shaving sharpness does not require fine abrasives

hardheart

hardheart

Joined
Sep 19, 2001
Messages
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Firstly, I do not mean facial hair, gotta stress that.
It happens often enough that I thought I'd start a thread on it. People will post about how they have fine ceramics, water stones, pastes, strops, etc., yet cannot get a knife to shave arm hair. They want to know how many more steps they need to add, or how much finer their abrasives need to be.

I already have a thread about sharpening with files, and it leaves a hair scraping edge, not in the same vein as what I know people are looking for. But, I followed the filed edge with my 1 x 1/2 x 6" Congress Ruby (not actual ruby, but it's aluminum oxide) in 60 grit, formed and removed the burr, and then stropped 20 passes/side with chromium oxide, and it shaves. The CrO definitely helps, but the main thing is that I went to it straight from 60 grit, not 600, not 6000. It is not a fine pushcutting edge (have to be at the point of hold to cut printer paper), it is not a highly durable edge, but it shaves arm hair. If you can do this, then you get pushcutting, durable edges in finer grits as follow-up.

What I want to stress is that you don't drop down to the next finer grit to achieve something like shaving sharp. It's working backwards, as the finer grits slow you down, removing less metal. The fine grits refine an edge, so you need to form that edge first. Practice with the coarsest grit you've got, it'll keep you honest with your angles and show you immediately when you screw up.
 
A good thread that was way overdue HH! I don't know about 60 grit, but 300ish followed by a strop makes for a pretty nice edge, very aggressive. I prefer to keep the mountain ranges a bit smaller (even at 300ish grit followed by stropping the edge looks like it was chipped), but it is certainly not needed. And if you can get an edge at that grit range shaving without a strop, you know that you are pretty damn good at sharpening :D.
 
I can easily get arm-hair shaving sharpness at 320 grit.

I normally use 320, 500, 20 micron, 15 micron, 9 micron, and strops with 6, 2.5, 1 and .5 micron polish to get a highly refined, poilished edge because I like them that way. But you're absolutely correct in that you can get a shaving edge with a very coarse abrasive/stone. :thumbup:

Ben
 
Yup, a common mistake is to try and make a dull knife sharp with a super-fine stone. Good luck with that. (You'd think I would know better.)
 
Very good thread. I get my knives shaving sharp on the brown/gery stones before moving onto the fine, uf and strop. I even got it to shave on the Diamond rods once!
 
Tom Krein said:
I sharpen on a 120 grit ceramic belt.... :D

Good thread!!

Tom
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Yah, Tom, you get tree topping from that 120 grit belt with great slicing aggression. Us mere mortals just have to gawk in awe of that. Your edges outdo even the best Spyderco egdes I have seen, and that is real impresive.

Me, on the other hand, can get an arm hair shaving edge from a 120 grit DMT XX Coarse when I finish with light stroppng strokes to remove the burr and get a clean edge. I then move on to the DMT Coarse (325 grit), where it gets to shaving real nice and smooth, then DMT fine (600 grit) where I can get some hair popping when I'm not on too many Red Bulls. It takes Spyderco ceramics or 1000 grit Glasstones for me to get to tree topping, then hair whittling usually starts occuring wth the Syderco Ultrafine or 2000 grit Glasstone if I do a great job, or on the 8000 grit Glasstone or 3M lapping film if I didn't do a good job. For extended slicing a DMT Coarse edge seems to work real nice, but I like the bragging edge of the 3M, sub micron lapping films. That level of sharpness is addicting, but not the greatest for slicing things like rope or cardboard over and over. Tom's edges last really long because they start out tree topping and also have wicked microteeth from the 120 grit belt for great long term slicing. Kind of the best of both worlds with brag worthy push cutting and great slicing agression.

But, back to the point of the thread, I always try to get my knives as sharp as possible at the coarser grits and remove any burr as I go through the stones. That way you have a good foundation layed for each progressively finer grit, and in my experience that leads to better, longer lasting edges.

Mike
 
a while back i used a 30 grit disc to work up a burr on an edge before putting it on the cardboard buffing wheel just to see what it would do. it would shave but didnt look too good. the way the burr is removed and how the edge is finished is what matters. hardheart is 100% correct.
 
The coarsest stone I have is the Spyderco Medium Sharpmaker stone and I can use that to shave easily. It's all in the technique. Great thread HH.
 
hardheart said:
Firstly, I do not mean facial hair, gotta stress that.
It happens often enough that I thought I'd start a thread on it. People will post about how they have fine ceramics, water stones, pastes, strops, etc., yet cannot get a knife to shave arm hair. They want to know how many more steps they need to add, or how much finer their abrasives need to be.

I already have a thread about sharpening with files, and it leaves a hair scraping edge, not in the same vein as what I know people are looking for. But, I followed the filed edge with my 1 x 1/2 x 6" Congress Ruby (not actual ruby, but it's aluminum oxide) in 60 grit, formed and removed the burr, and then stropped 20 passes/side with chromium oxide, and it shaves. The CrO definitely helps, but the main thing is that I went to it straight from 60 grit, not 600, not 6000. It is not a fine pushcutting edge (have to be at the point of hold to cut printer paper), it is not a highly durable edge, but it shaves arm hair. If you can do this, then you get pushcutting, durable edges in finer grits as follow-up.

What I want to stress is that you don't drop down to the next finer grit to achieve something like shaving sharp. It's working backwards, as the finer grits slow you down, removing less metal. The fine grits refine an edge, so you need to form that edge first. Practice with the coarsest grit you've got, it'll keep you honest with your angles and show you immediately when you screw up.
Click to expand...



+1! Great post.:thumbup:
 
richard j said:
....the way the burr is removed and how the edge is finished is what matters....
Click to expand...

Couldn't agree more, the quality of the edge stands and falls with the burr, or rather with how well it was removed.

Now as a chorus, please say with me:"IT'S ALL ABOUT THE BURR"! :)
 
So my question is when cutting thins like rope and stuff like that which edge lasts longer. the micro serrated edge or the polished push cutting edge???
 
Burrs are byproducts of sharpening. They can be useful in determining if the bevels meet, but if you use light pressure they may be less noticeable, or not form at all. Heavy pressure on the edge is not necessary during sharpening and can actually distort the edge you are trying to obtain. You can get a sharp, rough edge with coarse abrasives, but generally the finer the abrasive the sharper the edge. As you move up in abrasive fineness, sharpening pressure should decrease commensurately.
Bill
 
I noticed this a few years ago when sharpening a Bear Cutlery damascus butterfly knife. The edge off the coarse side of the stone would shave and cut very aggresively. Mr. Krein seems to do a good job, Bob Dozier uses a coarse edge finish from what I've heard. I managed a hair shaving edge off a 220 or 320 grit belt (I dont remeber which) without stropping. Cliff noted this many times as well, using edges off of a 100 grit belt in extreme cases. Be warned that the edges straight off the belt that I've done were with the belt running into the edge. I've never had it grab a knife, but that doesnt mean it wont.
 
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