First of all, let's talk about the cross-sectional circle. Because it needs at least 3 points to form a circle, it is generally better to evenly take 6 or 8 points for the cross-sectional circle, depending on the diameter of the cross-sectional circle. If the diameter is large, you can take more points appropriately. On the contrary, take fewer points, but it is best not to be less than 4 points.

Secondly, there is no specific regulation on how many cross-sectional circles to determine the axis. First, at least two cross-sectional circles are required when building. Generally, the number of cross-sectional circles is better than or equal to 3, and the depth of probe penetration into the hole to be measured depends on the situation. Whether there are chamfers, burrs (thorns) on the end face of the hole, if there are, it should be properly extended to avoid picking inappropriate points. The maximum amount you can reach in depends on how long the extension rod is added to your machine and the effective measuring stroke of the measuring needle. Anyway, it depends on the size of the sample and the depth of the hole, and there is no quantitative standard.