Welding joints: what to know for your DIY projects

That’s right: it’s time to move from the basic level of welding knowledge to an intermediate level. Let’s start by adding some more technical knowledge, never forgetting that we are not professional welders but DIY enthusiasts!

So, let’s start from weld joints, that is the way we can weld together two metal workpieces. In this article we will look at four of them: these are the most common ones you will come across in your projects with your DIY welding machine. Pay attention: they are in order of difficulty!

Corner joint
This is the most classic of joints. You make it when you join two workpieces at 90°, as you see in this figure.

As usual, before you start we recommend that you follow the No. 1 rule of welding: clean the workpieces to be welded. Residues from previous processes such as cutting oil or scale from the manufacturing process do not get along well with welding. And so does any rust (remember Martina’s video where she cleans the horseshoes of the bottle holder?).

Once everything is clean, make sure that the sheet metal has sharp edges vertically, so you will be more precise in positioning.
Reduce the distance between the workpieces as much as possible to make your welding work easier and avoid welding defects that could compromise the weld itself.
If possible, weld both sides of the joint. Think of the two joined workpieces as a hinge or a door: double welding will prevent it from breaking.
Don’t be fooled by how easy it is to make a corner joint and try to weld as we show in this figure.

Lap joint
You make a lap joint when you need to make a bar or pipe longer by putting a metal ‘patch’ between the two parts. We are still in the group of easy weld joints, since it is easy to keep the two workpieces straight together and the single piece once finished.

Don’t forget rule No. 1 and try to bring the workpieces as close together as possible, perhaps with the help of a clamp.
The weld should look like the one you see in the picture below. And watch out for the sharp edges! Maybe after welding, round them off with a grinding wheel.

Outside corner joint
This is the joint you get if you want to make a vase, a tank, or a metal box…

We don’t have to remind you of rule No. 1, do we?

But watch out: an outside corner joint is not one of the easiest because the workpieces don’t fit in the position you want. Use angle brackets held with clamps or magnetic positioners.
The secret here is to apply many spots to hold the workpieces in place before starting the actual welding.
If the object you are creating is supposed to hold liquids, pay attention to the edges. Welding should never start or finish on them. Start welding a little before or stop little beyond the edge. If you have gone a bit too far with the welding, don’t worry: fix it with an extra bit of grinding.
Another case: if you stopped and want to start again from the same point, you can avoid overlapping the welds as follows: make a groove with the grinding wheel in the last section and start again a little before the already executed section. At the end of the second section, give it a grind.
If you can assemble everything as shown in the picture and manage to melt the inner sides together, seal is assured. In short, you can brag to your friends that you make great welded joints!

Butt joint
Making this joint is like butting heads! But you can do it! The two workpieces must withstand opposing forces, as you see in this figure.

You should avoid this type of weld joint. Just look at large civil engineering works such as bridges and sheds, or (if you are lazy) the gazebo in your garden. You never come across this type of weld: you will always notice plates welded at 90° and held together with bolts: no messing around here.
No, no one is saying your DIY project is a joke. Otherwise we wouldn’t have proposed it to you, right? If your project has butt weld, try to make them where there is less stress.
Then, try not to grind the surface with the grinding disc: leave the weld mound that has formed (in jargon, the weld bead). If, on the other hand, you absolutely need to even the surface, then add reinforcement plates.
Finally, try to fuse the entire thickness: if you succeed, you will have a full penetration weld. This means that the weld should look like the one in the picture below. And it also means that you can congratulate yourself on the excellent butt joint you made!

Well, now you know the different types of weld joints and you can go to work on any project! Without any fear and always following the safety rules. And rule No. 1 of course!