Installation

Many of the recent failures of the MS21042 series can be attributed to improper installation of the fastener. Over-torquing or improper selection of the male fastener threads can result in galling.

Galling is a form of adhesive wear that can occur in fasteners as they are tightened. As the fastener tightening continues, these localized cold welded joints shear, tearing off metal particles. Debris and particles from the sheared joints film are entwined in the sliding surfaces which exacerbate the adhesive wear. The process can ultimately lead to seizing of the fasteners and breakage if tightening continues. Seizing can even occur during the loosening process.

With today's use of high speed, high powered torque wrenches, the considerations to avoid galling are increasing necessary.

Galling is best prevented by:

Another common cause of failure of the MS21042 series due to installation is 'shanking' of the nut by the male fastener. This is caused by an improper selection of the male fastener length, which allows the body of the fastener to 'shank out' the threads of the nut. As a result of this possibility, the male fastener should not be installed with no more the two or three threads past the nut.