Before we weld any metal structure, we first cut the required blanks to size. The more accurate these blanks are, the easier it will be to assemble and weld any structure. But there are 2 tricks that beginners often get wrong with. Let's take a closer look at everything.
We have a whip of a profile pipe 2727 mm long. Let's say you want to cut 5 pieces of exactly 500 mm long from this pipe. The more precisely we cut these 5 pieces, the volume will be easier further. See what mistakes beginners make.
From one end of the pipe, we set aside the dimensions and draw lines at the numbers 500 mm, 1000 mm, 1500 mm, and so on.
I took a grinder and, focusing on the line, began to cut. The disc goes close to the line-close, but does not find it. And so we cut off all 5 pieces that we get. The first piece will be exactly 500 mm, but all the others will be smaller. Why did it happen? We did not take into account that the disc eats up the metal to its thickness when cutting. Starting from the second workpiece, the dimensions will be less than 500 mm. And then how to mark correctly? It's simple, look.
Only 2 pieces need to be cut from the whole pipe at a time. So we make 2 markings from opposite ends. But here, too, there is one rule.
My disc on the grinder is on the left side of the gearbox. This means that when the tool is running, the disc will go to the right of the marking line. What does this mean and how to take it into account.
When marking the desired piece of the workpiece from the left end of the professional pipe, we set aside exactly 500 mm. We draw a line and saw with a disc close to this line. At the exit, we get a workpiece of exactly 500 mm.
And from the right end of the pipe, we will postpone a slightly larger size. You just need to add the very thickness of the disc. Let the disc be 1.5 mm thick. So we set aside the size of 501.5 mm. And we also go with a disk close to this line. We get the workpiece as needed, 500 mm.
These 2 rules should always be applied if you want your workpieces to be exactly the same dimensions in millimeters that are needed for the design. Then you don't have to weld large gaps.
This is how not only profile pipes are cut, but also corners, channels, and any other materials.