Clip out of range data from a plot

I am plotting a 3D graph (using plot3) I am defining my axis([-8,8,2,50,0,20]) With centre as (0,2) I am drawing some semi-circles. If the radius of the circle is >8, the x-axis is expanded by itself and the limit defined (-8,8) doesn't hold. I want to clip that part of the semi-circle which is beyond -8 to 8 and want only an arc to remain in the graph if radius>8

Any help will be really appreciated

Answer 1

[Walter Roberson]

Also give the command

axis manual