Importance

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Abstract

A pull gun (30) is used for pulling a mandrel (32) through an expandable sleeve (126) positioned in a fastener hole (134, 136). The mandrel (32) expands the sleeve (126) as it moves through the sleeve (126), causing the sleeve (126) to prestress the metal which surrounds the hole (134, 136). The pull gun end of the hole is countersunk (138). The pull gun (30) includes an axially split ring (74) having a conical insert (90) which snugly fits within the countersink (138). The sleeve (126) extends through a center opening (80) in the expandable ring (126). Mandrel movement through the portion of the sleeve (126) within said central opening (80) forces the segments (76) of the ring (74) radially outwardly, causing the portions (90) of such ring (74) which are in the countersink (138) to expand and compress the metal which immediately surrounds the countersink (138). A solid film lubricant (127) is provided on the inner surface of the expandable sleeve (126). The coefficient of friction of such lubricant (127) and the contact area (66) of the mandrel (32) with the interior of the sleeve (126) are controlled for the purpose of providing a reaction force which is sufficient to generate enough pressure between the conical insert (90) and the walls of the countersink (138) to adequately compress the metal bounding the countersink (138).

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First Claim