by the drawings of fig7 a 7d the taper of the second portion b is 0 04 mm mm the files of fig7 a 7d are discussed hereinabove these and the remaining files of fig8 10 are provided with a radiussed surface in which the change of taper occurs gradually with distance from the tip from the taper of the first portion to the taper of the second portion this is shown by the curve in the region c of fig7 10 fig8 a 8d schematically represent still another pair of sets of files in accordance with the invention fig8 a 8d show files 81 82 83 and 84 in a multi tapered configuration in each of the files 81 84 there is a first portion u03b1 adjacent the tip 90 and a second portion u03b2 remote from the tip extending to the shank in these sets of files each of the first portions is a different length from those of the other first portions being shortest for the file 81 which has the greatest taper of the first portion u03b1 0 12 and increasing successively for files 82 83 and 84 as the taper of the first portion diminishes beginning at 0 10 for file 82 and ending with 0 06 for file 84 as with the sets of files of fig7 a 7d one set of files 81 84 has a taper of 0 02 mm mm for the second portion u03b2 whereas another set has a taper of 0 04 mm mm for the second portion u03b2 fig9 a 9d schematically represent another set of four multi tapered files 91 92 93 and 94 in accordance with the present invention each of the files is shown with a first portion a.