I tried cutting a hemispherical void of 0.502" in diameter in a piece of MDF. I used a 1/4" ball mill for the milling. The void looked fine, but when I placed a ball with a diameter of 0.500" in the void it sat noticeably above the equatorial plane of the ball (like the pocket was either too shallow or the sphere-shaped void's diameter was too small. Any thoughts of what went wrong?
Greg