The machine head shot embodies a couple pretty classic "tricks:"
forced foreground; making something that otherwise not be in the pic part of the very front of it...the out of focus worm drive gear crammed in there...nice.
field line magnetism: forcing the viewers eye to follow a line of sight to objects off screen, not necessarily seen...but your brain wishes it could. the line to the back of the pic, and the other way blurred out machine heads...also very nice.
the light is also very nice in that it allows the defects in the driven gear, and the not so very polshed surface of the screw head seem aesthetically pleasing, instead of appearing as faults. ambient light tho, right?
well done.