the effective cutting diameter of the attached cutting blades 20 when driven circularly in respect of the diameter of a manhole 23 to be removed as seen graphically in fig8 of the drawings and will be described in greater detail hereinafter referring now to fig1 3 4 and 5 of the drawings a locking alignment assembly 24 is provided on a main support shaft 25 in spaced vertical relation to the main support frame disks 11 and 12 for engagement within the interior i of the manhole 23 to be removed the locking and alignment assembly 24 has a pair of circular mounting plates 26 and 27 with multiple extendable cam elements 28 a 28 b 28 c and 28 d pivotally secured therebetween the upper mounting plate 26 best seen in fig3 of the drawings has a central aperture with an upstanding transfer collar 29 thereabout and a series of arcuate cam adjustment slots 30 a 30 b 30 c and 30 d therein the cam elements 28 a 28 b and 28 c are pivotally secured to the lower plate 27 via pivot attachment pins 31 best seen in fig4 of the drawings adjustment deployment guide bolt assemblies 32 extend from each of the cam elements 28 and are slidably disposed within the corresponding adjustment slots 30 a 30 b 30 c and 30 d as hereinbefore described the upper mounting plate 26 has contoured activation access notches 33 a and 33.