There are many kinds of pencils on the market. There are thousands of kinds of pencils, lead, water-soluble pencils, soft pencils, etc. The wood of each pencil is different, and the pencil lead is different. The pencil lead is thick and thin, and the eccentricity may occur in the manufacturing process. It is impossible for any pencil to make the lead core absolutely on the central axis, because the upper and lower parts of the pencil are produced separately, and finally glued together with glue. The error is very normal.