Many people complain knife edges don't last or chip easily and the common reply is that the edge is sharpened with a belt sander and/or buffed, which can overheat the edge too much, weakening the steel and to sharpen it fully a couple times to remove the damaged/weakened/overheated steel.
I combine stones and the belt sander. I used my variable speed belt sander to cut the bevel to rough it in with a 120 belt on most knives. I use slow speeds and often wet the belt too to keep any heat generated down. Very thin edges or zero ground edges like kitchen cutlery, I may just use my 320 Glass Stone to cut the bevel and stones/strops from that point.
Some knives, I go from a 120 belt to a A30 Norax (or other belts in the 400-600 range) slack belt to clean up the bevel, and then a linen belt with some 2000 grit compounds on it to buff/polish the edge and remove the burr. Gives a beautiful convex edge that is stupid sharp and shiny! The Norax I have can't be run wet, so I go very slow so I don't over heat the edge or use a belt I can run wet.
On good, hard steel kitchen cutlery, after I rough in the bevel, I start with stones and work up to the Rika 5K edge and then strop. I grind my kitchen knives to a near zero edge, so I had sharpen on water stones to make sure I don't over heat the edge. I often to from the 5K stone to a 2 or 1 micron strop, but have been playing with toothier edges lately for kitchen knives. Japanese kitchen knives I usually do all with stones unless I need to use the belt sander to reprofile, regrind, thin, repair, etc. Soft steel like Henckels, Wustoff, Victorinox, etc, 120 belt, 400 belt and strop and call it good.
Hunters/EDC/Camp type knives, I do the bevel roughed with the belt, then a 1200 stone and then strop on compounds between 8 and 1 micron. This helps keep some toothiness to the edge so it cuts aggressively, especially with skinning/meat slicing tasks. I really like this on harder to sharpen steels!
There have been studies done that show using a belt sander/buffing can weaken the very edge due to the heat generated by grinding without coolant. The theory is that because the edge area is so thin, dry sanding can overheat the thin steel very quickly and make it softer at the very edge, which leads to less edge retention since the steel is softer. Since the steel is often removed quickly, you don't see the colors of the heat on the blade due to not having the time to show the heat or the effected metal being removed. If you turn the steel colors after hardening, you can grind the colors off the blade and still have softer steel under the coloring. From what I remember reading about the study and the results was supposedly that the hardness was much less at the very edge than a mm or two back due to the heat travelling. As the blade gets thicker, it takes more heat to cause issues. Some people use the belt sander to rough, and then stones to recut the bevel so if anything was overheated, it will be removed by the coarse stone so they get back into "good" steel.
I also know that when knives are blanked out from sheets, sent for heat treating and then ground, there may be a thin layer of decarb (maybe .010 to .020) around the profile of the knife, which will have less hardness. If you were to grind a knife and sharpen it without removing that thin layer on the edge, you may also have a softer edge. Laser or plasma cutting the blanks may leave a larger HAZ (Heat affected zone) around more of the perimeter of the blank that may have the steel super heated before heat treating that may also cause issues. Water jet cutting shouldn't really have a heat affected zone.
I leave my blanks oversized before HT and then grind the final profile afterwards. I wonder how many of the "belt sander burned my edge" issues are from that decarbed steel not being removed and still being left on the edge from the factory and not the edge being overheated?? I saw a factory take a hardened blade blank, stick it into a machine to grind it (water cooled CNC machine), then polish, buff and sharpen the blade, so the very edge of that blank that can still have the decarb may not have been fully removed! Sharpening should remove that small portion, but theoretically, it may still be there to some extent?
For me, I try to keep the blade as cool as possible and do most of my grinding after heat treating. Keep belt speeds slow and wet to not overheat the very edge.
