Self-Clinching/Metal Inserts/PEM

Self-clinching/PEM insertion embeds reusable threads or studs into thin sheet metal, creating high-strength, flush, permanent fastening points in soft or ductile sheets.

Overview

Self-clinching inserts (often called PEM fasteners) are pressed into pre-punched sheet metal holes, displacing material into an undercut to lock the fastener in place. They provide strong, reusable threads, studs, or standoffs in sheet metal that is too thin for tapping, while keeping one or both sides flush for tight packaging and cosmetic surfaces.

This process suits medium to high volumes where you want consistent hardware installation directly in the fab shop, not on the assembly line. It offers excellent pull-out and torque resistance with minimal added thickness, but does require compatible sheet material, controlled hole sizes, and access for a press. Wrong hole size, incorrect sheet thickness, or inserts too close to bends/edges will cause spin-out, sheet distortion, or rejects. Use PEM insertion when you want clean, robust, integrated fastening points in production sheet metal parts with predictable assembly behavior.

Common Materials

  • Mild steel sheet
  • Stainless steel 304
  • Aluminum 5052
  • Aluminum 6061
  • Copper sheet
  • Brass sheet

Tolerances

±0.005" location relative to datums

Applications

  • Electronics enclosures with internal threaded bosses
  • Server and telecom chassis with captive hardware
  • Battery packs requiring flush studs or nuts
  • Instrument panels with mounted switches and connectors
  • Sheet metal brackets needing strong threads in thin sections
  • Medical device housings with clean external surfaces

When to Choose Self-Clinching/Metal Inserts/PEM

Choose self-clinching inserts when you need strong, repeatable threads or studs in thin sheet metal that cannot be reliably tapped. Ideal for production sheet-metal parts where you want permanent, flush hardware installed during fabrication for fast downstream assembly. Best suited to ductile sheet materials and consistent volumes where press tooling and setup are justified.

vs Riveting

Prefer self-clinching inserts when you need robust, reusable threads or precise stand-off heights rather than simple sheet-to-sheet joining. PEM hardware integrates the fastening feature into the sheet, reduces loose hardware count, and improves serviceability where assemblies will be taken apart multiple times.

vs Tapping in sheet metal

Choose self-clinching inserts when sheet thickness is less than about 2–3× thread pitch or you need higher strip-out strength. PEM hardware gives more durable threads, better torque resistance, and less risk of cross-threading or stripping during assembly.

vs Weld nuts

Use self-clinching inserts when you want clean cosmetics, minimal distortion, and no welding heat-affected zone. PEM inserts avoid weld spatter, reduce post-weld rework, and work well on thin or pre-finished material where welding is risky.

vs Thread-forming or self-tapping screws

Select self-clinching inserts when assemblies will be frequently serviced or subjected to higher torque, where thread-forming screws could eventually strip the sheet. PEM hardware stabilizes alignment and torque performance while allowing the use of standard machine screws.

vs Spot welding for brackets or studs

Use self-clinching studs or standoffs instead of spot-welded hardware when you need controlled stand-off height, tight positional accuracy, and better pull-out strength in thin sheet. PEM hardware also simplifies quality inspection since seating and clinch quality are easy to verify visually.

Design Considerations

  • Specify the exact PEM part number, material, and installation side on the drawing to avoid hardware or orientation mistakes
  • Keep inserts away from bends, hems, and edges; follow manufacturer minimum distances and provide flat, unsupported land around each hole
  • Dimension hole diameters and tolerances to the PEM datasheet; oversized or undersized holes cause spin-out or sheet distortion
  • Match sheet thickness and material hardness to the specific insert series; using outside the recommended range leads to poor clinch strength
  • Avoid placing inserts over welds, joints, or features that stiffen the sheet locally, which prevents proper material flow into the clinch undercut
  • Call out critical positional tolerances to datums only where needed; over-constraining insert locations can drive unnecessary cost and inspection time