You’ve designed a clean sheet metal enclosure. The geometry is solid, the bends are right, the material is spec’d. Then assembly starts — and you realize there’s nowhere reliable to thread a screw.
Sheet metal is thin by nature. That’s part of what makes it useful. But thin material means limited thread engagement, which means stripped holes, loose fasteners, and assemblies that don’t hold up in the field. Hardware insertion solves that problem before it starts.
Self-clinching fasteners — the category most engineers know by the brand name PEM — press permanently into your sheet metal parts and become part of the structure itself. The result is strong, clean, repeatable threads and mounting points that don’t require a nut on the back side, don’t rely on the sheet for thread strength, and don’t add bulk to your design.
This guide breaks down the main types of inserted hardware, when to use each, and what product designers and engineers need to know to specify them correctly from the start.
1. What Hardware Insertion Actually Is
Hardware insertion is the process of pressing threaded or functional fasteners permanently into a sheet metal part using a squeezing force — no welding, no adhesives, no secondary threads cut into the sheet itself.
The mechanics behind it are straightforward. The fastener’s shank is harder than the host material. When pressed into a precisely sized hole, it displaces the sheet metal through cold forming, causing the material to flow into locking channels or grooves on the fastener’s shank. The result is a fastener that resists both pushout and torque-out — held firmly in place not by friction, but by the physical interlock between the fastener and the displaced material.
This process is what makes self-clinching hardware so reliable. For many installed nuts, the screw itself will fail before the insert rotates or pulls out of the panel. That kind of strength in thin material is difficult to achieve any other way without adding significant complexity or cost to your assembly process.
The term “PEM fasteners” comes from PennEngineering, the company that pioneered self-clinching technology in 1942 and remains the most recognized brand in the category. In practice, the name PEM is used broadly across the industry to refer to self-clinching hardware regardless of manufacturer — much the way engineers refer to hook-and-loop tape as Velcro.
2. Self-Clinching Nuts: Reliable Threads in Thin Sheet
Self-clinching nuts are the most common type of inserted hardware, and for good reason — they solve the most frequent problem product designers encounter with sheet metal: how to create a strong, reusable threaded connection in material that’s too thin to tap directly.
A standard self-clinching nut installs flush on one side of the sheet and protrudes slightly on the other. Once installed, it provides full-depth threads that accept a standard machine screw, with no loose nut required on the back. The installed nut resists rotation from the serrated clinching ring that locks into the material during installation.
Several variations exist for specific design situations. Flush nuts sit completely flush on both sides of the panel — useful for cosmetic surfaces or areas where protrusion isn’t acceptable. Floating nuts have a small amount of thread movement built in, which is valuable when hole alignment between mating parts isn’t perfectly consistent and you need some forgiveness during assembly. Miniature nuts are designed for tight spaces and closer edge proximity than standard sizes allow.
One key design rule: nuts should be installed on the side opposite the bolt load. The screw should pull toward the sheet, not away from it. Installing on the wrong side dramatically reduces pullout resistance. It’s the kind of detail that’s easy to get right when you think about it early — and easy to overlook if hardware is treated as an afterthought.
3. Standoffs: Creating Space Between Components
Standoffs are threaded spacers that install permanently into sheet metal and hold two components at a fixed, precise distance. They’re one of the most practical pieces of hardware a product designer can work with, and they show up constantly in electronics enclosures, control panels, and anywhere a PCB or secondary panel needs to be mounted cleanly inside a larger assembly.
A through-hole standoff has threads running all the way through, accepting a screw from either end. A blind standoff is threaded on one end and closed on the other — useful when one end will be exposed and you don’t want an open hole. Both types press into the sheet using the same cold-forming process as self-clinching nuts, with the installed head sitting flush against the sheet surface.
The practical value of standoffs goes beyond just spacing. They eliminate the need to manage loose hardware during assembly — no separate nuts, no risk of a nut dropping into an enclosure during final build. They also provide consistent, repeatable spacing that doesn’t depend on assembly technique, which matters a lot when you’re moving from prototype into higher-volume production.
Imagine a product designer building a control enclosure that needs to house a PCB 10mm above the base panel. Using four installed blind standoffs at the correct locations means every unit gets exactly the same spacing — no shimming, no guessing, no variation unit to unit. That kind of dimensional repeatability is built into the design rather than dependent on the person assembling it.
