How to make concentric circles on the construction site

In the plan view, according to the geometric relationship of the cylinder, a square is made on the outside of the column, which is parallel to the longitudinal and transverse directions of the column center. The side length of this square is the diameter of the concentric circle of the cylinder, which is called the circumscribed quadrilateral of the concentric circle, and the midpoint of each side of the square is also called the tangent point.

For example, suppose the diameter of the field cylinder is 1m, and plan to make a 2m concentric circle.

1, according to the geometric relationship of the plane, calculate the plane size of the two intersecting axes in the center of the cylinder;

2. Place the positions of the two intersecting axes in the center of the cylinder on the horizontal axis and below the central axis of the cylinder 1m respectively, and play a chalk line on the left and right axes to form a square with a side length of 2m;

3. Measure the midpoint of each side of the square with a tape measure;

4. Put two laminated plates on the site ground, align the flat-fell seam, fix a nail in the center of the flat-fell seam, draw a circle on the laminated plates with a carpenter's pencil with a radius of 1m, cut off two semicircles of the laminated plates with scissors, and keep the outer model;

5. Align the circular model with the midpoint of the four sides of the square, and draw lines on the spot to get a concentric circle with the cylinder radius of1m..

In practice, only the midpoint of the four sides of a square is needed to check the cylinder.