Fatigue Technology, Inc.

Other

Robert L Champoux

Charles M Copple

The method of fastening a plurality of metal members (82, 84; 232, 230) in which precision holes (86, 88; 236, 234) are drilled through the metals which are to be connected together. The drilled holes in the metal members are cold-expanded to improve the fatigue performance of the metal surrounding the hole and at the same time size the hole. Then a fastener (254) sized to make a desired fit is installed into the hole. The final hole diameters (236A, 234A) after expansion are equal to the starting hole diameters plus the retained expansions, there being spring back shrinkage of the expanded holes to the final hole diameter. The holes are sized by expanding them to at least a critical sizing expansion value which is a value of expansion beyond which the retained expansion value is linearly exceeded and to nearly the same amount as the total expansion before elongation of the hole axis of the metal surrounding the hole. This is a method of cold-expanding a series of holes to size in which the same tools are used, with the result that the holes are varied in the diameter no more than 0.001'.

Method of cold expanding and sizing fastener holes

A pull gun (10) is used for pulling a mandrel (12, 150, 180) through an expandable sleeve (74, 144, 180) positioned in a fastener hole. The mandrel expands the sleeve as it moves therethrough causing the sleeve to put the metal which surrounds the hole in a state of compression. The pull gun has alternative extensions or sleeve retainers having general appearances of collet chucks and they are adapted to be positioned adjacent holes being prestressed. The retainers are of relatively small diameter for operation through a drill fixture and in small spaces on a workpiece.

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Bellevue, WA, United States of America

Robert L Champoux