Guide
PEM inserts and hardware: how to call them out so the sheet metal shop installs them right
Self-clinching hardware, which most people call PEM hardware after the brand that popularized it, is how a sheet metal enclosure gets a thread it can be bolted to without a weld nut or a loose nut on the back. The parts are pressed into a punched hole and the sheet cold-flows into a groove. They are cheap and fast when the drawing calls them out properly, and a source of rework when it does not.
Send a drawingUpdated October 8, 2026
The common parts
| Part | What it gives you | Typical use |
|---|---|---|
| Self-clinching nut | A threaded hole in thin sheet | Covers, panels, anything bolted from one side |
| Self-clinching stud | A threaded post standing off the sheet | Grounding points, hanging a sub-panel |
| Standoff | A threaded or through spacer | Mounting a circuit board or a plate at a set height |
| Flush nut | A thread that sits flush with the sheet | Where the back face must stay flat |
| Floating nut | A nut with a little play | Where mating holes will not line up exactly |
| Panel fastener | A captive screw | Access panels opened often |
How installation works, and why thickness matters
The shop punches or laser-cuts a hole to the manufacturer's specified size, then presses the part in with a press that squeezes it to a set force. The sheet material must be softer than the fastener and at least as thick as the part's minimum sheet thickness. A part specified for 0.060 inch minimum pressed into 0.040 inch sheet will spin or pull out. The manufacturers publish the minimum sheet thickness and the hole size for every part number; the shop reads the part number on your drawing and looks those up.
That is the single most useful thing you can do: put the manufacturer's full part number on the drawing, with the side it installs from. CLS-M4-2 says the thread, the material and the shank length; a note that says "M4 PEM nut" does not.
Hardware and finishing
Powder coat and paint fill threads, so most shops install hardware after finishing, with the hardware holes masked or simply pressed through the coating. Zinc plated hardware pressed into a steel part that is then plated gets plated over, which is usually fine for a nut and bad for a fine thread. Stainless hardware in aluminum sheet is a corrosion couple in a wet environment; say which environment the part lives in and the shop will suggest the right material.
If the part is anodized, hardware goes in after, because anodizing is an acid bath that attacks steel inserts. Say it on the drawing if you want the hardware in before a coating for a specific reason.
Design rules that avoid rework
- Keep the hardware away from bends: a minimum edge distance from the bend line is published for each part, usually a few sheet thicknesses, or the bend distorts the hole.
- Keep hardware away from each other and from the sheet edge for the same reason.
- Install hardware from the side the shop can reach with the press: a nut inside a closed box is a problem if the part is formed first.
- On a part with many of the same hardware, say the count on the drawing: the shop orders them by the box and prices the pressing per piece.
Questions buyers ask
- Can I ask for a weld nut instead?
- Yes, and for thick sheet or structural loads it is the better part. For sheet under about 0.100 inch a self-clinching nut is faster and cleaner. Say which you want; the shop quotes what is drawn.
- Do I supply the hardware?
- No. The shop sources it by part number and includes it in the quote unless you say otherwise. If you have a preferred brand or a stock of hardware, say so on the request.
- What if the drawing says PEM but the shop uses another brand?
- Self-clinching hardware from the main brands is interchangeable by part number. If the exact brand matters, write "no substitutes" on the drawing and the shop quotes that part.
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