If you do not have a dial indicator and/or anything to sweep a decent size circle can can true the spindle the tedious way.
Take two cuts to create the step so you know which way to move the spindle after you loosen the mounting bolts.
If the spindle is mounted on a flange you need to estimate how big the step is from the 2.5" dia cutter; let's say it is .010".
Now if the mounting flange is 5" across you have to insert a 0.020" shim on the side where the cutter is cutting too deep. Tighten things down and make another cut.
Just keep on making cuts and adding or removing shims until you are happy.
HINT: Pop/Beer cans make a good source of shim stock; about 0.0025" thick I think they are.
An open mind is a virtue...so long as all the common sense has not leaked out.