Because thin sheet gives one or two threads of engagement, which strips at almost any torque.

Thread engagement is what carries load, and it is a function of material thickness.

A clinch nut provides full engagement in material far thinner than the thread is long.

It does so without welding, without heat and without damaging the panel finish.

Extruded or dimpled holes are the alternative and give more engagement than a plain tapped hole, but still less than a clinch nut.

Weld nuts are the other option and bring heat distortion and finish damage with them.

The fastener must be harder than the sheet, the sheet must meet a minimum thickness, and the hole must be the specified diameter.

The mechanism is panel material flowing into an undercut and a knurl, so the fastener has to be the harder of the two.

Clinch fasteners are supplied in grades matched to aluminium, mild steel and stainless panels for exactly this reason.

Below the minimum sheet thickness there is not enough material to displace.

An oversized hole leaves too little material; an undersized one deforms the panel rather than flowing.

Get any of the three wrong and the fastener looks installed while spinning or pulling out in service.

With a press applying a specified force squarely through parallel platens - never with a hammer.

The force is stated by the manufacturer for each size and material combination.

Steady, controlled pressure lets the panel material flow into the fastener's features.

An impact delivers an uncontrolled impulse, dishes the panel and leaves a partly formed clinch.

The fastener must also be square to the panel, since a tilted installation reduces both pull-out and torque resistance.

Bench and hand-lever presses sized for clinch fasteners are the correct tooling.

Not without damaging the panel - the installation is permanent by design.

Removing the nut tears the displaced panel material that was holding it.

The resulting hole is enlarged and deformed and will not accept a replacement of the same size.

A larger clinch fastener sometimes recovers the position if the hole can be cleaned up accurately.

Otherwise a different fastener type is fitted at that hole.

For panels that may be reconfigured, a bolted or cage nut arrangement is more appropriate.

The side the manufacturer specifies - it is not arbitrary, and punched holes have a preferred face.

A punched hole is slightly tapered, with a cleaner edge on the punch side.

The fastener is installed from the side that presents the correct hole geometry.

The head or flange finishes flush on one face, which determines which side the assembly sees.

Flush-on-both-sides versions exist where neither face may carry a protrusion.

Getting the direction wrong reduces the clinch strength even when everything else is correct.

A blind nut is closed at the far end, sealing the panel and limiting screw length; a through nut is open and more tolerant.

Blind versions stop dust, liquid and contamination passing through the fixing.

They also prevent a screw protruding into a space where it would foul something.

The closed end means a screw that is too long bottoms out and clamps nothing while feeling tight.

Through versions accept any screw length beyond the minimum engagement.

Where the panel separates two environments, blind is usually the correct choice.

Volume sheet metal work - enclosures, chassis, control panels, rack equipment and appliances.

Anywhere a threaded mounting point is needed on sheet too thin to tap.

They remove loose parts from the assembly line, since nothing is held behind the panel.

Service is easier because the thread stays when the component is removed.

They suit manufacture where a press is available and positions are fixed by design.

For one-off work or changeable positions, cage nuts or bolted arrangements are more practical.