Self-clinching nuts

PEM's SP-M3-1, intended for stainless receiving sheet, lists M3 × 0.5, 1.00 mm minimum sheet, a 4.22 +0.08 mm mounting hole and sheet hardness up to HRB 90 / HB 185. The stainless CLS-M3-1 instead lists HRB 70 / HB 125 and belongs to the steel-or-aluminum-sheet family. Select by host material, hardness and shank code as well as thread. SP-M3-1, CLS-M3-1.

What self-clinching means

A clinch nut is squeezed into a prepared sheet hole. Displaced host metal captures its retaining feature. PennEngineering, self-clinching mechanism.

PEM identifies the knurls as displacers and the ramped shank as a retention feature. PEM, Self-Clinching Technology.

Distinguish the attachment mechanisms

PEM's FAQ says ordinary self-clinching installation generally needs access to both sheet faces and a squeezing action; impact alone does not allow the required cold flow. It also identifies exceptions for some larger nuts. Those exceptions are not evidence that the M3 examples below support blind installation. PEM FAQ, installation access and squeezing

Read the complete part designation

The following are supplier catalog examples, not a generic design table. All dimensions are millimeters. Each column cites the exact PEM item whose HTML specification was read; no controlled CAD drawing revision was inspected.

The shank code is consequential even with the same thread: S-M3-2ZI lists A maximum 1.38 mm and recommended minimum sheet thickness 1.4 mm, while retaining the 4.22 mm hole listing and 4.8 mm centerline-to-edge minimum. “M3” alone therefore cannot select the shank. PEM, S-M3-2ZI

These fields describe separate boundaries: A is a fastener dimension; minimum sheet thickness is a host requirement; hole size is not thread diameter; centerline-to-edge distance is measured from the hole center, not its wall. The item-page footnote directs use of at least the specified centerline-to-edge value to limit sheet distortion. The HTML hole heading is reproduced above without inventing a missing lower-tolerance notation or hole-production specification. PEM, S-M3-1ZI specifications and footnotes

Material and process boundaries

PEM recommends its S/SS family for steel or aluminum sheets within the stated hardness limit. Its SP item explicitly targets stainless steel sheet. A stainless nut designation therefore does not, by itself, identify a nut for stainless sheet: CLS-M3-1 and SP-M3-1 have different materials and allowable sheet-hardness listings despite matching nominal geometry. HRB and HB are the supplier's listed hardness scales, not conversion rules established here. PEM, S family context, PEM, SP-M3-1 application

Ductility, hardness, thickness and corrosive environment all affect the design of the clinching features. Passing one hardness limit does not establish the other conditions. PEM, technology limitations

Material and finish also remain separate selections. PEM's FAQ identifies galvanic-corrosion potential for passive 300 series stainless fasteners in aluminum when electrolyte is present; acceptability depends on the application and the function of the interface. A passivation designation alone is not a corrosion-compatibility approval. PEM FAQ, stainless fasteners in aluminum

The manufacturer's mechanism illustration uses parallel punch and anvil faces. Tool access and support are therefore design inputs, but this page supplies no tooling geometry, force setting or installation sequence. PEM, mechanism and equipment illustration

Standards and evidence boundary

AIA's NAS/NASM Mailing 22-11, dated November 30, 2022, lists NASM45938/1, revision 3, titled “Nut, Plain, Clinch (Self-Clinching, Round),” with the memo's new-revision marker. The two-page public memo was read, including its page images. It is a publication notice, not the full standard; this research does not establish its detailed requirements, current amendment state or conformity of the commercial examples. AIA memo, pages 1–2

The supplier's ASTM and ASME references above are transcribed item attributes. Their editions are not identified by those item pages, and the full standards were not reviewed. The manufacturer HTML pages likewise expose no technical drawing revision or reliable technical publication date; their copyright footer is not treated as one.

Sources were retrieved on October 31, 2026 UTC, which was October 30, 2026 PDT in America/Los_Angeles; the reviewed date uses that local business date. Direct access to PEM's CL bulletin and handbook PDFs failed, and web screenshot calls did not expose usable page pixels. Their extracted text is excluded from the technical evidence used here. In particular, older PDF search results and live HTML show differing SP Brinell figures; the table preserves the exact SP-M3-1 HTML value rather than reconciling editions that were not visually inspected.

This draft establishes no universal press force, screw tightening torque, torque-out, pushout, capacity, service life, removal/reinstallation allowance or customer qualification. Hole preparation, coating sequence and production tooling remain outside its verified coverage. Those require the applicable supplier documents and evidence for the actual assembly.

Related reference

Hardware and component references provides neighboring process context; its existence is not application approval.