What Is PEM Hardware and When Should You Use It Instead of Tapping a Hole?

PEM hardware is press-in fastener inserts, nuts, studs and standoffs that get seated into a punched or drilled hole under pressure, so the insert carries the thread instead of the sheet material being tapped directly. Use it when the sheet is too thin to hold a reliable tapped thread, or when the part gets assembled and disassembled more times than bare sheet metal thread can survive.

Why tapping thin sheet is the problem

A tapped thread needs enough engaged length to hold torque without stripping. In thick plate that's easy. Three or four threads of engagement in steel holds up fine.

In sheet metal, especially anything under about 2 mm, you run out of material before you get meaningful thread engagement. The first few bolt cycles might hold. Then the threads round out and the fastener spins free in the hole.

That failure mode doesn't announce itself gradually. It works, and then one day it doesn't.

PEM-style inserts solve this by moving the thread engagement off the sheet thickness entirely. The insert has a barrel or flare that presses into the hole and locks in place with knurls or a broach that bites into the surrounding material. The thread lives inside that insert, with full engagement length regardless of how thin the parent sheet is.

When tapping the sheet is still fine

If the sheet is thick enough to give real thread engagement, and the fastener only gets installed once or twice over the life of the part, a straight tapped hole is simpler and cheaper. Adding hardware means an extra insertion operation and a part number to track. Don't reach for PEM inserts as a default. Reach for them when thickness or duty cycle actually calls for it.

The other case where tapping doesn't make sense at all is very thin sheet where there isn't enough material to hold a thread no matter how careful the tap is. That's not a technique problem. It's a geometry problem, and hardware is the fix.

What to plan for on the drawing

Insert hardware needs a hole sized to the manufacturer's spec for that part number, not just a tap-drill-sized hole. It also needs to go in before the part is fully formed if it sits near a bend, since the insertion press needs a flat surface to seat against.

Call out the insert part number and location clearly. Don't assume the hole for a press-in nut is interchangeable with the tap drill size for the same thread. They're usually different diameters entirely.

DigiForge runs PEM insertion as one of our three sheet metal operations, alongside laser cutting and press-brake forming, on cold rolled steel, galvanized steel, aluminum 5052, aluminum 6061, stainless 304 and stainless 316. If you're not sure whether your sheet thickness supports a tapped hole or needs an insert, flag it before the file goes out rather than finding out after the first assembly cycle.

Thin sheet and repeated assembly point toward hardware. Thicker sheet and one-time assembly point toward a tapped hole. Match the fastening method to how the part actually gets used, not just to what's easiest to draw.