Screws & Inserts for Plastic: PT 30° vs. Plastite 45°
1. Why “ordinary” screws struggle in plastic
- Metal threads cut the boss, leaving chips and weakening the wall.
- High drive torque can split thin-wall or 3-D-printed bosses.
- Plastic creeps over time — steel threads relax and loosen.
Plastic-forming fasteners displace material instead of cutting it, creating chip-free threads with low drive torque and superb vibration resistance.
2. Thread-forming / thread-rolling screw families
| Geometry | Flank Angle | Best for | Collections |
|---|---|---|---|
| PT / EJOT-style | 30° | Thin bosses, lowest drive torque | Metric PT screws | Inch PT screws |
| Plastite® / Plas-Fix 45 | 45° trilobular | Higher pull-out, tougher plastics | Same collections – look for “45° Plastite/Plas-Fix” titles |
Rule of thumb: choose PT 30° for the lowest seating torque; choose Plastite 45° for the highest strip-out strength.
3. Heads, drives & materials you can mix-and-match
- Heads: pan, flat (82°), round-washer — trade clearance for bearing surface.
- Drives: Torx® > Pozidriv > Phillips for torque and cam-out resistance.
- Materials/finishes: A2 stainless, zinc + bake + wax, black oxide + wax.
4. When a threaded insert is the better answer
If you need dozens of service cycles or very high clamp loads, switch to heat-staked brass inserts:
- Metric E-Z Press inserts — shop now
- Inch E-Z Press inserts — shop now
- Installation tip — E-Z Sonic heat-stake tip
5. Quick selection cheat-sheet
| Application | Recommended fastener |
|---|---|
| < M2.5 boss / 3-D print | PT 30°, Torx pan, stainless |
| Auto-trim, high pull-out | Plastite 45°, Torx pan, Zn + wax |
| Flush appliance fascia | Plastite 45° flat head, Pozidriv |
| Repeated servicing | E-Z Press insert + machine screw |
| Outdoor IoT enclosure | PT 30°, Torx pan, stainless |
6. Installation pro-tips
- Pilot Ø ≈ 70–75 % of screw major Ø (see charts on collection pages).
- Drive 300-800 RPM; stop at 80 % of strip-out torque.
- Boss OD ≥ 2 × screw major Ø for best load distribution.
- Heat-stake inserts only until a small melt bead forms, then cool under pressure.
Ready to spec your fastener?
Need help with boss geometry or torque targets? Contact the Monster Bolts tech team – we’re happy to assist.