Designed Primarily for Plastic Applications
The REMFORM® Screw is a thread rolling 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
Both REMFORM® Fasteners 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 lead flank is there to promote efficient material displacement and material flow. The steep trailing, or 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. This unique thread and its narrow tip angle efficiently displace material and therefore require minimal energy to form an internal thread. The steep trailing flank with excellent material contact results in a high resistance to the internal threads stripping. In applications where the failure mode is fastener fracture, the high torsional strength of REMFORM® fasteners ensures a high failure torque.
Reduced Hoop Stress
When a threaded fastener is tightened, nearly all of the axial tightening load, designated F, is opposed by the trailing, or pressure, flank of the screw and the mating thread flank of the internal thread. The narrow 12.5° angle of the pressure flank transfers most of the resultant tightening load in the axial direction, Fa, minimizing boss bursting tendencies created by the radial force, Fr. The axial force, Fa, is over 4.5 times greater than Fr, the radial force.
Optimal Material Flow
The radius thread flank of the REMFORM® screw thread minimizes radial forces during thread forming, resulting in low thread forming torque. The asymmetrical thread form of the REMFORM® fastener produces asymmetrical opposing resultant forces off the thread flanks during thread forming, creating improved material flow. The picture to the left shows the material flow towards the thread root which results in greater material contact along the pressure flank of the fastener, increasing resistance to stripping. The reduced contact along the leading flank reduces friction during thread forming and lowers the thread forming torque.
Low thread forming torque, when coupled with high failure torque, results in a wide, safe assembly torque range.