Molded threads
- No extra component or assembly step
- Internal threads may need unscrewing or collapsing cores
- Wear quickly when a fastener is removed often
Decision guide
Molded Threads vs Threaded Inserts: Strength, Wear, and Tooling
Molded threads form the thread in resin. Threaded inserts add a metal thread. Service cycles and clamp load usually decide.
Threaded joints
Plastic threads or a metal insert
The fastener joint decides serviceability and tool complexity.
Molded threads are formed in resin, either internal threads on an unscrewing or collapsible core or external threads across the parting line. Threaded inserts add a metal thread by insert molding or post mold installation.
Repeated assembly and clamp load usually decide. DFM review flags threads that would need complex core actions.
Side by side
How the joint behaves
Resin threads wear. Metal threads add a part.
Threaded inserts
- Metal thread handles repeated assembly and higher torque
- Adds an insert part and a loading or installation step
- Keeps the core simpler when the thread is internal
Routing table
Signals for each option
Qualitative only.
| Factor | Molded threads tend to fit | Threaded inserts tend to fit |
|---|---|---|
| Service life | Few assembly cycles | Frequent service or field repair |
| Load | Light clamp load | Higher torque or vibration |
| Tool | External threads or thread cores | Boss or insert pocket |
| Parts count | Single molded part | Molded part plus insert |
Quote inputs
Send this with your CAD
These decide which thread DFM review recommends.
Thread callout and whether it is internal or external
How many times the fastener will be removed in service
Torque or clamp load at the joint
Whether a self-tapping screw straight into the plastic is acceptable
Continue exploring
Related comparisons
Decision guides and the pages that go deeper.
Compare hub
All comparison guides.
Compare hubUltrasonic welding vs adhesive bonding
Joining molded halves for strength and seal.
Ultrasonic welding vs adhesive bondingPainting vs molded in color
Color from the resin or from a coating.
Painting vs molded in colorMolded in threads
DFM rules for threads formed in resin.
Molded in threadsPost mold inserts
Installing threaded inserts after molding.
Post mold insertsFAQ
Common questions
Are self-tapping screws an option?
Often, for joints that are rarely opened. The boss design matters more than the screw. DFM review checks the boss for cracking risk.
Next step
Quote the thread the way it will be serviced
Upload CAD with the fastener callout. NetProto manufacturing is ISO 9001 certified.