In the aircraft industry it occasionally becomes necessary to cold work a fastener hole when the fastener is replaced, in order to avoid premature fatigue. For example, aircraft wing skin is secured to internal wing beams by means of fasteners. During the useful life of the aircraft, it may be necessary to replace some of the fasteners. In such an event it is sometimes advisable to cold work the hole in order to increase fatigue life of the skin.
When cold working the hole, it is advantageous to merely cold work the hole of the skin and not a continuation of the aligned hole which exists in a corresponding support beam.
In order to cold work a hole, a sleeve is frequently inserted therein and a mandrel is forced through the sleeve so that the outward expansion of the sleeve cold works the hole in which the sleeve rests. However, with aircraft skin the exact thickness varies so that a standard length sleeve may not be used.
Up to now it has been a laborious process to measure the depth of the aircraft skin at a particular hole to be cold worked and then adjust the cold working tool to cold work only the hole within the aircraft skin and not the extended hole within the beam. Prior art attempts have fallen short in this respect and have resulted in either incompletely cold worked skin holes or overextending cold working, which adversely affects the structural integrity of fastener holes within the beams.