A Guide to Sheet Metal Clinching for HVAC Contractors

The goal is to answer common questions an HVAC operations leader might have when considering clinching as an alternative fastening method.

What is clinching, and how does it work?

Clinching is a mechanical joining process for sheet metal that forms a strong interlocking bond without any fasteners (no bolts, rivets, or screws) and without welding. 

Instead of heat, clinching uses a punch and die to deform the metal sheets together and create a button-shaped joint. This process is widely used in industries like HVAC, automotive, and appliance manufacturing, where thin metal sheets need to be joined quickly and reliably.

How the clinching process works: 

1. Two or more sheet metal layers are placed on top of each other and inserted between a matching punch and die tool. 
2. When the machine is activated, the punch drives the top sheet into the bottom sheet and into the die cavity, squeezing the metals together. 
3. The pressure causes the lower sheet to plastically flow around the upper sheet, creating a locked “button” joint that holds the layers firmly. All of this happens very fast – the entire punch-and-form cycle completes in about one second or less. 
4. Once the punch retracts, the joined sheets can be removed, now clinched together permanently.

This simple technique works well with typical HVAC sheet metals like galvanized steel or aluminum. It can even join dissimilar metals or sandwich a layer of non-metal (for example, a seal or insulation layer in a duct joint) in one press stroke. The result is a secure joint without adding any pieces or applying any heat.

Strength and durability of clinched joints

A common question is whether a clinched joint is as strong as a welded joint. In general, clinched joints are very strong for sheet metal applications, but they are not quite as strong as a quality spot weld. In fact, a clinched joint is typically about 50% as strong as a comparable spot weld. This means if ultimate tensile or peel strength is critical (for example, in heavy structural assemblies or very thick material), traditional welding might still be the better choice.

However, for most HVAC components, maximum strength is not a concern. To illustrate the strength of clinching joints, we like to say that two pieces of 20 gauge clinched together with a single clinch could support two grown men – or roughly 430lbs – in shear.

Because clinching doesn’t melt the metal or change its overall geometry, it often yields more uniform results with less distortion compared to welding. In practical terms, a well-formed clinch can hold duct panels or sheet metal parts securely through vibration and handling over the lifetime of HVAC equipment. Operations leaders should evaluate their specific strength requirements: if the sheet metal assembly doesn’t require the full strength of a weld, clinching can likely meet the need while providing other benefits. 

Production speed and efficiency

In a production environment, throughput speed is critical. Clinching offers an advantage here with its high cycle rates. Each clinch joint can be formed in under a second, and the process can often be faster overall than spot welding for several reasons. First, there is minimal setup and repositioning time – operators simply position the sheets and activate the press. 

Spot welding is also a fast process per weld, but it can require time for proper alignment, electrode adjustment, and occasional cooldown periods. Clinching machines, by contrast, can maintain rapid cycling without the need for cooling pauses because no heat is generated. 

Furthermore, multiple clinching heads or portable clinchers can be used simultaneously on large assemblies to further speed up production. For an operations leader, this means the potential to reduce assembly time and increase output on the shop floor by adopting clinching technology.

Joint appearance and finish quality

Another consideration is the finish quality of the joint, especially for visible HVAC components or where post-processing is an issue. Clinching is a clean process – it produces a button-like dimple at the joint but no burn marks, discoloration, or splatter. There is no “heat-affected zone” that alters the metal’s coating or surface. 

This is a big advantage if you are working with pre-galvanized or pre-painted sheet metal, common in HVAC products. A weld can burn off protective zinc coatings or paint, leaving a scar that may rust or require touch-up. In contrast, clinching preserves galvanized and painted coatings during joining, so the corrosion resistance and finish remain intact.

Equipment maintenance and operating costs

Maintenance is an often overlooked factor when comparing joining methods. Clinching equipment tends to have low maintenance requirements. The clinching tools (punch and die) are durable and can make tens of thousands of joints before needing refurbishment or replacement, depending on the material and thickness. There are no consumable electrodes or filler materials as there are in welding. 

Spot welding electrodes degrade with use and need regular dressing (grinding to maintain shape) or replacement, and the welding machinery often requires a water cooling system to keep the tips and transformers from overheating. 

All of that maintenance means more production downtime over the long run and ongoing costs for parts and utilities.

With clinching, there’s no coolant, no welding wire, and no shielding gas – just the occasional punch/die replacement and basic machine upkeep. This translates to minimal downtime and lower operating costs for the shop.

Operator skill and training requirements

When comparing clinching to spot welding, it’s important to look at the practical skill level needed on the shop floor.

Spot welding doesn’t require mastery of an arc or molten puddle (as in MIG or stick welding), but it still demands careful technique. Operators must position electrodes precisely, manage timing and pressure, and ensure consistent contact and alignment to achieve good weld quality.

Clinching, by contrast, is generally much easier to learn and execute. Operators position the sheet metal, activate the machine, and the tooling forms a consistent joint with little variation. Because it’s a cold-forming process, there are fewer parameters to control—no voltage, no current, no electrode alignment. This makes it faster to train new employees, easier to cross-train existing ones, and more forgiving in production environments.

Automation readiness

With the HVAC industry facing growing pressure to increase throughput and reduce labor reliance, automation readiness is a key consideration.

Clinching is highly compatible with automation. It requires no consumables, no heat, and no active process monitoring (like voltage or current), which simplifies integration with robotic systems. Process monitoring can be used to detect when a tool has broken or a poor clinch has been made – but it isn’t required. A robotic arm can be easily programmed to position sheet metal and trigger the clinch cycle, or move a portable clinch tool into position if the part is large or difficult to fixture — no need to monitor weld nugget quality or change electrodes between parts.

Is clinching right for your HVAC shop?

Clinching is an innovative sheet metal joining method that offers HVAC manufacturers a combination of speed, efficiency, and safety. It creates robust joints in galvanized steel or aluminum without the downsides of welding – no heat distortion, no fumes, and minimal skill barriers. 

While a clinched joint isn’t as strong as a weld, it is more than strong enough for most ductwork, cabinets, and other HVAC assemblies. The process shines in its ease of use and consistency, making it an attractive option for operations leaders looking to improve production workflows.

In summary, if you’re considering alternatives to spot welding or traditional fastening in your HVAC fabrication line, clinching is worth a close look.