how we can to calculate the dgree in the onshape between two circls

I would create a sketch from a plane sectioning the CSK hole and draw a line that connects the two edges of the hole. Then just dimension or measure the angle from that line to a horizontal line.

But fwiw, most CSK holes are 82°. The 100° are reserved for aerospace applications where they want the larger mating surface area.

Try some trig.

r2 is the radius of the larger circle. r1 is the radius of the smaller circle. t is the thickness of the plate. Compute θ from the opposite and adjacent sides of a right triangle. Note that a countersink bit would be sold with an angle of 2θ.

If you made the hole with the OnShape Hole Tool, it will tell you the angle of between the two circles.

In the above screenshot, you would have to find the hypotenuse between the **red and green lines** and then do the trig with that value and either the blue line with inverse tangent or the “min dist” with inverse sine. Blue represents the plate thickness. The red and green lines are trying to represent the difference in circle radii, broken out into x and y components. You save steps by starting with the circle radii rather than the min dist components.