Sharpening question.

Daniel Macina

Well-Known Member
Hey guys. I’m about to grab the Shapton 500/2000/16000 glass stone set and was going to pick up some nano cloth and some gunny juice emulsion. I can only get one or two different gunny juice right now which ones would you recommend? Thanks!
 
Glass stones are excellent stones!! They cut high alloy and lower alloy nicely and quickly.

What types of knives are you sharpening? First time using water stones? I would probably go with a lower grit final stone? I usually end up with a 5K edge before stropping. It retains some bite for cutting. 500, 1000-2000 and 5-6K may be a better all around option?

I usually go 320-400 (Glass Stone or Latte 400) grit to start (or rough the bevel in with the belt sander 120 belt at very low speed and wet belt), 1000-1200 grit stone medium (Bester 1200 or Nubatama 1K), 5K (Rika 5K) stone for final stone and then strop. I have been playing with the 1200 stone and stropping at 3 or 1 micron after that stone and get a wickedly sticky sharp edges with some nice bite to it. Sharpening very wear resistant steels with a 16K stone after a 2K stone will take more time, and may introduce more wobbles to your edge bevel, leading to a worse edge.

I have strops with 16, 8, 3/2, 1, 1/2 and 1/4 micron compounds (CBN or Diamond) and I have been finding that I really like the edge off of the 16 micron strop followed up by a 3 micron strop. I used to do the 8 micron then 2 micron off the 5K stone, but the 16micron 3 micron combo seems to work better for me?

I use either leather strops or balsa strops with the compounds on them.
 
I am curious as to how many makers are hand sharpening their knives with any combination of stones etc.........I NEVER ever hand sharpen a knife as i cut new bevels on the blade with either a 120....240....320... grit belt depending on the edge i want and polish off the burr on my buffer and i am done....i have excellent results doing this.....i am sure that there are lots of makers doing the same.....is this a fear of the buffer thing or something else? I have been doing this for a very long time and the results are fantastic
 
I am curious as to how many makers are hand sharpening their knives with any combination of stones etc.........I NEVER ever hand sharpen a knife as i cut new bevels on the blade with either a 120....240....320... grit belt depending on the edge i want and polish off the burr on my buffer and i am done....i have excellent results doing this.....i am sure that there are lots of makers doing the same.....is this a fear of the buffer thing or something else? I have been doing this for a very long time and the results are fantastic
I use my disc grinder with some 400 at a low speed and then buff. A lot of people sharpen to high grits, but I just read in one of Larrin Thomas’s articles that for CATRA testing he sharpens to 400 grit. He said that has consistently shown to be the grit that gives him the highest edge retention. I’ve always done 400 because I like how it cuts.
 
I use different grit belts for different uses.....I use 120 grit belts slightly used for fillet knives if they are cutting thru the rib cage bones.....the finer grits dont want to cut thru the bones as easily......i also sharpen ice auger blades with 120 as the finer grits shave the ice and are not agressive enough...if i am sharpening skinning knives for trappers that are just used for removing the hide i use finer grit....I would think that anyone hand sharpening does something similar......
 
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.
 
I am curious as to how many makers are hand sharpening their knives with any combination of stones etc.........I NEVER ever hand sharpen a knife as i cut new bevels on the blade with either a 120....240....320... grit belt depending on the edge i want and polish off the burr on my buffer and i am done....i have excellent results doing this.....i am sure that there are lots of makers doing the same.....is this a fear of the buffer thing or something else? I have been doing this for a very long time and the results are fantastic
I'll do the initial sharpening on the grinder running at a very slow speed. I've been starting at 400 and going up to 800. But based on what EdwardHandmadeKnives said I'll will go to 400 next time. After the initial grind, I have a water stone that is 1000 on one side and 4000 on the other. I'll hand sharpen on that until I can cut paper cleanly. Then I strop on a piece of leather with green compound and then check sharpness again.
 
I have read the concerns about edges not holding up when they've been sharpened on belts. I think it's an academic argument, because I am not seeing that issue in real life. I think it's the geometry versus the steel's ability to hold that geometry. For reference: My edges are about .010 - .015 when they come off the grinder. I used to go down to .005 - .010 but I discovered that during hand sanding I could actually damage the edge. That was too thin and those knives probably did have edge retention issues until they'd been sharpened two or three times. That isn't a function of removing softened steel, it's the result of removing the peak of a wedge. Every time you sharpen a wedge it gets thicker at the apex. So, in my opinion it's an edge stability issue, not tempering. Then again, I have no idea what other people are doing on their belt grinder. Maybe they are cooking the snot out of the edge. I can only speak for myself and my own knives.

Ever since I made the change in my process to finish grinding my bevels at a thickness of .010 - .015 I have not had an issue, and these are kitchen knives. .010 at the edge of a 2 inch wide blade that is .090 at the spine is a very narrow wedge indeed. .005 was paper thin. On those I probably removed enough metal during initial sharpening that the blade ended up .010 - 0.15 behind the edge anyway, so what's the point of going that thin, I figured.

I sharpen on a worn out 220 belt then a worn out 600 grit belt, then strop on leather with green chrome rubbed on the leather. That leaves a toothy enough edge to cut meat and tomatoes without slipping.

I love using stones, but the belt method works great and I like convex edges. My kitchen knives are used daily and they get sharpened two or three times a year. This has been confirmed with a lot of my customers who rave about the edge holding ability of their knives and I'm using basic AEBL. (or as we discussed in another thread, Aldo's version of it.)
 
This is a terrific thread, love the insights and opinions on how we all sharpen blades. Here's my 2 cents:
I now only use 2x72 belts to sharpen. Depending on the blade condition, I'll start with 120 on thick edges (if necessary), then 220, 400. 800, (or occasionally 1200 to 2400) then stropping with a leather belt using white polish or Tormak paste.
The grinding belts are run very slow, 15-20%+/-. using belts that have sharp (new) grit. New belts with sharp grit cut cooler than old, worn belts. Using gentle pressure on the blade, with sharp grit, nearly eliminates heating of the blade edge. It requires a very light touch on the blade edge and should never show any sparking. I stopped using coolant some time ago since it didn't seem to offer any benefits. I disagree with those that believe belt grinding overheats the blade edge. If the grinding is done slowly and lightly the blade never sees any temperatures that will affect the heat treatment - at least that's my experience.
Belts are run in reverse on a solid horizontal platen. That gives a flat sharp secondary grind without any convexing due to belt flexing and gives a clear indication of burr formation. I'll run the belt in the forward direction, against the edge very lightly, for a few belt rotations to remove most of the burr. And, then use cardboard cross cuts to remove the remaining burr before finishing to a mirror edge with a leather stropping belt on the 1x42 machine.
I'm still debating whether it's best to strop after 400, or go all the way to 2400 then strop. When stopping grinding at 400, a magnifier sure shows a lot of grind marks across the cutting edge which, as some folks argue, may actually enhance the cutting edge.
Anyhow, that's my current process - and I'm always tinkering to figure out a better way. There's lots of ways to get to a really sharp edge, this happens to be the one I'm using now.
 
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New belts with sharp grit cut cooler than old, worn belts. Using gentle pressure on the blade, with sharp grit, nearly eliminates heating of the blade edge. It requires a very light touch on the blade edge and should never show any sparking.
I agree with that totally - never understood the idea of using worn out belts for sharpening. We're always told to use new sharp belts for bevels because the worn belt cuts slow and creates too much heat. Why doesn't that apply to sharpening? The only worn out belt I use for sharpening is an old "J" weight turned backward with green compound applied. This is ran at slow speed around 300 SFPM
 
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