The Dado arbor is longer than the saw arbor. This extra length causes the interference problem if the table needs to be moved too far to the left in order to center the blade or "accessory" in the table insert.
By locating the blade or "accessory" further out on the arbor shaft with the wider spacer(s) the table insert can be centered over the "accessory" without the interference problem.
I should have noted that the photo is of a 510/520 table and the current production molder/dado arbor (p/n 505506). The saw blade is installed against the narrow spacer.
This post is very enlightening and should be saved for the next time this subject comes up.
Although, it has been shown that when push comes to shove, the dado/molder arbor can be used to hold a saw blade, it would be a better choice not to do this - if there is a choice! Too many variables that could compromise safety, and many of them serve to extend the quill putting more sideways pressure on the quill bearings!
Good Thread - guys!:D
Octogenarian's have an earned right to be a curmudgeon.
Chuck in Lancaster, CA
Thanks Dennis - "I see said the blind man"......... This may explain why on at least three of the 510/520 machines I have purchased, they came with the tiebar shield removed.
I have one of the old 5/8" universal arbors and it does not interfere on my 520.
