Best Threaded Inserts for Plastic
Plastic cannot hold a screw thread long-term, so you install a brass or steel insert instead. Heat-set inserts are the standard for 3D-printed and injection-molded parts.
What to Look For
- Install method: heat-set (soldering iron) for plastic, or self-tapping press-in for sheet and thin walls.
- Material: brass for most parts; stainless where strength or corrosion matters.
- Thread: match the screw — metric for most 3D prints.
- Knurled or helical OD: grips the melted plastic so the insert cannot spin.
Top Picks
1. Brass heat-set insert assortment (M2 to M6) Best overall
The standard for 3D-printed parts — knurled bodies that melt in cleanly with a soldering iron.
Check price on Amazon →2. Stainless heat-set inserts For strength
Harder-wearing threads for parts that get assembled and disassembled often.
Check price on Amazon →3. Self-tapping press-in inserts No heat needed
Press into a drilled hole in thermoplastics without a soldering iron — faster for production.
Check price on Amazon →What to Avoid
Avoid
- Tapping plastic directly — the thread strips after a few uses.
- The wrong hole size — too small splits the part, too large lets the insert spin.
- Plastic screws in heat-set inserts for high-load joints.
Bottom line: Brass heat-set inserts are the default for plastic and 3D prints; go stainless for repeated use and self-tapping inserts where you cannot apply heat.
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