This is one of the preferred methods I use for positioning the spindle centrally over the work piece. This is very accurate way, quick to do and with the visual aid of the clock ensures you are in the correct position. (Even if in the video it doesn’t look like it Trouble holding the camera, talking and trying to set the machine set at the same time. lol)
Centralising the milling machine spindle over the centre line of an indexing/dividing head can be difficult if you have not had to do it before. I hope this video will help to improve your set up of this type of work in the milling machine.
This method works also in a machine vice by clocking either jaw to find the central position. Also, any shape material round, flat, square, across the flats of hexagon etc. can also be positioned centrally using this method.
Sorry about the video. Next time I have to do this setup, I will make improvements to the poor camera work, but from this video, you will get the idea.
The Home Engineer