Why not use a 5mm bar and get rid of a load of chatter?Made a quick video to show how good these are. This is a 2.5mm head, 2mm shaft mini bar cutting silver steel 0.4mm doc. And very blurry, but you can see the swarf. Final hole in video 10.2mm, couple more cuts I cant be bothered to swap tool. It will be 11.95mm.