spindle 208 it is formed with a hyperboloid sleeve portion 208c having a ring 208d supporting at least one insert tool 210 the tool 210 is received in a pocket in the rim 208d and would function as the tool 173 described in connection with the embodiment of fig9 and 10 a mechanism similar to that shown for the embodiment of fig9 and 10 could be employed to move the tool 210 radially with respect to the spindle the elongated configuration of the spindle unit 200 adapts it to boring deeper holes as might be required in connection with internal combustion engine cylinder walls shown in dashed lines in fig1 is the outline of a bored cylinder wall 212 it is also noted that hyperboloid sleeve 208c has a configuration that permits use of a smaller diameter bearing 204 than the bearing employed in the embodiment of fig9 and 10 it is also contemplated that the spindle unit 165 or 200 may employ multiple insert tools mounted around the periphery of the spindle to be used for boring and milling with such multiple inserts there would be no use of the wall flexing feature the embodiment of fig9 and 11 differ from the other embodiments in the manner in which the tool is supported by the spindle and the manner in which the spindle.