Molded-In Insert
Threaded Inserts · insert molding · molded thread insert · captive molded insert
Definition: A molded-in insert is a threaded bushing placed in the mold before plastic injection, so the part comes out with a permanent metal thread encapsulated in plastic.
Anatomy & Schematic
■ Body■ Internal thread
Governing standards: Manufacturer specified (no universal standard)
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| 4-40 | M3 | — | — |
| 8-32 | M4 | — | — |
| 1/4-20 | M6 | — | — |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Brass | brass | — | None |
| Stainless / aluminum | varies | — | None |
Materials
- Brass
- Stainless steel
- Aluminum
Pros & Cons
Pros
- Strongest plastic thread option
- Encapsulated — cannot spin
- No secondary operation
Cons
- Complicates the molding process
- Scrap parts trap the insert
- Mold must be designed for it
Typical Uses
- Injection-molded housings
- Automotive interiors
- Consumer products
- Industrial enclosures
Alternatives & Related
- Ultrasonic Insert — Installed after molding with a welder
- Heat-Set Insert — Post-molding install for prototypes
Where to Buy
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FAQ
What is a molded-in insert?
A threaded bushing placed in the injection mold so molten plastic surrounds it — the finished part has a permanent metal thread.
Molded-in vs ultrasonic insert?
Molded-in inserts are set during molding (strongest, no second op); ultrasonic inserts are installed afterward with a welder (more flexible).