Designed for the Demanding Plastic Applications of Today and Tomorrow
The REMFORM® II™ screw is a round-bodied thread forming fastener with a unique thread form to provide superior performance in today's wide range of plastics. The asymmetrical thread minimizes radial hoop stress to reduce boss bursting. The narrow tip angle also reduces stress in the plastic nut member.
The Unique Radius Flank™ Thread Form
REMFORM® II™ screws employ the Unique Radius Flank™ asymmetrical thread form shown in the drawing to the right. The leading thread flank is most influential in forming the mating thread. The intercepting radius form on the leading flank promotes efficient material displacement and material flow. The pressure flank which opposes the fastener head, is engineered to resist pull-out forces, whether they be applied by a tensile load or induced by torque. The steep pressure flank has a subtle radius designed to increase resistance to pullout and to efficiently develop tension. It also provides excellent material contact resulting in a high resistance to internal threads stripping. In applications where the failure mode is fastener fracture, the high torsional strength of REMFORM® II™ fasteners ensures a high failure torque. This unique thread and its narrow tip angle efficiently displace material and therefore require minimal energy to form an internal thread. The tip also utilizes a radius to better create the internal thread without increasing hoop stress in the plastic.
The REMFORM® II™ Screw's Unique Thread Form
The steep trailing flank on the REMFORM® II™ screw's unique asymmetrical thread form is engineered to resist pullout, whether it be applied by a tensile load or induced by torque. When a threaded fastener is tightened, the trailing flank has to resist being pulled toward the direction of the head. Nearly all the load is between the screw's trailing flank and the adjacent nut thread's flank. The leading thread is most influential in forming the mating thread. The narrow angle intercepting a radius form on the lead flank promotes efficient material displacement and flow.
The REMFORM® II™ Screw's Strength
The REMFORM® II™ screw is strong. With a higher torsional strength than many spaced thread fasteners, REMFORM® II™ is able to utilize this strength along with its superior thread forming ability to allow deep lengths of engagement. These deep lengths of engagement allow REMFORM® II™ to outperform other spaced thread screws since more holding power can typically be obtained by increasing the engagement length rather than increasing the diameter of the screw, which results in relatively small performance gains, at a higher cost.
The deepest engagement a screw can be inserted into is typically the point where the nut threads are formed to a strength level where the screw fails by breaking rather than the hole stripping. With weaker screws these deep engagements are not possible since the thread forming torque for such deep engagements will approach the breaking torque of the screw. Even when engagements are not deep enough to break the screw, REMFORM® II™ screw's high stripping torque and low thread forming torque provide a wide comfortable margin in which the seating torque may be chosen.
Thread Forming Torque
The unique thread form and sharp tipped threads provide low thread forming torque by efficiently moving and displacing material.
High Failure Torque
In applications where screws fail by torsional breaking when subjected to ultimate torque loads, the REMFORM® II™ fastener's high torsional strength assures a high failure torque. In applications where the failure is due to the fastener stripping the nut threads, the steep trailing flank puts most of the resisting force in an axial direction as opposed to a radial direction, to increase the resistance to stripping.
A wide torque range between thread forming and failure torques facilitates assembly by allowing an assembly torque that provides a comfortable margin between the assembly and failure torques. This wide torque range assures that all screws are fully tightened, eliminating the possibility of stripped assemblies.
Reduced Hoop Stress
REMFORM® II™ screw's radiused leading thread flank reduces hoop stress by minimizing radial forces during thread forming and upon the tightening of the fastener. The trailing flank's steep angle transfers most of the resultant forces developed in the tensioning of the fastener along the screw's axis, minimizing the boss bursting radial forces.
The REMFORM® II™ screw was developed with total quality design in mind. Many fasteners are developed with little regard to the manufacturing processes used to produce fasteners and the limits these processes impose upon the fastener design. The result is designs that cannot be made efficiently. This results in fasteners that do not maintain their intended shape along the whole shank, have poorly filled out thread forms, or deviate erratically from the intended design specifications. These deficiencies usually result in erratic performance, hampering attempts at quality assembled joints.