Self-Tapping Thread Inserts for Metal and Plastics
Solid bushings with internal and external threads that cut or form their own thread in a pre-drilled hole — for titanium, aluminum, cast iron and plastics. Type 302/303/307/308/317/318 series, 50+ models, no casting-in required.
A self-tapping insert is a hardened bushing threaded inside and out that installs into a plain pre-drilled hole and cuts its own external thread during installation — no tapping, no casting-in. It provides a high-strength, wear-resistant internal thread in soft or thin materials, and because it goes in after casting or machining, it eliminates the scrap and misalignment risks of cast-in inserts.
What Is a Self-Tapping Insert?
Unlike helical wire thread inserts, which coil into a pre-tapped STI hole, a self-tapping insert is a solid cylindrical bushing. Its outer thread carries cutting slots or forming lobes: as the insert is driven into a drilled hole, it cuts (or forms) its own external thread in the parent material. The inner thread is a precision standard thread ready for your bolt.
Cut a Thread in One Step
The parent hole needs only a plain drilled hole with standard tolerance — no pre-tapping, no reaming. The thread is always precisely positioned relative to the insert body, which is why self-tapping inserts dominate post-machining assembly and field repair.
Cast-In Inserts vs Self-Tapping
Cast-in inserts must be placed in the mold before casting: they can tilt, trap molding sand in the threads, and any misplaced insert scraps the casting. Self-tapping inserts install after casting — higher casting machine output, zero cast-in rejects, and no sand trapped in threads. For die-casting and gravity-casting lines the difference is measured in scrap rate, not just convenience.
Product Range: Series and Types
| Series | Type | Best For | Notes |
|---|---|---|---|
| Type 302 | Slotted, cutting | Widest general use — aluminum, steel, plastics | Two cutting slots with light internal locking |
| Type 303 | Thin-wall | Limited wall thickness | Smaller outer diameter preserves parent wall |
| Type 307 / 308 | Three-hole, cutting | Hard-to-cut materials | 308 is the strengthened, extended version of 307 |
| Type 317 / 318 | Pin, torque-resistant | High-torque service | Locking pin per DIN 1473 resists unscrewing |
| Flanged variants | With flange | Blind-hole sealing, positioning | Flange seats on the surface |
50+ models total — brass and stainless bodies, plain or zinc-plated. M2/M2.5 sizes suit low-strength materials only (driver stud shear limit).
Installation Data (Example: Type 302, M6×1)
| Parameter | Value |
|---|---|
| Insert length | 14 mm |
| External thread | M10×1.5 |
| Drill Ø — aluminum | 9.2–9.3 mm |
| Drill Ø — cast iron | 9.3–9.4 mm |
| Drill Ø — plastic | 9.0–9.2 mm |
| Minimum hole depth | 17 mm |
Drill diameters are listed per parent material because one universal hole either strips soft material or cracks brittle walls — our data sheets give the per-material value for every size. See installation tools for matching drivers and hex tools.
Why Engineers Specify Self-Tapping Inserts
Strength in Thin Walls
A large effective shear area gives high pull-out strength — an M4 self-tapping insert often replaces an M5 tapped thread, keeping more wall thickness in the part.
For Hard-to-Tap Alloys
Titanium and work-hardening steels fight taps. Self-tapping bushings in hardened material hold threads that a tap would gall or tear.
Post-Casting Freedom
Install after machining or even at final assembly — castings stay clean, threads stay true, and scrap stays low.
Serviceable Joints
Standard internal thread accepts bolts repeatedly; the bushing, not the parent hole, takes the wear.
For vibration-heavy heavy-duty joints, compare solid key-locking inserts; for stripped-thread recovery, see thread repair kits.
Self-Tapping Inserts in Titanium Landing-Gear Brackets
Landing-gear attachment brackets in titanium suffered shallow, quickly-worn tapped threads under impact loads — in salt-fog marine environments that also demanded serious corrosion defense. Ankolam supplied titanium self-tapping inserts with a cadmium protective coating (cadmium-free alternatives offered for REACH-sensitive programs): the insert cuts clean threads in the titanium base, the coating withstands marine salt-fog, and the locked thread resists impact loosening and stress-corrosion cracking. Result: long-term corrosion protection in service, zero loosening under impact, used on landing-gear auxiliary attachment points.
Self-Tapping Insert FAQ
Do self-tapping inserts work in plastic?
Yes — plastics are a core application. Drill diameters differ from metals (slightly smaller, see per-material data), and thin-wall Type 303 helps where boss diameter is limited.
Can I install them without pre-tapping the hole?
Yes. A plain drilled hole with standard tolerance is all that’s required — the insert cuts its own external thread during installation with a hand or power tool.
Which series should I choose for high torque?
Type 317/318 pin-type inserts resist unscrewing torques per DIN 1473 — use them where the bushing itself must never back out. For standard duty, Type 302 covers most applications.
What materials are available?
Stainless steel and carbon steel (zinc-plated, yellow-chromated or zinc-nickel) as standard; brass for corrosion-pairing with aluminum and magnesium.
Request a Self-Tapping Insert Quote
Send your parent material, thread size and quantity — we confirm series, drill diameter and tooling within one business day.