I have had an on going issue with my 1983 Mark V 500. We have a fellow member that has a brand new Mark 7 PowerPro Plus that is dealing with the same issue on his new machine.
The problem stems from what I describe as blade wobble. On my machine when the blade slows you can actually see where the blade does not swing true. It appears to wobble. I just had my headstock completely rebuilt. It has a single bearing quill that was rebuilt. I also bought a new 5/8th arbor. I noticed the blade movement on day one. Knowing the machine was solid I thought I had a bad arbor. I bought a new arbor. I still have what looks like a wobble. We tried several different blades. I still have what looks like a wobble. We put the machine in drillpress mode and installed a brad point bit. It Drilled straight and true. Zero bit walk or knock with a brad point or a forstner drill bit. I gave up. It is what it is.
I have been helping a new member along with his new 7 PP+. He is experiencing the exact issues that I have. Like me he bought a new arbor. Like me he has tried multiple blades. He describes his wobble issue exactly the same as mine. EXACTLY! Our fellow member is genuinely frustrated with what is obvious to the eye. That blade is not true. I could add more words but it would be blah blah blah. I/we are open to any thoughts ideas or criticism on the issue of what appears to be blade wobble. Ideas PLEASE!