can exhibit a drop when wear of the cutting element matrix progresses to wear pads within the matrix other wear indicators can also be built into the cutting element matrix progression of wear down to the indicator can be directly measured at the well surface or relayed to the surface via a downhole communication system application_number US 89097707 A description as shown in fig1 through 3 a prior art mill m is lowered through a casing c into contact with a downhole structure to be milled away such as a tubular element t the typical mill m would have a fluid path fp for drilling or milling fluid and the fluid would be conducted to the working surface of the working profile wp of the mill m via fluid nozzles as known in the art which are only partially shown here the mill m is typically rotated in order to mill away the tubular element t with the working profile wp the working profile wp can be a matrix of cutting elements formed on the lower face of the mill m which is in this case represented as an end mill or junk mill for purposes of the present invention the tool could also be a rotary shoe any kind of cutter or even a drill bit similarly the working profile could be any kind of profile mounted or formed on the tool for purposes of performing work on any kind of downhole structure including an earth formation as seen in fig2 and 3 as the mill m is rotated it will mill away a portion of the tubular element t but at the same time the tubular element t will wear a groove g through the cutting element matrix which constitutes the.