hydraulic swivel head

hydraulic swivel head

[hi′drȯ·lik ′swiv·əl ‚hed]
(mechanical engineering)
In a drill machine, a swivel head equipped with hydraulically actuated cylinders and pistons to exert pressure on and move the drill rod string longitudinally.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.