Here is my method of truing up an arbor that’s not really bad, but not quite where it needs to be either.
For a little background I bought this saw off of a guy that buys equipment from school auctions. This ‘93 Unisaw was at a vo-tech local to me. It’s actually in pretty good shape, but has seen A LOT of use. I took the top off of it to better clean it and figure out why the blade elevation was so stiff. Turns out it just needed cleaned and lubed as the gear racks had very little discernable wear. They looked basically new when cleaned up!
Note that I took these pics when I was almost finished, but hopefully you can get the gist of the process.
First off mark the high and low spots. For this I usually put a mark with a sharpie pen at the lowest spot. At the highest spot I’ll put two marks. Then I colored edge the outside of the arbor between those two points.
If you notice, I don’t “color” all the way up to the mark at the lowest point, because I obviously dont want to remove material from that place since it is the lowest, so I stop a bit short of it. In the above pics I’m NOT stoning the area that isn’t colored, I mark the circumference that I want to remove material from.
I used a medium grit Norton india stone using a light oil or mineral spirits. Keep the stone flat on the arbor face and you need a stone with a good flat surface. This stone is about 20 years old and on it’s last legs for anything other than general purpose stuff but it was still good enough, there’s no telling how many parts I’ve used this on on. Go slow and recheck often by wiping it down with a paper shop towel.
This could probably be done with the top on, but you might need a different style dial indicator, as in a 90 degree test indicator type, but maybe not.
Tilt the arbor to the 45 degree stop, it’s just less bending over that way.
Take the belts off. Not mandatory but makes it easier.
I had just over .002” when I started on this saw. That’s with brand new bearings that I just installed. In less than an hour I had it down to under .001” which is the amount of each graduation on this indicator. It was moving less than one line, I could have got out a test indicator that goes down to .0001” graduations, but thats pretty much overkill. I suspect that these C1/C3 bearings won’t do much better than .0005 anyway and I can guestimate that by looking at the dial of this one.
If you have an arbor thats appreciably worse than this, as in .006” or more, you can still true it this way, but it might be easier to do it with the top on, put a dremel type grinding stone in your router, clamp the router to the table with it very close to the arbor and use the blade tilt to slowly ease it into the stone in your router. You would color the whole surface of the arbor the contacts the blade and just grind it until you removed the coloring all the way around the circumference and stop right there. Glad I didn’t have to go that way!