reference cutterbar 30 is mounted in a disc mower 10 having a support frame 11 connected to the three point hitch mechanism 3 of a tractor t on which the mower 10 is carried in a conventional manner the disc mower 10 receives operative power from the conventional tractor power take off shaft 5 the mower drive mechanism 15 receives the rotational power from shaft 5 and transfers the rotational power to a gearbox 17 which in turn transfers the rotational power to the cutterbar drive mechanism an alternative configuration for the disc cutterbar would be to incorporate the cutterbar in a disc mower conditioner this well known configuration is shown in more detail in u s pat no 5 761 890 which is hereby incorporated herein in its entirety by reference one skilled in the art and knowledgeable about commercial applications of disc cutterbars will readily recognize that there are other specific configurations of cutterbars to which the invention to be disclosed herein will be applicable such skilled individual will also readily recognize that the cutterbar need not necessarily be modular in construction modular cutterbar 30 is formed from alternating cutterhead modules 40 and spacer modules 32 each cutterhead module 40 as best seen in fig1 3 includes a hollow cast housing 41 fig3 having a shape to retain a low profile and to establish an oil reservoir 44 therewithin cutterheads 40 are gear driven and assembled in such a manner as to establish a specific timing relationship between adjacent units more particularly the cutterheads are arranged such that.