Today was the first time I have ever used the Light Vertical with the head tilted. Amongst one of the job lots of inserts that I bought some time ago was a box with 8 Sandvik round turning inserts, 20mm diameter. I had a damaged 20mm parting off tool with a 6mm thread in the clamp end and it was to be modified to hold the round inserts. Sitting the tool on the rotary table with the 6mm hole centralised, a pocket was milled to match the diameter of the base of the insert, 18.42mm. I used a 16mm solid carbide end mill to mill the pocket to depth and then moved the X axis 0.576mm and rotated the table to get the base diameter. The insert sides are 7 degrees so the mill head was tilted that ammount to make the pocket fit the insert exactly. After tilting the head and setting the lowest edge of the end mill about 0.5mm above the pocket base, I noticed something strange, as if the head had moved out on the Y axis by about 1mm. The cutter was no longed centralised in the mouth of the pocket. The only way to correct this was by eye, I still do not know what had happened, the degrees on the head part of the ram were still in contact with the face with the lining up line. However, the insert fits perfectly in the socket, that was the main requirement.

I have had a good look at everything and have come to the conclusion that I must have been fooled by an optical illusion, Mike agrees with that conclusion. The job has the pocket just off centre as it is a destroyed parting off tool being repurposed and after careful inspection, there is no way that the Y axis could have moved. I have taken a picture of the tool and insert which fit together very well.