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A strong, knurled collar, which is completely embedded in the sheet, guarantees against rotation of the fastener in the sheet. The spin resistance of the knurl greatly exceeds the torque that can be exerted by the self-locking feature.
When this collar is embedded in the sheet, the undercut cavity beneath the collar is filled with displaced sheet material thereby developing pushout resistance.
A dry-film lubricant applied to these fasteners provides the smooth, non-galling prevailing torque performance necessary for reliable locking and for reusability. In accordance with NASM25027 specifications, screws for use with PEM self-locking fasteners should be Class 3A/4h fit or no smaller than Class 2A/6g. Screws should be long enough so that at least two threads project through the PEM fasteners when tightened. |