How to draw a circle? For example. Pipes.

Draw the main view ① according to the size;

2. Draw a plan ② according to the size;

3. Divide the circumference in the top view into 12 equal parts, and connect the points with line segments according to Figure ③, which are respectively equal to line 1, line 2, line 3 and line 4;

4. Make a line segment equal to line 1, make a vertical line equal to the height of front view ①, perpendicular to line 1 at point A, and connect point B and point C equal to line segment1; The line segment AD from point A is equal to line segment 2, and the line segment 2 connecting point D to point C is equal; AF is equal to line 3, and the connection point f to point c is equal to line segment 3; AE is equal to line 4, and line e points to point C.

5. Make an expansion diagram ⑤