What is a Pinch Weld? When does it make sense to use it?

Last Updated on Apr 17, 2022

Many people think they know what pinch weld is but may not have a clear idea. Most think it’s the sealant you put on a zip slide. Pinch welds are sometimes referred to as herringbone welds because they resemble the bones in a fish. Many mechanical and aircraft engineers use pinch welds to make aircraft and vehicles more structurally sound and waterproof.

Pinch welding is a solid adhesive technique to fix metal plates closely together. When someone finds that they need it done, engineers in the field often answer questions about pinch welds. This blog post will tell you what you want to know about a pinch weld and where you can use it.


A simple explanation  – Pinch Welding

A pinch-weld is one of the strongest welds because it creates a mechanical bond between metal panels or sheets. You will mostly find it on safety equipment, steel buildings, bus bodies, and other transportation structures. A pinch effect on metals results from electrostatic attraction between charged particles.

The pinch weld, also called butt joint, is an assembly technique in which two fitting halves are screwed or otherwise made to fit tightly together. A pinch weld seam separates the metal or composite panels.The automotive industry uses this technique commonly during assembly.

With advances in structural material development over the last few years, specific plastic combinations with higher fatigue resistance have specialized engineering properties. These properties allow structures with fewer total length members to save weight, cost, and assembly time. You can reinforce a pinch weld to make it stronger.


3 Main Types of Pinch Welds

Flat shaped pinch welds

Flat-shaped pinches are one of the simplest types of welding joints to create. These welds join long pieces of metal horizontally to cover the car machinery.

L-shaped pinch welds

It’s the most common type of welding used for automobile manufacturing. You usually see the L-shaped welds running underneath the length of your vehicle. For this type of welding job, the welder uses two pieces of sheet steel that he must put together.

One of the metal pieces has an L shape. This position means that this piece of steel will stand upright strictly at 90°. You will place the second piece of metal horizontally across from the first one. Then he lays them next to each other. Then they use the spot welding process to attach them.

After completing the welding process, they apply an adhesive to the spot-welded joints. Your final project will be an L-shaped joint. There will be a metal piece protruding at the bottom of your car, near where the wheel meets the body.

 Z-shaped pinch welds

To create a Z-shape pinch weld, join two L-shaped pinching joints together. It’s the most challenging kind of pinch welding to perform because almost two L-shaped pinched connections need to become one single connection. A welding technician will construct two pieces of metal into one piece by building them together diagonally.

We see this type of pinch weld at the front top of a vehicle, creating both the windshield or windscreen structure and the windows. To make the necessary structural strength for supporting the windshield or glass, the welders add an extra layer of material by adding a bead of urethane resin onto the diagonal surface.

Vehicle body panels made from z-shaped pinch welds aren’t typically subject to any wear and tear. When comparing them to the welds on the car’s underside, these are superior—jacking up cars in random spots damages welds at the vehicle’s base.

If you want to be sure that the under-the-belly pinch welds won’t fail when lifting your vehicle, use the recommended jack points provided by the manufacturer.


Where Is Pinch Welding Commonly Used?

Automotive assembly

The pinch weld, also called butt joint, is an assembly technique in which two fitting halves are screwed or otherwise made to fit tightly together. A pinch weld seam separates the metal or composite panels to show or hide welding. The automotive industry uses this technique commonly during assembly.

In a car, a pinch weld involves welding the outer frame of the vehicle to the inner body. Pinch welds form seams wherea metal sheet overlaps and sandwiches – or pinches – a layer of a softer but more rigid sheet, typically PVC.The pinch weld is an essential part of making up a car door which locks by pressing into it from either side to help keep the shape and structure of the car door.

 

Placing your jack

Companies that make pinch welds place a small mark on the weld to help you locate the vital part of your pinch weld. You use this as a guide on where to place your scissor jack. In instances where the mark is present, you can set the jack on either side of the pinch weld, depending on the vehicle’s material.

This article will cover the advantages and disadvantages of using pinch welds and why pinch welds may not be suitable for all jobs.


What Are The Pro’s and Con’s of Utilizing A Pinch Weld?

Pinch welds are a type of welding to attach different objects. Welds come in many forms – butt-welding, bevelled-welding, and partial fusion. Pinch welds can be a great way to fix common issues with nuts and bolts coming loose, but they also have disadvantages.

Pros
  • This welding method proves much cheaper, easier, and more efficient than using nuts or bolts to clamp different parts of the vehicle’s structure.

  • Pinch welds make a tight and butt-joint connection, also known as spot welding. You can use themto fasten two or more pieces together temporarily or permanently.

  • They provide a spot to place jacks beneath the car. This function is essential during car maintenance and repair.

  • For mild damage, for example, dents, rust, and breakage, you can repair the pinch welds. Severe damage is,however, irreparable.

