- Nov 16, 2012
A couple questions.
Why didn't you turn the MT first and do your boring with the piece held in the H.S. MT?
Also, would it be "better" to grind your 30° point after completion? I wouldn't know how you'd hold the MT though unless you did it in the H.S.
These questions are mute though as yours turned out perfect but curious to your answer.
If I cut the taper early on, I would not want to risk doing that many boring and facing operations on a piece only held in the spindle with a Morse adapter. The headstock has a native MT5 taper so, a MT5 to MT3 adapter would be needed. That arrangement works fine to hold a dead center but, it would not hold a workpiece -especially if any kind of side pressure is applied. I can almost guarantee that would have a very bad outcome.
Immediately after the part was heat treated, it was cut the entire length and the big and small outer diameters were made perfectly straight and concentric. If the taper were cut early on, I would limit the options for holding the piece and also reduce (by over 50%) my ability to indicate the part over it's whole length. You can never indicate a part in one place and assume the entire length spins true. Since the small diameter was under 1-1/16", a 5C collet chuck was the natural choice to hold it. I'll add to that and mention that my 5C collet chuck is as close to perfect as is humanly possible.
The take-away here is that you can only use the headstock taper to spin between centers whereby the tailstock pressure keeps the part held firmly. If the tailstock pressure is compromised, the two interfaces in the headstock (headstock itself and the adapter) will give way. That's almost a foregone conclusion.