Grinding an ER collet chuck

How turning and grinding an ER collet chuck . Although the result is not what I was hoping for, in the video I try to show the correct procedure to finish the conical hole of the chuck.
Independently of the attack you use behind the collet chuck (cylindrical, iso 30-40-50, MHD, MT2-3....., CAPTO etc.) the procedure for finishing the cone is always the same.
The basic concept of this processing is to use the centers (around which the shank has been built) and to support one of these diameters (turned at the same time) on the fixed steady rest to perform the grinding.
On the professional grinding machines the millesimal comparator, installed on the finished cone, DOES NOT move.
This system is great also for the holes grinding and whatever requires more precision.
A grinding, made with a maximum precision self centering chuck and performed by centering the piece, will never give the same result if not locally, because maintaining the concentricity along the axis of the workpiece is very very difficult.