Fastener for Thin-Sheet Materials
A cylindrical, internally-threaded part such as a nut or standoff that can be clinched into very-thin, sheet-metal panel even if the receiving hole is blind. The part has no integrally-formed displacer. The part is installed in an annular, blind hole by cold deforming and pushing material of the panel with a special installation tool into one or more recesses of the part. The tool has an annular cavity for receiving the fastener, an annular displacer surrounding the outer diameter of the annular cavity, and a center punch surrounded by the inner diameter of the cavity. One recess of the part may comprise an undercut in the outer periphery while another recess may comprise the groove of the internal threads. With a single stroke of the tool, panel material is simultaneously pushed into the undercut by the displacer and into the threads by the center punch to attach the part to the panel by clinching.
1 . An assembly of a fastener attached to a blind hole in a sheet-metal panel, comprising;
a panel of sheet metal having an annular, blind receiving hole defined by an inner diameter, and outer diameter and a depth, said hole surrounding a central island of non-recessed panel material;
a fastener having a top end, a bottom end, a height, an outer periphery, a central bore with helical threads, and an undercut in said outer periphery located adjacent said bottom end; and
wherein the bottom end of the fastener occupies said hole and material of the panel occupies said undercut.
2 . The assembly of claim 1 , wherein panel material also occupies grooves of the threads.
3 . A method of assembling a member to a panel of sheet metal, comprising the steps of:
providing a panel of sheet metal having an annular, blind receiving hole defined by an inner diameter, an outer diameter and a depth, said hole surrounding a central island of non-recessed panel material;
providing a member with an undercut along its outside periphery adjacent a bottom end thereof;
placing at least a portion of the member in the hole; and
pressing a tool against the panel whereby material of the panel surrounding the member is forced into the undercut.
4 . The method of claim 3 wherein the member comprises a fastener having a top, a bottom, a height, and a central bore with helical threads.
5 . The method of claim 4 whereby the step of pressing the tool against the panel also forces material of the panel into at least one groove of the threads that extend from the top to the bottom along the entire length of the central bore of the fastener.
6 . The method of claim 3 wherein the tool does not press against the fastener.
7 . The method of claim 3 wherein the tool has a displacer at a bottom end thereof with an outwardly divergent bevel adapted to displace panel material into the undercut.
8 . The method of claim 4 wherein the tool has an annular cavity for receiving the fastener, said cavity having a height substantially greater than the height of the fastener.
9 . The method of claim 4 wherein the tool has center punch surrounded by the cavity and having a pointed end for displacing panel material outwardly into a groove of at least one of the threads simultaneously as material is forced into the undercut.
10 . The assembly of claim 9 , wherein the fastener lacks a displacer for forcing material of the panel into the undercut and the tool is the only means for displacing material of the panel against the fastener.