Self-clinching standoffs

Captive's CFSOS M3-8 through-threaded and CFBSOS M3-8 blind-threaded standoffs list M3 × 0.5, 8 +0.05/−0.13 mm length, 1.0 mm minimum sheet and 4.22 +0.08/−0.00 mm round mounting hole. The blind version’s thread depth is a separate drawing field. Check screw engagement and bottoming separately from the installed spacing. Captive catalogue p. 73, through-threaded, p. 76, blind-threaded.

Scope and retention mechanism

A self-clinching standoff captures a spacing barrel in a prepared sheet hole by displacing sheet material. Captive, Proper Use of Captive Standoffs, p. 1.

A loose spacer, bonded standoff or PCB support can provide spacing without the same clinching mechanism. Captive, Proper Use of Captive Standoffs, p. 1.

Check installed spacing, thread engagement and load against the applicable assembly drawing.

Fastening-family distinctions

Captive separates self-clinching fasteners for ductile materials from broaching fasteners for nonductile materials. The former depend on displaced sheet material entering an undercut; the latter are retained by an interference fit. These different retention mechanisms do not establish shared hole or host-material requirements. Captive catalogue, p. 5

PennEngineering likewise lists KFE/KFSE as broaching standoffs and KFB3 as a flare-mount standoff under its PC-board/nonductile-material category. Their appearance in a standoff catalogue does not make them sheet-metal self-clinching substitutes. This source is a category listing, not evidence for a specific broaching or flaring assembly's dimensions or loads. PEM, fasteners for PC boards and other nonductile materials

Blind, through-threaded and unthreaded variants

The first two families are shown on Captive catalogue pp. 71 and 74; the blind dimensional section is on p. 74. The unthreaded family is separately identified on p. 86.

Here, blind describes the closed thread cavity; it does not establish a one-sided installation-access requirement. Captive blind-standoff section, p. 74

Captive's threaded-part key separates series, an optional body code, thread code and length code. Its unthreaded key instead uses a body/hole code. For example, the metric M3 and 3.5M3 threaded rows both have M3 × 0.5 threads but different body and hole dimensions. Neither a body/shank code nor a length suffix defines a generic host-sheet grip range. Captive catalogue, part keys pp. 71, 86 and metric rows p. 73

Host material, hardness and finish

The following limits are the inspected Captive series recommendations, not a rule for every self-clinching standoff:

These are taken from Captive catalogue p. 71 and p. 74. Hardness refers to the material receiving the fastener; it is not the fastener's hardness or a thread proof-load class. The stainless fastener material designation alone does not qualify use in stainless host sheet. The source's ASTM designation has no edition stated here; no full ASTM standard was inspected.

The finish table distinguishes clear zinc ZI from zinc with clear chromate and sealer ZS. These designations identify distinct listed zinc finishes. No corrosion lifetime or environmental qualification is inferred. Captive catalogue, finish key p. 6

Bounded metric dimensional examples

The following rows are catalogue selections, not current controlled manufacturing drawings or cross-brand equivalence claims. All dimensions in this table are millimetres.

The rows and length selections are on Captive catalogue p. 73, through-threaded and p. 76, blind-threaded, with material conditions above. The minimum sheet field is a lower limit, not an unlimited-thickness or universal grip-range approval. H identifies the hex dimension, not a hexagonal mounting-hole requirement. Overall length, available spacing, thread engagement and host-sheet thickness are distinct physical quantities.

What performance data establishes

Captive's push-out bulletin describes an axial loading fixture with a supported test strip and clearance for standoff movement. It states that push-out and torque-out results describe holding strength in the sheet; they do not establish thread axial strength, permissible tightening torque or assembly design loading. The fixture and failure mode limit the applicability of the holding-strength results. Captive, Standoff Performance Testing: Push-Out Testing, p. 1

The torque-out bulletin describes pure-torsion testing without axial load between the fastener and test panel, with the parent test strip held firmly. A mating screw that clamps parts together creates a different condition. Torque-out is therefore not a screw-tightening prescription. Captive, Standoff Performance Testing: Torque-Out Testing, p. 1

The catalogue's metric performance table is specifically headed 1.5 mm 5052-H34 aluminium and 1.5 mm cold-rolled steel, with separate installation-force, push-out, torque-out, pull-through and maximum recommended tightening-torque columns. It also marks aluminium standoffs in the cold-rolled-steel condition as not recommended. The table does not establish performance for the 1.0 mm minimum-sheet dimensional examples above or for another sheet alloy or temper. This draft reproduces no numerical performance or installation values. Captive catalogue, p. 77

Application relationships and coverage limits

Overall standoff length, blind-thread depth and host-sheet thickness describe different assembly dimensions. The catalogue separates length L, minimum thread depth T, body/hole geometry and the host-sheet minimum; a shared thread designation does not establish equivalent spacing or engagement. Captive catalogue, through-threaded p. 73, blind-threaded p. 76

Supported-component seating and load direction also affect the load path through the clinch and head. Captive's cautions about side force and a gap beneath the supported panel concern those interfaces; they supply no numerical side-load or bending capacity. Captive, Proper Use of Captive Standoffs, p. 1

The inspected dimensions, host-material recommendations and test descriptions cover specified catalogue families and test conditions. They do not establish a current production drawing, application-specific installation qualification or acceptance criterion. No generic side-load capacity, thread strength, stainless-host compatibility or customer qualification is established here.

Source versions and access limits

Review and retrieval date: 2026-10-30 PDT, America/Los_Angeles. Retrieval is separate from source publication or revision.

• Captive Self-Clinching Fasteners catalogue: the downloaded 111-page manufacturer PDF carries copyright 2020 on PDF p. 2 and 2020 on the cited catalogue pages. A separately printed current revision identifier and exact publication day were not established. The cited sections and drawings were visually inspected, not the entire catalogue. PDF metadata modification dates do not establish a controlled revision. Catalogue identity, p. 2
• Captive technical bulletins: the three one-page bulletins are identified by their titles above. No publication date or revision identifier is printed on the inspected pages. Their full pages, including diagrams and caveats, were visually inspected.
• PEM category listing: undated HTML; used only to distinguish named broaching and flare-mount families. Initial PEM standoff PDF/tech-sheet URLs returned empty HTTP 202 bodies during direct retrieval, so no dimensions or engineering claims rely on those inaccessible documents or their search extracts.

No full ASME, ANSI, ASTM or other standard was inspected. No catalogue drawing here is represented as an approved current production drawing.

Related reference

Hardware and component references supplies adjacent process context; it does not qualify these parts or assemblies.