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How to Get Stronger Welds With Thick Metal



Kevin is clamping a piece of 1/2" steel plate to his work table. He was just about to chamfer the edge so he could cut the rectangular chunk of metal in half, then weld it back together to make a square.

Chamfering is used when you are welding a thicker piece of metal - in Kevin's shop, that's anything over 1/8". When you chamfer, you grind away the edges of the metal to create a "V" in your joint so you can fill it more thoroughly for better penetration.

Using a piece of 1/2" steel plate as an example, Kevin shows how you start 1/4" from the edge of the top of the metal - roughly half the thickness of the metal you are welding - then measure down into where the weld will be a little less than 1/4" - again, roughly half the width of the metal itself - and grind it off. Then you do the same thing on the bottom, which leaves a flat "tab" that matches up to a similar flat spot and bevel, or chamfer, on the other steel plate you are welding to. Before you begin welding, you separate the two pieces of metal about 1/8" or 1/16" so that, when you weld it, you get penetration down between the plates. Now you're ready to weld. You weld the open areas with your root, or bottom, pass, then fill with as many welds as you need, ending with a cap pass. Then you do the bottom side of the metal the same way.

If you don't have access to both sides of the piece to do a double chamfer, however, you can grind a deeper angle on your top side and leave your flat spot where the two pieces butt together at the bottom of the weld to create a single chamfer.

When you chamfer, you want to grind both pieces of metal so the area you are welding looks like a valley.

If you're creating a double chamfer, or bevel, be careful not to have the area where the two pieces of metal you are welding butt together come to a point. If you do, when you start welding, you'll blow right through the metal as soon as you start welding.

Next, Kevin chamfers the piece of 1/2" steel, first grinding across the top, then grinding across the bottom, and finally giving the flat edge, or "tab," where the two pieces of metal will butt together a quick lick with the angle grinder.

Kevin shows how the top angle is about a third, the flat section about a third, and the bottom angle about a third of the metal edge. He laughs about his measuring, but says this gives you an idea of how it works.

The goal of chamfering is to get better penetration on thicker metal without having to turn up the amperage or voltage on whatever welder you are using to try to power through it. This way you can get good penetration at a lower voltage and not overheat the metal. It's just good practice and the way that works for him.

Kevin used a 7" angle grinder with a stone wheel, not a softpad, because he really wanted to cut some metal. He's not worried about how the ground area going to look, because it's all going to get welded over anyway.

He also points out that he uses a dust mask, hearing protection, safety glasses and gloves while grinding, keeping an eye on where the sparks are going.

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