The Maf Fastening System provides a simple, straight forward solution for fastening materials which are sensitive to high clamping loads. This three piece system, consisting of a fine pitch threaded pin and sleeve and locking collar provides precise controlled clamp-up of materials such as composite sandwich panels, soft core foam panels, metallic sandwich panels or other materials which may be sensitive to high bearing stresses. Because the threaded sleeve is “free running” (void of prevailing torque type locking devices) installation torque values can be precisely adjusted to yield the controlled clamping force required by the joint design specification for the structure. A unique positive mechanical lock, independently installed after the torquing operation, makes the fastener ideal for use in vibration and F.O.D. critical applications. The slight protrusion of the pin after installation may be shaved with conventional shaving tools to provide optimal flushness on aerodynamic surfaces. These features combine to make the Maf ideally suited to the soft core or honeycomb panels used in engine nacelles, fairings, control surfaces etc. The Maf system is available in three configurations; full shank, reduced shank diameter and variable grip. Each functions in a 1/16” grip range, is available with protruding heads, a protruding / flush combination or a double flush (flush sleeve & flush pin) configuration and is manufactured in 11/64” through 21/64” nominal diameters with 1st and 2nd oversize availability. Four different materials; 8740 alloy steel, A-286 cres steel, Inconel-718 and 6AL-4V titanium alloy provide shear strengths of 95KSI and 108 KSI.
Monogram’s adjustable preload Maf Fastening System is comparable to the Alcoa ASP® Fastening System. For more information on compatibility and interchangeability please contact Monogram Aerospace Fasteners.
Typical Installation Sequence
- Step 1: From one side of the material to be fastened insert the pin into the prepared hole then place the threaded sleeve over the pin threading it onto the pin. Using a special driver to engage the slot on the sleeve tighten the sleeve to a predetermined torque based on the desired compression of the joint/material. Exercise care not to over torque the sleeve as this may cause damage to the soft core material.
- Step 2: Remove the sleeve driver and place the locking collar over the pintail positioning it in the conical recess of the sleeve.
- Step 3: Place the installation tool’s nose assembly completely over the pin protrusion so as to contact the lock ring while engaging the pin’s pulling grooves. Activation of the installation tool forces the lock ring into the conical recess of the sleeve as well as the threads on the pin. Helical splines on the pin thread assist in providing a secure anti-rotational mechanical lock.
- Step 4: With the lock now set the installation tool forces build and fracture the pintail at the break groove. The installation load is absorbed entirely by the fastener with no affect to the materials being joined. The remaining pin protrusion may be shaved to meet aerodynamic flushness requirements.