves precision in the factory, while threadless places retention adjustment at the counter. — Threaded pieces require factory machining to permanently set fit, whereas threadless parts trade factory precision for manual adjustment by the piercer at the counter.
- • Internal threading leaves retention tuning to the piercer, while threadless relies entirely on factory precision. — Internal threading is fixed at the factory, whereas threadless requires the piercer to set retention by bending the pin.
- • Internal threading moves difficulty to the client during daily wear, while threadless requires factory heat treatment. — Neither system requires daily client calibration or post-factory heat treatment to function.
- • Internal threading relies on variable tension fits, while threadless depends on standardized cross-brand pitches. — Internal threading relies on fixed mechanical pitches, while threadless relies on variable tension fits without screw threads.

Extended Reference Table

8 of 8 rows

Extended reference table generated from the article and its verified research sources. Bracketed numbers jump to the matching entry in the Technical References below.

Safety	Item, Material, or Practice	Coupling Type	Usage Recommendations	Biocompatibility Standards & Compliance	Safety & Healing Impacts	Source
✅	Implant-Grade Titanium	-	Recommended for initial and fresh piercings; ideal for sensitive skin and those with nickel sensitivities.	ASTM F-136, ASTM F-1295, or ISO 5832-3	Biocompatible, nickel-free, and inert; supports faster recovery and reduces risk of allergic reactions; can be anodized for color.	[1], [5]
✅	Internally Threaded Jewelry	Internally threaded (screw-in)	Recommended for initial/fresh piercings; best for high-movement areas (tongue, lip, genitals) or large/heavy decorative clusters.	ISO 5832-1 (Inferred) or ASTM F-136	Threads are tucked inside the bar, leaving the post smooth to prevent tissue damage, micro-trauma, and scraping during insertion.	[1], [5]
✅	Threadless (Press-Fit) Jewelry	Threadless (tension-fit)	Recommended for initial/fresh or healed piercings; ideal for frequent swapping of decorative ends and small gemstones.	ASTM F136	Entirely smooth post reduces irritation and bacteria surface area; eliminates risk of cross-threading; requires manual pin bending (10-20 degrees) for security.	[1], [5]
✅	Surgical Stainless Steel	-	Recommended for healed piercings; check for nickel sensitivity. May be used for initial piercings if compliant with specific grades.	ASTM F-138, ISO 5832-1, ISO 10993-(6, 10, or 11), or EEC Nickel Directive	Economical and durable; non-porous finish. May cause irritation in individuals with high metal sensitivities due to nickel content.
✅	14Kt - 18k Gold Jewelry	Threadless or Threaded	Recommended for initial piercings (14k/18k) or healed piercings; must be solid alloy and nickel/cadmium-free.	ISO 5832-1 (General surgical standard)	Biocompatible solid alloys avoid reactions; higher karat gold (above 18k) is soft and may harbor bacteria in surface scratches.
⚠️	Externally Threaded Jewelry	Externally threaded	Avoid entirely for initial or fresh piercings; replace immediately if worn in healing wounds.	-	Exposed threads act like a serrated blade, causing micro-tears and trauma; threads harbor bacteria and "crusties."	[1], [5]
✅	Mirror Polish / Surface Finish	-	Essential standard for all professional-grade jewelry passing through the skin.	Professional standards	Eliminates microscopic ridges and burrs to prevent bacteria trapping, tissue irritation, and plaque/biofilm buildup.	[5]
✅	Hinged Hoops / Clickers	Hinged mechanism	Recommended for healed piercings; popular for septum, daith, helix, and conch placements.	-	Easy to secure and insert without tools; eliminates thread-related trauma but requires a seamless finish to avoid irritation.	[1], [5]

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Technical_References_Archive

[1]Source: Jewelry for Initial Piercings, Association of Professional Piercers
[2]Source: Guide to Threadless Jewelry, NeoMetal
[3]Source: Threadless Pin Bending Guide, NeoMetal
[4]Source: Understanding Internally Threaded Jewelry, Anatometal
[5]Picking your Piercer: safepiercing.org/picking-your-piercer

About the Author

Patrick Poli

Chief Engineer, Poli International · Creator of BioFlex® body jewelry

Patrick has spent 25+ years manufacturing body jewellery and studio equipment, and is the creator of BioFlex® body jewelry. He created the push-fit system so jewellery separates on impact instead of tearing the piercing. He also ran 10 to 25 minute consultations before piercing, and treats aftercare as a standing invitation rather than a leaflet.

More about Patrick →

Last reviewed: 2026-10-14 · Published: 2026-07-28

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