zonal wall 23 i e in the direction away from the working end of the adapter 13 the shank 22 is equipped with an integral reduced cross sectional area portion 18 lastly the extreme end of the shank 22 i e the mounting end terminates in an end wall 24 which again is a spherical segment like the interior end wall 21 of the recess 14 the shank portion 18 can be seen in cross section in fig6 and has the shape of a regular polygon twelve sides are depicted and these are seen to be in spaced relation from the interior wall 20 of the mounting part 11 it will be appreciated that the number of sides in the polygonal shank 18 can be varied in operation the shank 22 of the adapter 13 is introduced into the recess 14 of the mounting part 11 by virtue of the confronting walls 19 and 23 the adapter 13 can be rotated both about longitudinal and transverse axes to a desired attitude in the illustration given movement about transverse axes is of the order of about 6 u00b0 as determimned by the rearward divergence of the frusto conical wall 20 thereafter a thermoplastic material such as epoxy resin in liquid form is introduced into the port 25 see also fig6 so as to fill the generally annular shaped space 26 between the polygonal walls of the shank portion 18 and the frusto conical interior wall 20 i have found it advantageous to condition the steel surface of 22 beforehand through the use of grease vaseline or some other material that will create a film on the.