Fastener for Engineering Grade Plastics
Good resistance to vibrational loosening
Single lead design reduces assembly stresses
Exceptional performance in engineering grade plastics
Wide spaced, single lead 45° thread design
Tapered lead point
The PLASTITE® family of TRILOBULAR™ screws for fastening in plastic
The following is intended as a guide to choosing threaded fasteners which will provide optimum application and performance characteristics in a wide range of plastics. It contains detailed information on PLASTITE® threadrolling screws.
Because of the variations in the manufacture of individual grades of plastics, particularly in the quantity of filler used, it is imperative that tests be conducted on each proposed application by a competent engineering laboratory.
Reduced hoop stress. The PLASTITE® screw’s TRILOBULAR™ design reduces dangerous hoop stress and the friction of root interference, which can frequently cause the bursting of thin-walled bosses.
Better quality threads. The smooth burnishing action of PLASTITE® thread rolling screws eliminates the dangers inherent in the use of thread-cutting screws. PLASTITE® screws roll form high-quality internal threads with no damage to the molecular structure of the plastic, significantly reducing the danger of material failure.
Fast, cost-effective application. The easy starting, easy driving capabilities of PLASTITE® screws cut assembly time and costs. Exceptional holding power eliminates the need for costly inserts and lock washers.
Fewer torque problems. The unusually high drive-to-strip ratio of PLASTITE® screws permits a wider span of torque settings to be safely used with automatic drivers. Strip-out is virtually eliminated.
REMINC/CONTI’s network of licensees usually provides this testing service without obligation. This provides the design engineer with recommendations in the following areas: type of fasteners, quantity, sizes, design of the fastening site or boss, and hole sizes. Torque values are needed for power tool settings during assembly, including drive, strip, seating, breakaway, and prevailing off torque. A written report on the test results is usually provided.
Resolution of Resultant Forces comparing PLASTITE 45 thread form with standard 60° thread form.
How the TRILOBULAR™ family optimizes fastener performance and lowers in-place costs.
PLASTITE® TRILOBULAR™ thread-rolling screws were developed specifically for use in plastics. They combine a unique TRILOBULAR™ cross-sectional form with deep, wide, spaced threads.
Easier to drive. Three swaging lobes with full relief of the thread form reduce driving effort and operator fatigue.
More holding power. The three-lobed design of PLASTITE® screws takes full advantage of the cold flow characteristics of many plastics by allowing plastic material to recover and fill in between the lobes. This establishes maximum resistance to vibrational loosening. In addition, the screws’ deep, coarsely-spaced threads provide a heavier shear area and deeper thread engagement in the plastic, further enhancing holding capabilities.
PLASTITE® 45 Screws
PLASTITE® 45 screws represent the latest refinement of the cost savings and performance capabilities of TRILOBULAR™ technology for assembling plastic components. The TRILOBULAR™ shape uses the plastic’s natural resiliency and creep characteristics, allowing the plastic to fill in the depressions between the lobes. This helps lock the fastener, providing prevailing torque if fastener removal is attempted. Years of research revealed that exceptional performance could be achieved by combining the TRILOBULAR™ shape with the following attributes:
- Wide thread spacing
- Narrow thread angle
The extra wide thread spacing and more acute thread angle of PLASTITE® 45 screws keep induced stress to a minimum during the thread-forming operation. These attributes also permit a deeper thread without increased drive torque. Also, the extra wide thread spacing allows stress to be dispersed over a greater area in the plastic boss or nut member, and the plastic material remaining between the threads is left strong and intact, thus providing for high assembly loads and stripping resistance. The narrow thread angle reduces stress by displacing less material and creating less bursting pressure (See the above illustration).
Hardened and tempered screws are significantly stronger than plastic, so if the assembly becomes over-torqued, usually the plastic will give way and strip out. Strip-out in the plastic will occur cylindrically, so the more nut member material that remains within the cylinder, the more resistant the plastic will be to strip out. It is, for this reason, the wide thread spacing of a PLASTITE® 45 screw increases the assembly strength at the same time that it reduces stress.
PLASTITE® 45 screws are the perfect balance between application needs and efficient manufacturing for consistent performance.
PLASTITE® 48-2 Screws
PLASTITE® 48-2 screws have a TRILOBULAR™ body like PLASTITE® 45 screws but incorporate a double lead, two-start thread. The steeper helix angle from the double lead permits higher fail torque to be obtained, usually resulting in a higher differential between fail torque and thread forming torque, which allows easier power tool adjustment when assembly stripping is the problem.