Self-Clinching/Metal Inserts/PEM

Self-clinching (PEM) inserts press-fit into sheet metal to add durable threads or studs without welding, using localized cold forming.

Overview

Self-clinching fasteners (often called PEM inserts) are press-installed hardware—nuts, studs, and standoffs—that cold-form into sheet metal under a controlled force. The insert displaces material into an undercut, creating high torque-out and push-out resistance while keeping the sheet surface flush on the bearing side. Installation is typically done after punching/laser and before finishing, using an arbor press or insertion press.

Choose PEM insertion when you need repeatable threads in thin sheet, fast assembly, and serviceable joints (unlike many tapped thin-wall threads). It works best in ductile sheets and with accessible press tooling.

Tradeoffs: you need correct hole size and edge distance, access to both sides (or specific one-sided types), and adequate sheet thickness/hardness range for the fastener spec. Mislocated holes, burrs, coatings before insertion, or very hard/soft materials can cause spin-out, poor seating, or cosmetic distortion.

Common Materials

  • Aluminum 5052
  • Aluminum 6061
  • Stainless Steel 304
  • Cold Rolled Steel
  • Galvanized Steel
  • Mild Steel

Tolerances

±0.005"

Applications

  • Threaded attachment points in electronics enclosures
  • Stud mounting for panels and access covers
  • Standoffs for PCB mounting in sheet metal chassis
  • Captive nuts in HVAC and appliance panels
  • Grounding studs and bonding points in electrical cabinets
  • Threaded inserts in brackets and sheet metal frames

When to Choose Self-Clinching/Metal Inserts/PEM

Pick PEM inserts when the part is thin sheet and you need strong, reusable threads or studs with fast assembly and consistent hardware location. It fits low to high volumes because insertion is quick and scalable with dedicated tooling. Best results come from controlled hole features, clean surfaces, and good press access.

vs Riveting

Choose PEM inserts when you need threaded attachment points (nuts/studs/standoffs) rather than a permanent lap joint. Clinch inserts support repeatable assembly/disassembly and keep hardware captive without loose nuts or back-side wrenching. Rivets usually win for simple permanent joints where threads aren’t required.

vs Welding (weld nuts/studs)

Choose PEM inserts when you want to avoid weld spatter, burn-through, distortion, and post-weld cleanup on thin sheet. PEM installation is faster for mixed materials and maintains coating plans more cleanly when inserted before finishing. Welding can outperform when you can’t meet clinch material/thickness requirements or need one-sided installation in very restricted access.

vs Tapping (threading directly into sheet)

Choose PEM inserts when sheet thickness is too low to hold adequate thread engagement or when you need better strip resistance over repeated cycles. Inserts provide hardened, standardized threads and reduce variability from forming/tapping burrs. Direct tapping works for thicker sections or low-load, low-cycle assemblies.

vs CNC machining (adding threaded bosses)

Choose PEM inserts when the core part is sheet metal and you want threads without adding machined blocks, PEM plates, or welded bosses. Inserts keep the BOM light and assembly fast while holding tighter functional thread performance than thin-wall tapping. Machined bosses make sense when you already have a machined part or need thick, structural threaded features.

Design Considerations

  • Call out the exact fastener family and size (e.g., nut/stud/standoff, thread, material, finish) instead of “PEM” generically
  • Dimension and tolerance the installation hole per the fastener datasheet; hole size and roundness drive torque-out performance
  • Maintain minimum edge distance and spacing between inserts to prevent bulging, cracking, or distortion during pressing
  • Specify insert installation before painting/powder coat/anodize unless using hardware intended for post-finish installation
  • Ensure press tooling access and a flat bearing surface around the hole; avoid bends, louvers, weld seams, or embosses in the seating area
  • Control burr direction and deburr the bearing side so the fastener seats flush and doesn’t rock or spin