LHP™ Lockbolt

Howmet Fastening Systems’ LHP fastener is a modified version of the HUCKCOMP® fastener, incorporating similar design features. This fastening system has a large bearing area provided by a large pin head and a flanged titanium collar. The collar provides a high clamp load distributed over a wider area, keeping materials safe and undamaged. The large bearing area and high clamp force give the LHP fastener the ability to enhance joint integrity and fatigue performance.

Design features

Our LHP lockbolt fastener is offered in LHPL8SC with 100° MS24694 flush heads, LHPL7SC 100° MS20426 flush heads, LHPL9SC 130° low-profile large bearing flush heads, LHPL9SP low-profile large bearing protruding heads, and LHPL12SP intermediate large bearing protruding heads. All LHP fasteners are 6Al-4V titanium at 95 KSI shear strength.

Collars for the LHP fastener are 3Al-2.5V titanium, which provides an all-titanium fastener installation and is compatible with graphite epoxy type composite materials.

The LHP lockbolt features lock grooves with a tapered root diameter and variable pitch. A larger volume of collar material flows into the locking grooves at the beginning of the installation sequence. This gives the fastener its greatest tensile strength during the most crucial stage – swaging of the collar – so that a high clamp force can be developed without loss of strength during collar swaging/extrusion. As a result, the fastener achieves a high residual clamp and high ultimate tensile. The 60° included angle of the locking groove has a 20° pressure flank angle, which serves as a platform for retaining the high clamp load generated during collar installation.

Cost-effective features

Sloped surface installations:
The LHP fastener can be installed on sloped surfaces up to 5° on the collar side of the material being fastened. With this feature, heavy, costly self-aligning washers and special nuts are not required. Inventory costs as well as structural weight are reduced. Fewer parts translate into greater labor efficiency.

Extended grip range:
The LHP fastener has a usable 3/32 in. grip range, which reduces inventory and installation errors that are common when using conventional 1/16 in. grip range fasteners. The extended grip range makes the LHP fastener more forgiving if the installer needs a fastener just over or under the recommended grip, which often happens when fastening composite materials due to variations in material thickness and use of liquid shim materials.

The labor-intensive job of over-coating each fastener or the use of heavy, costly sealing nuts is eliminated with the LHP fastener. Annular grooves on the pin form a series of separate barriers to prevent fuel seepage. Fay surface sealant flow during installation due to high clamp load ensures reliable fay surface sealing.

Vibration resistance:
Because the LHP fastener uses annular instead of helical grooves, installation is made with a tension/tension action rather than a torque/tension action. Therefore, there is no path for loosening in a vibrating environment.

Low collar-side clearance:
The installed height profile of the LHP fastener is significantly lower than that of a threaded fastener. Its low collar-side profile enables it to fit in tight space areas.

Minimal rework:
Since the LHP fastener is a pull-type installation, there is no surface damage, which often is associated with torque type fasteners.