This was a garden tree here at my place , chosen for the excellent graft 15 years ago .I didn’t plan to use it as a Bonsai until a borer attack 2 years ago . Most of my Maples were effected and have been removed as i was unable to control the borers . It was removed and potted up hoping to salvage the trunk .With a good show of leaves last season i would have assumed it had  put out a good root spread . I did attach a few maple whips as thread graft for new roots , unfortunately the failed to fuse to the old root base and the trunk didn’t produce many roots at all . Not one to give up i decided to inarch 24 T rident Maple whips around the base of the trunk just above the old base . Using an Angle grinder with a tungsten saw blade attached i cut 2 dozen 2mm slits around the base at even intervals and inserted the 3mm Trident whips into position .As the seedlings were inserted the fine bark on the whips was disturbed , this i hope will aid the fusing together of whip and trunk .With all the whips attached i simply wound several layers of grafting tape around and over the area where fusing is required then potted the tree up into its original pot .This will grow on for another season and then i may have suitable new root mass to work with .Nothing ventured nothing gained .Cheers Alpineart