4. Self-Clinching Studs: Fixed Male Threads for Cleaner Assemblies
Where nuts accept a screw, studs provide one. A self-clinching stud installs flush on one side of a sheet metal panel and presents a permanently fixed male thread on the other, eliminating the need to handle a separate bolt during final assembly.
Studs are particularly useful when multiple components are being stacked and secured with the same set of fasteners. Consider an assembly where a base panel, spacers, a PCB, more spacers, and a cover plate all need to be secured together. Installed studs on the base panel let you stack all the components and tighten a single set of nuts at the end — no one holding a bolt from underneath while someone else tightens from the top.
Flush head studs sit completely flat on the installation side of the panel, which keeps the back surface clean and snag-free. This is especially relevant for panels that slide into enclosures or stack tightly against other surfaces.
Like all self-clinching hardware, studs require that the host material be softer than the fastener. For most mild steel, stainless, and aluminum applications this is straightforward — but stainless steel panels require fasteners specifically rated for that material, as the hardness difference is much narrower and standard fasteners won’t clinch properly.
5. Design Considerations That Make or Break Hardware Performance
Specifying the right fastener type is only part of the equation. Where and how you place hardware in your design has a direct impact on whether it performs as intended — and whether your fabricator can even install it.
Edge distance is one of the most important constraints. Every fastener has a minimum distance from the centerline of its mounting hole to the nearest edge of the sheet. Install too close to an edge and the material doesn’t have enough mass to cold-flow properly during clinching — the result is a bulged or deformed edge, and a fastener that isn’t fully locked in. The specific minimum distance varies by fastener size and type, and is listed in each manufacturer’s spec sheet.
Proximity to bends is equally important. Sheet metal stretches during forming, and hardware holes near bend lines can distort during the brake process — changing the hole diameter just enough to prevent the fastener from clinching correctly. The general guidance is to keep hardware holes a minimum distance from any bend line, usually expressed as a multiple of material thickness. When a design truly can’t accommodate that spacing, hardware can sometimes be installed after forming, though that adds cost.
One more practical note: don’t deburr hardware mounting holes before installation. It seems counterintuitive, but the small amount of material at the hole edge is exactly what flows into the fastener’s locking channel during clinching. Removing it reduces the strength of the installed connection.
6. Specifying Hardware Correctly on Your Drawings
A well-designed part with poorly specified hardware callouts creates problems downstream — wrong fastener ordered, wrong installation side, wrong hole prep. Getting the callout right is simple once you know what information is needed.
Hardware should be called out on the drawing with the full manufacturer’s part number, the installation side, and the quantity. For example: “INSTALL PEM CLS-M4-2, NEAR SIDE, 4 PLACES.” The part number tells the fabricator exactly which fastener to use. The installation side tells them which face of the sheet the fastener head should be on. Quantity eliminates any ambiguity.
Using standard in-stock sizes wherever possible is worth emphasizing. Custom or unusual fastener sizes can introduce lead time and cost that a small design change could easily avoid. Most fabricators stock a range of common thread sizes in both inch and metric — designing around those sizes keeps your supply chain simple and your lead times short.
Finally, it’s worth aligning hardware selection with your finish schedule. PEM hardware should generally be installed before painting or powder coating, not after. Installing into a finished panel can damage the surface around the insert, and coatings on the mounting hole itself can interfere with the clinching process. If your part is going through a finish process, flag that early so the sequence is built into the workflow from the start.
7. Work with a Fabricator Who Gets the Details Right
Hardware insertion looks simple on paper — press a fastener into a hole, move on. In practice, the details matter a lot. Hole size precision, installation force calibration, correct tooling for each fastener type, and installation sequencing relative to forming and finishing all affect whether the finished part performs the way it was designed to.
A fabrication partner with real hardware insertion experience will catch problems at the design stage rather than the production stage. They’ll flag edge distance violations in your drawing before cutting starts, recommend in-stock fastener sizes that shorten your lead time, and ensure hardware is installed in the right sequence relative to bending and finishing. That kind of upstream collaboration is what separates a smooth production run from one full of rework.
When you’re ready to move a design forward — whether it’s a prototype or a production run — the EMS team is ready to help. We’ll review your hardware callouts, confirm your design is set up for clean installation, and make sure the finished parts are built to perform. Reach out here to get started.