...
I have belts up to 2000 grit. After that, for polishing steel (or aluminum), I use 3M Trizact disks in 35, 10, and 5 micron grits in a random orbital sander and final polish with 3M Fine Machine Polishing Compound on a buffing wheel. Gives a mirror finish. (But, as I've been told many times, avoid a 'mirror' finish - it shows every flaw. (but done right it's exquisite))
With coarser grits, the heat tends to leave the piece with the ground off pieces (chips and sparks). Higher grits tend to leave the heat in the piece. So, for the same grinding speed and pressure, something being ground with a 24 grit belt will not get as hot as something being ground with a 220 grit belt. This becomes especially true at grits above about 600.
Sources
Maverick Abrasives https://www.maverickabrasives.com/
Tru-Grit https://trugrit.com/
Texas Knifemakers Supply https://www.texasknife.com
Amazon www.amazon.com
Jantz https://knifemaking.com/
Pops Knife Supply https://popsknife.supplies/
Alpha Knife Supply https://www.alphaknifesupply.com/shop/