DESIGN FOR MANUFACTURING (DFM) GUIDE

Adding Threads to Sheet Metal

Sheet metal is too thin for conventional tapping. This guide covers the best methods for adding strong, reliable threads to your sheet metal assemblies.

The Challenge: Insufficient Material

The standard rule for a strong tapped thread in metal is to have at least 1x the fastener's diameter in thread engagement. Since sheet metal is typically only 1-3mm thick, it is impossible to create a durable, tapped thread directly in a standard hole. Attempting to do so would result in a thread with only 1-2 turns, which would strip out very easily.

To solve this, we must use methods that add more threaded material to the part.

A close-up of a tapped thread, illustrating the need for sufficient material depth

Best Methods for Threading Sheet Metal

Self-Clinching Hardware

This is the **most common and best method**. A self-clinching fastener (like a PEM® nut) is pressed into a precisely sized hole. The fastener's knurled shank displaces the sheet metal, causing it to cold-flow into a locking channel. This creates a very strong, permanent, and perfectly flush thread. We can install nuts, studs, and standoffs this way.

Weld Nuts

A weld nut is a special type of nut designed to be welded onto another metal object. For sheet metal, a nut with a flange can be placed over a hole and projection welded or spot welded in place. This provides a very strong connection and is ideal for heavy-duty applications.

Extruded Holes (Flow Drilling)

In this process, a special rotating tool is pushed through the sheet metal. The friction heats and softens the metal, allowing the tool to form a localized, taller collar or bushing from the parent material. This extruded collar is now thick enough to be tapped with a durable thread. This is a clean, strong method that requires no extra hardware.

Sheet Metal Threading FAQ

What is the minimum sheet metal thickness for installing a self-clinching nut?

This depends on the specific fastener size, but a general rule is that the sheet should be at least 1mm thick. Thinner sheets may not have enough material to properly cold-flow and lock the fastener in place.

How do I specify which hardware to install?

The best way is to use a callout on your 2D drawing. Specify the exact manufacturer's part number for the self-clinching nut or stud you require (e.g., "INSTALL PEM CLS-M3-1"). This ensures we use the correct hardware and create the correctly sized mounting hole for it.