the beginner's guide to welding sheet metal

It's normal to feel wary about welding for the first time. You'll be using high heat and powerful equipment, and you'll be permanently altering the sheet metal with no easy way of fixing it if something goes wrong. No wonder you want to be careful!

The good news? With the right approach, safety gear, and equipment, you can create strong, clean welds without any unnecessary risk to yourself.

The Clickmetal team have been working with all sorts of sheet metal for years, so we know exactly what it takes to make a safe and successful weld. Read on for our beginner's guide to welding sheet metal, covering everything from the necessary gear to the step-by-step welding process.

What Equipment You'll Need

Unlike some simpler methods (such as screwing), welding involves using several advanced tools. Here's the equipment you'll need to get started:

Welding Machine

There are two main types of welders used for sheet metal welding: MIG (Metal Inert Gas) welders and TIG (Tungsten Inert Gas) welders.

MIG welders are a popular choice for sheet metal welding due to their ease of use and versatility. They use a continuously fed consumable wire electrode and an inert gas shielding to protect the weld from contamination.

If you're using a MIG welder, you'll also need a gas cylinder filled with a shielding gas, typically a mixture of argon and carbon dioxide. This gas protects the weld from atmospheric contamination and allows for clean, strong welds.

TIG welders use a non-consumable tungsten electrode and an inert gas shielding. They offer more precise control over the weld but require more skill to operate, so we'd recommend using a MIG welder instead for your first welds.

Wire

The type of wire you need depends on the metal you're welding and the thickness of the sheet metal. Match the wire diameter to the sheet metal thickness and be careful to avoid using wires that are too thick, as they can deliver too much heat and cause the sheet metal to warp or melt.

Here are the typical wires you'll need for MIG welding common metals:

  • Aluminium: ER4043 or ER5356 aluminium filler wire.
  • Mild Steel: Solid steel electrode matching the composition of the mild steel being welded (e.g. ER70S-6 or ER70S-3)
  • Stainless Steel: Solid stainless steel electrode that matches the type of stainless steel being welded (e.g. ER308L for 304/304L stainless steel and ER316L for 316/316L stainless steel).

Consumables

  • Shielding Gas: As mentioned earlier, a gas mixture of argon and carbon dioxide is commonly used for MIG welding. When welding sheet metal, avoid using 100% CO2 as it promotes deep penetration and can cause burn-through. Instead, opt for a 75% argon / 25% carbon dioxide mix for better control.
  • Contact Tips: These small components connect the welding wire to the welding gun and should be compatible with the wire diameter you're using.
  • Nozzle and Diffuser: These parts help control the gas flow and direct it properly during MIG welding.

Other Tools

Depending on your project, you might also need additional tools such as clamps, cleaning tools (like a wire brush or grinding wheel), and a welding table. For more detailed information, refer to the manufacturer's recommendations for the specific type of metal and welding process you're using.

How to Protect Yourself

Welding sheet metal exposes you to several hazards, but there are a lot of ways to protect yourself. Here's a breakdown of the key areas to focus on:

Wear Proper Safety Gear

  • Welding Helmet: This is your primary defence. Select a helmet with the appropriate shade rating for your specific welding process. A shade guide is usually located on the helmet itself, or you can consult a welding supply store for recommendations based on your welding technique and materials. Make sure the helmet offers good visibility and a comfortable fit for long work sessions.
  • Respirator: When ventilation isn't enough, wear a respirator with the proper cartridges or filters for the metals you're welding.
  • Welding Gloves and Protective Clothing: Wear heavy-duty welding gloves, a welding jacket, and clothes made from flame-resistant material to protect yourself from sparks, heat, and molten metal.

Practise Good Safety Techniques

  • Welding creates fumes that can be toxic. Always weld outdoors whenever possible to let the fumes dissipate. If welding indoors is unavoidable, use a Local Exhaust Ventilation (LEV) system. This system captures fumes and contaminants at the source, preventing them from spreading throughout the workspace.
  • Keep a fire extinguisher readily accessible in your welding area in case of sparks or ignitable materials nearby.
  • Regularly inspect your welding helmet, respirator, and gloves for signs of wear and tear. Damaged equipment can compromise your safety, replace any faulty components promptly.

