ISO 9001:2015 Certified Manufacturing
Pilot Hole Design for ecosyn® plast
Engineered Boss Specifications for High-Performance Thermoplastic Assemblies
99.9%
Accuracy Rate
24/7
Global Ops
200+
Containers/Yr
Calculators & Converters
Optimizing Fastener Integrity in Plastics
Fastening into thermoplastics requires a specific approach to handle material flow and prevent boss bursting. The ecosyn®-plast thread geometry features a unique 30° flank angle designed to reduce radial stress during the thread-forming process. To achieve the maximum strip-to-drive torque ratio, your pilot hole diameter must be precisely matched to the specific resin type and boss geometry.
Incorrect pilot hole sizing leads to immediate assembly failure. A hole that is too narrow creates excessive hoop stress, causing the boss to crack. Conversely, a hole that is too large reduces thread engagement, leading to stripped joints and poor pull-out resistance. Our calculations help you find the “sweet spot” for reliable, repeatable plastic assembly.
The Boss Geometry Rule
For most thermoplastics, a Boss OD to Hole ID ratio of 2.0 to 2.5 is recommended to ensure the assembly can withstand the expansion forces of thread forming.
Interactive ecosyn®-plast Calculator
Input your screw diameter and material class to determine the ideal pilot hole size and boss dimensions. These specifications are optimized for ecosyn®-plast thread profiles in commercial resins.
ecosyn®-plast Pilot Hole Calculator
Calculate optimal pilot hole diameters for thread-forming screws in various plastics.
Recommended Pilot Hole (d_h)
Millimeters
PE / PP Hole
--
ABS / PA Hole
--
PC / PBT Hole
--
Boss Ratio (D/d)
~2.0
Pilot Hole (Scientific - Meters)
0.00e+0
*Recommendations based on Bossard ecosyn®-plast technical manual.
Hole diameter $d_h \approx 0.8 \times d$. Specific material tests are recommended for critical assemblies.
Joint Performance Factors
| Design Metric | Engineering Impact | Application Goal |
|---|---|---|
| Drive Torque | The force required to form the thread in the plastic boss. | Ensures efficient assembly. |
| Strip Torque | The threshold where the formed plastic thread fails. | Maximizes safety margins. |
| Radial Stress | Outward pressure exerted on the boss walls during installation. | Prevents boss cracking. |
| Engagement Depth | The total amount of material being displaced by the fastener. | Increases pull-out strength. |
Developing a New Plastic Component?
Our engineering team can perform application testing to determine the exact torque specs and hole designs for your specific thermoplastic resin and assembly requirements.