  • Pinch welds hold sheet metal together. These are especially useful when heavy items require support from sheet metal.

Cons
  • Automotive manufacturers traditionally use pinch welds to joina passenger’s compartment frames, doors, and fenders. Achieving a solid and reliable steel joint is challenging because steel does not have enough elongation to form a tight joint.

  • It needs a larger oven and has extensive production restrictions. Sometimes, you may require to have it done by a company on your behalf.

  • You cannot use it in many applications with different metal types. It is best when using steel.

  • Depending on where you need to apply a pinch-weld,some areas have difficult welding angles.

  • Pinch weld defects can cause many problems, from leaking fuel tanks to cracked frames. However, even if a pinch weld doesn’t show a sign of being defective, it can still have issues that affect vehicular performance.

 

 


Common issues with Pinch Welds

Corrosion from rust

To repair rust damage on the pinch weld, follow the steps for improving rust anywhere else on the vehicle. You first need to remove any rusty metal from the car. If you want to remove rust from metal, you can either use small tools or cutters to remove the rusty spots altogether.

If you don’t take care of rusty parts, they may cause damage to the whole vehicle, and even new parts could be affected by rust if not taken care of properly. Once you finish cleaning up the rust, it’s time to reinforce the damaged part by installing new metal plates.

Use appropriate metal plates for your car, with the proper thickness, to ensure they fit together nicely.To provide suitable welding, you’ll need to carefully align the two pieces of steel plate together before performing the pinching weld. If necessary, you may want to repeat the pinching weld after completing the first one.

Once everything has been welded together and reinforced, you can prime and then paint.

Dents

Pinch welds often develop dents. If you place the jack wrongly, you may end up having to fix something else, the pinch weld.  It would be best to determine whether there has been any breakage.

If there isn’t any damage, realign the pinch weld to its usual angle. It’s easy if you use hammers and a locking plier. Once you’ve cleaned up everything, you’ll be able to see the scrapes and scratches.

Proceed to clean up any scraps and pieces of bare metal sticking out using a scrapper. Then, use a brush to apply a coat of primer and a layer of paint.

Breakages

If there’s any damage or one side is breaking away from another, you need to repair the pinch weld right away.  If one part detaches from the other, there will be a gap between them.Identify the widest gaps and pinch the two sides together. Use locking pliers or a vice clamp.

You can also use some hammering to align them properly again. Finish by rewelding to keep the pinch tightly shut.You may need to reinforce it if you think it is necessary. Once you’re finished welding everything back together, the last step is priming and painting it, so it looks good again.

There may be some damage that you cannotfix at all. If the damage is so severe that reinforcement or welding won’t help, then you may need to replace the pinch weld entirely.


How to prevent your pinch welds from damage

Pinch welding damage most often occurs from improper use. You must jack up your car from the correct spot so that the pinching weld under your vehicle won’t bend or break. Pinch welding allows for a lot of flexibility when building things out of metal. Unfortunately, there is always a limit – and that includes your pinch weld.

You might not think that a slight bend in the pinch welding would cause any damage to your vehicle, but you’d be mistaken if you thought so. An L-shaped pinch weld underneath most cars keeps everything structurally strong. If it breaks down, water might collect inside your vehicle, causing rust, and that could create even more significant issues.

Bending in the L-shape pinch weld makes your car structurally unsound and not safe to drive. It may not be advisable, but if you jack up your vehicle from the pinch weld just once or twice, there won’t be any damage done. The L-shaped pinch weld beneath your car takes the most damage, especially from impact.

Don’t jack directly from the pinch weld

The best way to prevent any damage is to avoid jacking from the pinch weld. You need to know where these jack points are to use them to lift your vehicle. This option is the best. You can consult your manual to see if you can put the jackstands under the front crossmember as a jacking point.

Use a jack pad

This step to distribute vehicle weight evenly is easy. If you don’t have a jack pad, it would be best to have some wood blocks or a thick piece of rubber. You can place them between the pinch weld and the jack; that way, the weight will be better distributed instead of directly hitting one spot of the car.

Use a suitable U-channel jackstand

Place this U-channel jackstand perpendicular to the pinch weld to rest down in the jackstand. This jack stand may still slightly indent your pinch welds if the car is not balanced. Ensure the U-channels are shallow enough or consult your manual.

The pinch weld rubber seal

Pinchweld rubber seals are common in the automotive industry. They’re able to offer excellent water resistance, sound isolation, dust protection, anti-freezing properties, shock absorption, keeping warm, and energy saving.

These rubber seals create a clean trim for pinch-weld edges. They are dependable, especially in keeping off the rust and ensuring the pinch welds last long. To protect you from getting hurt, they also cover sharp ends of pinch welds.

Pinch welds add strength to structures. These welds are formed under high voltageusing two electrodes to pinch themetal sheets together. Follow the manufacturer’s instructions to give your pinch-weld a long life.