Mike, the big issue with Celtic Cross' and actually for many other types of segmentation is the reference points for each cut made.
Traditionally, the most common way is to attempt to keep the blanks as perfectly square as possible so that each side that is used as a reference is as similar to the next as possible. So to make a 'cross' you have 4 different reference points plus the end of the blank. Then you add a 5th point by trying to drill exactly in the middle of your first 4 points.
With a little ingenuity you can make all your cuts from the same reference point.
Here are some old pics that show a little indexing gadget that I knocked up that is used on a compound ( x-y ) table.
The blanks all rotate about their centres.
The only difference between the crosses and the feathers, is the depth of the cut.
Of course it is perfectly possible to do very accurate cuts on a table saw and then drill down the middle, but it has to be absolutely spot on or it looks bad.
For me, doing it all from the middle is far easier. :wink: