Welcome to the forum, Lars. Good question. I had a very busy schedule when my T4 arrived. I didn't have the time to sharpen with it, only sit it on my bench next to my T7. That turned out to be a very good learning experience. The end sections of both shafts are identical, as is the 12mm diameter. The only difference is the length within the frame. In fact, if you remove the water trough on the T4, an SG-250 fits on the shaft and can be tightened. The 10mm width difference is only at the edge of the wheels. The indented portion of the larger wheel makes the diameter at the bore almost identical. The length of the threads easily compensates for the tiny difference in wheel thickness.
The vertical distance is the same.
Ken
The vertical distance is the same.
Ken