Apparatus for attaching a fastener to sheet material

An apparatus is employed for forming an attachment of a threaded fastener or other item to a deformable sheet material by a clinching technique, preferably without shearing the sheet material in the area of the interlocking attachment of the fastener with the sheet material. As a result, a secure, interlocked, joint is formed to which other items can be threadably secured, with such joint being leakproof in some embodiments. Such leakproof fastener assembly is especially advantageous in the manufacture of fluid-containing products or other applications where a leakproof construction is necessary or desirable. In other embodiments, however, where such leakproof feature is not needed or is undesirable, the invention still provides an improved, secure, interlocked attachment of a fastener to a sheet material item, wherein the sheet material item is a single layer item or a multiple layer item.