Skipping any of these steps can put you at risk of serious injury, so always put safety first. If you're not feeling confident, you may want to practise under the supervision of an experienced welder or seek their advice first.

How to Weld Sheet Metal

Once you've gathered your equipment and made sure you've followed all the safety practices mentioned above, you're ready to start your first weld! This guide focuses on MIG welding, as it's the most beginner-friendly method. Once you're comfortable with the basics, learning other techniques will be much easier.

Before moving onto your actual project, you may want to practise on scrap pieces to get comfortable with the settings and technique. This will let you experiment and find the best settings for your material thickness.

Ready to make some sparks fly? Follow these steps to make your first bead!

1. Prepare the Metal

First things first, you need to get the sheets themselves ready.

Contaminants can hinder a good weld, so clean the weld area thoroughly with a wire brush or grinder to remove any dirt, grease, paint, or rust.

Next, decide on your joint type (butt joint, lap joint, etc.) and prepare the metal edges accordingly. Beveling the edges can be helpful for thicker materials (around 1/8" and above) to achieve better penetration.

2. Set Up the Welding Machine

Let's get your welder set up! The exact steps might vary depending on your machine, so be sure to check your welder's manual for the specifics. Here's a general rundown to get you started:

  • Install the correct size MIG wire according to your machine's recommendations and the thickness of the sheet metal you're welding.
  • Set the gas flow rate according to your manual (typically 20-25 cubic feet per hour). The gas flow rate helps shield the weld pool from contamination and ensures a clean weld.
  • Start with low voltage and wire feed speed settings. A good starting point is referencing a welding chart for recommended settings based on your material thickness, then fine-tuning as needed.

3. Position the Sheet Metal

Position the pieces to be welded and secure them with clamps or tack welds if needed. Clamps keep the pieces aligned during welding, while tack welds create temporary connection points for lap joints or to prevent warping on longer seams.

4. Load the MIG Gun

Load the MIG gun with your chosen wire and make sure it feeds smoothly into the device. Any stuttering or erratic wire feeding can cause inconsistencies in the weld.

5. Begin the Weld

Turn on the power switch on the welding machine and hold the gun to the metal. Next, you should:

  • Maintain a very short arc length (around 1/16") between the contact tip and the metal, as a long arc length increases heat input and can melt through thin sheet metal.
  • Use a "stitch welding" technique. Make short, quick welds (about 1/2" long) with a slight pause (1-2 seconds) in between each weld to allow the metal to cool down. This prevents overheating and minimises the risk of burn-through.
  • Keep the travel angle between the torch and the metal at 10-15 degrees, pushing the torch slightly ahead of the weld pool. This angle focuses the heat on the leading edge, allowing for better penetration and creating a good bead profile.
  • Focus on creating a consistent bead profile without excessive heat. A good weld bead should be slightly crowned (raised in the centre) and have a smooth, regular appearance.
  • Let the welded area cool down completely between weld passes. This prevents overheating and potential cracking in the weld.

6. Finish Up

Once you've finished welding, inspect the joint for quality. Look for cracks, porosity (air pockets trapped in the weld), or incomplete fusion. You can chip away any slag (glassy byproduct of the welding process) with a chipping hammer and clean the area with a wire brush. You can also grind the weld seam for a smoother finish, but be careful not to overheat the thin metal. Excessive grinding can create notches or gouges that can weaken the joint.

Don't worry if you haven't got it perfect the first time - welding is a specialised technique that can take years to master. Just keep practising, and you'll see yourself getting better with every arc you strike.

Level Up Your Welding With Precision-Cut Sheet Metal From Clickmetal

Ready to get started on your next welding project? Get the exact sheets you need with Clickmetal! We offer a wide variety of high-quality sheet metal in different thicknesses, all cut to your exact measurements. Choose from:

All our sheet metal is manufactured in-house with top-of-the-line equipment, so you can be confident you're getting top quality with every piece you order. We also process most orders within 3-5 working days, followed by next-day delivery through a reliable courier service, so you can get started ASAP.

Don't waste time hunting for the right sheet metal. Browse our vast selection online and find the perfect fit for your project today!