That "banding" in the pictures is really indicative of work piece or table not rigid IMO. Since these are Chinese quality machines you cannot assume your table surface is flat or the chuck bottom is flat. Run a DTI on both surfaces to make sure you don't have a concave or convex situation.So after putting new bearings in the spindle, I was still seeing runout on the grinder hub taper. So this morning I took the motor spindle off the machine. Installed it on my lathe. The motor shaft end where the TEFC fan mounts I put in the 6 jaw lathe chuck. The other end I supported in my steady rest. I initially held the shaft concentric to the lathe spindle with a center in the tail stock, and then adjusted the steady rest to hold this position.
I have a video of that setup.
Then I did the grind work on the taper;
I did some test grinds after wards using different grinding wheels.
I was stepping 0.1" per pass, and very light less then 2 tenths grinding passes.
I still see some very small ripples, and will blame this on wheel balance. But I'm very happy with this improved surface finish. I touch the corner of the freshly dressed wheel to remove the sharp edge, but still see the .1" step over in the surface finish, and if any one has advice on how to correct for this, I would like to know how to improve the finish.
I would bet my milk money that the table ways are not in full contact. The table is actually moving under the wheel pressure. Up and down as well as front to back. I have had the same banding surface on my dads surface grinder with worn ways.