How to make a perfect bend in a corner or profile pipe by trimming without bending

Trying to bend metal without a bending machine usually ends in failure. In the absence of such equipment, you simply need to trim the product at the bend and then weld it to avoid creasing or folds. This takes longer than bending, but the result is guaranteed to be of better quality, especially if you do everything correctly in compliance with the calculated proportions.

What you will need:

cardboard;
square;
compass;
marker;
scissors;
Bulgarian;
welding;
vice.

The process of making the correct bend

Let's first consider the technology of marking and trimming using the example of a corner. You need to cut a circle with a diameter of 150 mm from cardboard.

It needs to be divided into 4 equal sectors. One of them needs to be cut with scissors.

The circumference of the sector is measured on a ruler; it is 120 mm.

Next you need to measure the width of the corner. This distance is marked along the smooth edge of the cut out cardboard pattern on the side of the circle.

The compass is moved so that the needle is at the corner of the sector, and the stylus hits the marked point.In this position, you need to draw a circle on the template. It is cut along the resulting line.

Next, you need to measure the circumference of the template after cutting. In this case, it went from 120 mm to 80 mm. The wider the metal for bending, the shorter the length of the second circle will be.

Now the labels are calculated. To do this, the 80 mm obtained after trimming is subtracted from the original circumference of 120 mm. The final difference is divided by 5. In this particular case, 40/5 = 8 mm. This is the label setting step.

On the inside of the future bend of the corner you need to put 10 marks, starting from the calculated step. Zero is done at the beginning. The rest in this example are indented from it at a distance of 16, 24, 36, 44, 56, 64, 76, 84, 96, 104 mm. It's simple. The first mark after the zero mark is always indented by 2 steps. Next you need to alternate 1 and 1.5 steps.

You need to put 5 marks on the outside of the bend. They are made with an indentation from the origin equal to half the difference in the length of the calculated circles. In this example, it was 40 mm, that is, the pitch will be 20 mm.

From the inner 5 marks you need to draw 2 lines to the other side to the nearest side points. Then the resulting wedges are cut out.

After this, the corner is bent until the cutouts meet. The result will be an angle of 90 degrees.

All that remains is to weld the gaps and sand the seams.

You can bend a profile pipe in the same way. The only difference is that the wedges for the cutout need to be drawn on the opposite wall.

After bending, the gaps are also welded and ground. Having remembered these calculations, you will be able to ideally bend corners and profile pipes of any width.