Solving Assembly Problems and Reducing In-Place Fastening Costs

POWERLOK® II™ screws are an all-metal locking fastener that resist extreme temperature variations and vibrational loosening.  Its locking action results from a Dual Angle™ thread design so revolutionary it was granted a patent.  POWERLOK® II™ screws provide locking without using patches, adhesives or other features and the locking action runs the entire length of the screw.  POWERLOK® II™ screws also provide excellent grounding as the metal locking feature ensures metal-to-metal contact as do TAPTITE® PRO™ thread rolling fasteners, which functionally tap their own threads.  This feature makes POWERLOK® fasteners and TAPTITE® fasteners well suited to grounding applications on electric vehicle (EV) and internal combustion engine (ICE) platforms.

POWERLOK® II™ Fastener Advantages

  • No need for patches or adhesives.
  • Locking action is over the entire length of the screw.
  • Locking action is not affected by temperature.
  • No adhesive curing time; instantaneous locking action.
  • No need for under-head locking elements, such as lock washers.
  • Work with all finishes.
  • Easily hand-started.
  • Cross-threading resistant.

POWERLOK® II™ Fastener Geometry - Enhanced Locking Ability

A POWERLOK® II™ screw’s TRILOBULAR® shape and self-locking action make it a unique locking screw.  Made from carbon or alloy steel, hardened and tempered to an optimum strength for toughness and serviceability, POWERLOK® II™ screws achieve enhanced locking action through the combination of a Dual Angle™ thread form and a TRILOBULAR® thread body section.  A significant mechanical advantage of this design is that the locking action is developed at the outermost radius of the torque arm of the screw body, whereas other locking screws develop their effective resistance at lesser radius points on the thread flanks, even down to the thread root surface.  The deeper geometry of the POWERLOK® II™ screw thread, along with a slight increase in the thread’s major diameter over an equivalent size machine screw, adds to the effective stripping resistance of the fastener.  In addition, the centralization of the POWERLOK® II™ screw lobes in the nut member allows the crest on the fastener thread to flex elastically under clamp load, simulating the live action of a spring washer.

Continuous Locking Action

POWERLOK® II™ screws do not have to be seated to lock, as the locking thread feature extends the entire length of the fastener.  They resist vibration at any point along their body length.  Consequently, POWERLOK® II™ screws are excellent for adjusting screw applications.  The locking action is instantaneous and, unlike time-sensitive chemical locking agents, no reaction or curing time is required.

Resistant to Temperature Extremes

POWERLOK® II™ screws do not lose their action or efficiency in high temperature environments.  Non-metallic additives, featured with many locking screw designs, lose much or all of their developed force and/or deteriorate with time under the influence of temperatures 200°F or higher.  A POWERLOK® II™ screw, being an all-metal locking fastener, is completely unaffected by these high operating temperatures.


Subjecting a POWERLOK® II™ screw to increasing clamp load results in continuously increasing thread flank contact, so that unit pressure between the mating surfaces tends to remain constant, an important factor in minimizing galling and abrasion.  Combined with the burnishing action of the TRILOBULAR® crests, a POWERLOK® II™ screw maintains continued locking effectiveness, even after repeated insertions and removals.

Locking Performance

POWERLOK® II™ screws will meet or exceed IFI 124 (inch) or IFI 524 (metric) specifications for prevailing-torque locking screws.  Transverse vibration test data is available upon request.  Actual performance will vary depending upon effective finish lubricity and nut condition.

No Special Taps

POWERLOK® II™ screws save time and money by allowing the use of standard nuts or Class 2B (6H) tapped holes.  POWERLOK® II™ screws are precision made, so the nut’s threaded hole can be made using standard customary tolerances.


POWERLOK® II™ screws are widely used in automotive and other mass-assembly operations and are ideally suited wherever you need reliable vibrational resistance and continued high performance, despite repeated assembly and disassembly, using standard tapped holes.  They can also be used in pre-tapped holes in ductile metals.

Standard Material

POWERLOK® II™ screws are manufactured from low carbon, medium carbon or alloyed steel and then hardened and tempered to the optimum combination of tensile strength and toughness.  Screws can be made in strength levels to suit a wide range of application requirements.  Property Class 10.9 is often preferred.  Finishes can be applied as required.

Anti-Cross Threading Feature

POWERLOK® II™ screws are used in pre-threaded nuts or threaded holes, conditions which typically create the same concern about cross-threading that exists when using standard machine or metric screws.  POWERLOK® II™ screws have been evaluated for starting efficiency, using the same test procedures and equipment utilized to examine the potential for machine and metric screws cross-threading.  In an extensive test comparing M6 x 1 POWERLOK® II™ screws with popular competitive anti-cross threading screws, POWERLOK® II™ screws experienced a zero incidence of cross-threading, while the competitive screws experienced a 11% cross-threading incidence.  These tests were performed using 7 and 9 degree off-axis angles with several different types of standard commercial threaded nuts.  Test data is available upon request.  The standard 4-pitch sharp-crested lead threads that are incorporated in the POWERLOK® II™ screw design, provide excellent anti-cross thread protection.

POWERLOK® II™ Documents