How to draw isometric projection

Construct with a ruler and protractor or compass and ruler coordinate axes for rectangular (trigonalidae) isometric projection. In this kind of axonometric projection, all three axes OX, OY, OZ form between them angles of 120°, while the axis OZ is the vertical direction.

For simplicity, draw the isometric projection without distortion on the axes, so as is customary isometric distortion to equate to unity. By the way, the word "isometric" in Greek means "equal size". In fact, when displaying a three-dimensional object on a plane the ratio of the length of any projected line segment parallel to coordinate axis, to the valid length of this part is the same for all three axes of 0.82. Therefore, the linear dimensions of the object in the isometric (when the adopted distortion ratio) increased to 1.22 times. The image is correct.

Start to project the object on a perspective plane with its top face. Measure along axis OZ from the centre of intersection of the axes of the coordinate height of the part. Fine with axis lines X and Y through that point. The same point put half of the cut part length on one axis (e.g. the Y axis). Swipe through the point cut the desired size (width of part) parallel to the other axis (OX).

Now along the other axis (OX) set aside the half-width. Through this point guide cut the desired size (length of part) parallel to the first axis (OY). Two drawn line segment must intersect. Extend the remaining part of the upper face.

If this face has a circular opening, draw it out. In the isometric circle is shown as a ellipse, because we look at it at an angle. The dimensions of the axes of this ellipse calculate based on the diameter of the circle. They are equal: a = 1,22 D and b = 0,71 D. If the circle is on a horizontal plane, the axis a of the ellipse is always horizontal, the axis b is vertical. The distance between the points of the ellipse on the X-axis or Y is always equal to the diameter of the circle D.

Draw three corners of the upper edge of the vertical fin equal to the height of the part. Connect edges through their bottom points.

If the figure has a rectangular hole, draw it out. Aside from the center of the rib top face vertical (parallel to Z-axis) cut the desired length. Through the obtained point to draw a segment of the required size parallel to the top face, and hence the x-axis From the extreme points of this segment, draw a vertical rib desired value. Connect them to the bottom. Swipe from the bottom right point of the diamond is drawn the inner edge of the hole, which should be parallel to the y-axis.