Aero-Lite® pin : Technical Information : AL331 Close Tolerance Head

AL331 Close Tolerance Head

With the introduction of the AL331 close tolerance head AERO LITE™® performance and appearance of skin fasteners. The AL331 is produced with a state of the art manufacturing and head height gaging process that permits installers
To control head flushness while minimizing periphery eyebrow. The AL331 is a dome head fastener designed with the same configuration as the LGPL18 Lockbolt so that use in skin panels is the same maintaining continuity of appearance when installed. The illustration below shows the commonality of the three popular close tolerance head fasteners used by the Boeing Company.
The head protrusion gaging system developed by Boeing and Huck incorporates a precision gage block that locates on the 100° head surface at a gage diameter located on the head angle. The gage block has a concentric through hole sized to fit the fastener shank so that there is no misalignment during gaging. The protrusion is then measured from gage block surface to the top of the head using a digital indicator with a flat stylus that has been preset using a computer calibration method developed by Boeing. The indicator is centrally located to the gage block to insure that the top of the fastener is accurately measured. The test result are recorded, plotted and maintained during manufacturing with Huck’s statistical process control system. The control dimensions for this process are a shown below.

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