Composi-Lok®

Composi-Lok animation

Composi-Lok_IIDesigned for use in composite laminates but equally well suited to metal structure, the Composi-Lok family of fasteners provides superior joint integrity. Composite laminates are capable of sustaining high loads but are subject to delamination when fastened with conventional fasteners. By providing a large blind side upset, hailed by some as the industry benchmark, Composi-Loks distribute bearing loads over a large area overcoming damage to the composite. The characteristic large blind side bearing area or “footprint” allows the fastener to impart very high clamp loads to the structure without damage to the composite. Structural integrity in severe vibration environments is assured by a patented locking feature. Proper installation can be achieved with simple and compact hand or power tools and verified from one side of the structure by measurement of the screw break-off position. Available in four distinct 75 KSI shear strength versions, all Composi-Loks are completely compatible with graphite and are not subject to galvanic corrosion. Composi-Loks are available in 5/32” through 3/8” diameters, including oversizes, and have a .050” operational grip range.           

Composi-Lok II fasteners incorporate Monogram’s drive nut concept further simplifying the installation process by incorporating a disposable hex drive nut. The hex drive nut provides a positive fastener-to-tool engagement and eliminates the tendency for flush style fastener recesses to “cam-out” during installation. Since the drive nut is common to a variety of diameters and all head styles only three nose pieces are required to install the entire Composi-Lok line. Nose pieces never wear out and the disposable magnetic drive nut stays on the discarded pintail after installation permitting easier retrieval and minimizing the chances of small pintails finding their way into F.O.D. critical areas. Composi-Lok IIa and Composi-Lok3 variations also incorporate the drive nut feature.

For automated or robotic assembly Composi-Loks can also be supplied with Monogram’s Double Cylindrical Drive (DCD) system. The DCD system provides a common tool interface regardless of head style, fastener grip, or diameter. And, because the interface and drive mechanism are cylindrical, there are no orientation problems!

All Composi-Loks provide these important advantages:

  • Large blind upset eliminates composite damage
  • Easy, labor saving one-sided installation further simplified by the drive nut concept
  • Controlled clamp up - no gaps and tighter assemblies
  • Completely compatible with graphite – available in titanium or cres materials to resist galvanic corrosion
  • Visual locking feature resists loosening due to vibration
  • Fuel tight sealing capability

Composi-Lok IIa fasteners, with their unique design characteristics, address the inherent thickness variations of composite material stack-ups. These common variations make proper grip measurement practices imperative to assure proper fastener performance and joint integrity. These concerns are minimized by the ability of the Composi-Lok IIa to function properly even when installed .050” beyond its prescribed grip accommodation.
While design considerations should be limited to the optimum performance characteristics of the fastener within its prescribed .050” grip range, the added assurance of joint integrity in limited out of grip conditions is available with Composi-Lok IIa. This extended grip capacity of .025” under minimum grip to .025” over maximum grip (for a total of .100”) with no composite damage and joint performance still in excess of guaranteed minimums makes the Composi-Lok IIa one of the most tolerant blind fasteners for composites on the market.  

Composi-Lok3 is the newest cost saving design in the Composi-Lok series. With one of the most trusted names in aircraft assembly as its foundation, Composi-Lok3 delivers lower installed costs and increased productivity. *Designed to afford a flush to below flush break-off, the Composi-Lok3 requires no secondary shaving, milling or grinding operations to meet aerodynamic flushness requirements. All the performance and reliability of our Composi-Lok is now available with a flush break-off. Without compromise on mechanical properties, high preloads or large blind side head formation, you save on tooling expense as well as the time and cost of shaving while productivity is increased with labor dedicated to other tasks.

*Composi-Lok3, with its controlled break-off, requires alternative means of post-installation inspection.

For tooling information for Composi-Lok II, Composi-Lok IIa and Composi-Lok3 fasteners please refer to the appropriate Installation and Inspection Specification download link under Product Details