main cutting head 50 more particularly the drum extension portion 208 includes a toroidal hydraulic cylinder for selectively extending and retracting the drum extension portion 208 the drum extension portion 208 has an axial inner end adjacent the main cutting head 50 and an axial outer end and the drum extension portion 208 includes an inner end structure 212 attached to the main cutting head 50 the drum extension portion 208 also includes an outer cylinder 216 attached to the inner end structure 212 and an inner cylinder 220 attached to the inner end structure 212 the inner cylinder 220 also has an outer surface 224 and the inner cylinder 220 is coaxial with and received within but spaced apart from the outer cylinder 216 the inner cylinder 220 is also adapted to be connected not shown as is cylinder 66 in fig2 and 3 to an outer cutter head 60 the drum extension portion 208 also includes an extendable cylinder 228 and an end cap 230 the extendable cylinder 228 has an inner annular enlarged end 232 and a portion of the extendable cylinder 228 is received between the inner cylinder 220 and the outer cylinder 216 the enlarged end.