head section

[frankie_goes_to_hollywood]

головной секции ?

If this same cone is attached to a head section as a member of a bit, the cone will be forced to rotate about the bit centerline. A cone with its apex coinciding with the bit centerline will have a true rolling action. The center of cone rotation and the center of bit rotation are the same.

[Катерина С]

Я бы написала "к верхней части".