Razor sharp edge above 30 degree angle?

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@knifenut

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Sep 4, 2014
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I have a tormek t7 that I have been using to sharpen various type of knives. This machine can do razor sharp edges on knives with angles 30 degrees and below, but when it is around 30 degrees and above, it can't do a razor sharp edge anymore. I made a 35 degree cutting edge on this D2 steel 1/4 thick hunting knife. It's sharp when I do the thumb test, but cant pass the paper cut test. Any advise is greatly appreciated.
 
Are you talking about 30 degrees per side, or 30 included?
 
^ had it been 30 DPS that would have been your problem. :D I just wanted to make sure I understood the problem.

some thoughts:

15 DPS is pretty acute, so there isn't a lot of mass in the edge. It's not difficult to overheat something like that with powered sharpening. Be sure you're not cooking the very apex of the cutting edge ,--- it's way more common that a lot of people think.

I assume this is done edge trailing, not edge leading. You'll get a wire edge that needs to be dealt with. Some people try to buff this off, but I believe that's not always ideal.

In my experience (sharpening hundreds of knives per year) when you think you're done go back to the previous side and give it one really light pass. That will push a very minor burr to the other side. Then, edge leading, swipe that burr off with a light micro bevel on a fine oil stone. This doesn't leave much of a burr at all. A few passes on a strop and you have a very sharp high quality edge.

just my .02

I use a different system than yours so my experience may not be valid in your situation.
 
That Tormek he's talking about actually sharpens with the edge leading with the stone and then following on the leather wheel. Also, the grinding wheel turns through a troth of water and pulls it up to the top of the wheel, where the knife makes contact. That, in conjunction with its super slow rpm probably prevents the edge from heating up too much. I just got a Grizzly clone of it a while back but haven't done a ton of sharpening with it.

As far as the whole "razor edge" thing is concerned, there's no such thing on a knife. Unless it's a razor/kamasori then it's not "razor sharp." The edge on a straight razor is insanely acute. I've been working on straight razors lately and it's a whole other ballgame.
 
The tormek machine is a precise sharpening machine. It uses an angle tool which keep a consistent angle when sharpening the edge. I'm just curious if of you guys have the same issues when sharpening at an angle of above 35-40++ degrees... The knife will be sharp, but will not get the same result as the below 30 degrees....

https://www.youtube.com/watch?v=zFmGfDULpiQ
 
@knifenut said:
I have a tormek t7 that I have been using to sharpen various type of knives. This machine can do razor sharp edges on knives with angles 30 degrees and below, but when it is around 30 degrees and above, it can't do a razor sharp edge anymore. I made a 35 degree cutting edge on this D2 steel 1/4 thick hunting knife. It's sharp when I do the thumb test, but cant pass the paper cut test. Any advise is greatly appreciated.
Click to expand...

If it is not a diamond hone but a stone, it will lose its "flatness", becoming concave, and this will give you more rounded edge bevel sides, which will cut poorer (like a convex edge does).

30 degree inclusive is pretty minimal for acceptable sharpness: Micro-bevels can be a tad higher, but basically 30 inclusive, and maybe with a very tiny 40-44 degrees micro-bevel, are the maximum angles that are useable without being a danger to the user, due to the excessive force required above that.

Shaving sharpness is meaningless for performance. Paper cutting is barely any better than shaving, but is indicative of apex condition.

Gaston
 
It's probably not too helpful but all of these A-2 blades are way beyond 30° (you can see the angles written on the blades with magic marker). One is up to 54°. All are single bevel (flat back on one side).

They are ALL absolutely hair whittling. I can easily shave curls off a single hair while it is in my arm . . . every time I sharpen. I just use the jig and go through the motions with a few stones and I KNOW without testing it will be that sharp. I test one occasionally on a hair and am pretty much never disappointed. I use a jig. Lots of the wood worker people use tormeks and get similar results, maybe not this good but at least shave sharp on similar angles. I just use Shaptons and a jig (Nortons were great too).

So it is just a matter of holding the blade. I am not sure if you are asking can the Tormek make it or if the wider angle can make it but I'm pulling' for yah . . . we're all in this together..

 
Here are a few links to a friend’s blog who uses a Tormek among many other sharpening methods.
He really knows his stuff. Works the Aussie wood too. Doesn’t get any tougher than that for sure for sure.

http://www.inthewoodshop.com/WoodworkTechniques/GrindingNirvana.html
http://www.inthewoodshop.com/WoodworkTechniques/IsTheTormekAGrinderOrASharpener.html

And the home page =

http://www.inthewoodshop.com

Maybe even converse with him, he’s a smart guy. Maybe he is into knives. We only banged the table about woodworking and cars.
 
Nathan the Machinist said:
Some people try to buff this off, but I believe that's not always ideal.
Click to expand...

Verhoeven did a nice study in 2004 - Experiments on Knife Sharpening, it's available free online
page 25 he does some work with the Tormek and then a little on discussion that buffing wheel :)

I've found that finioshing with a loaded leather strop is key for my sharpening process and Verheoeven confirms the value of this
You may try the loaded leather strop and see if that makes the final difference for you
Verhoeven is great reading, particularity since you have a Tormek, :)

just FYI, this is the summary on the buffing wheel, the whole section should be read

available here - https://www.wickededgeusa.com/wp-content/uploads/2012/10/knifeshexps.pdf

verhoeven_zpsrm21vrjv.jpg
 
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How are you measuring the angle? I think the tormek angle finder may not be accurate if you check the angle off the bevel, you may be adding in the bevel angle. I don't know this, but just looking at it, it seems like that would happen.

What is the paper test? Just slicing paper?
 
please stop using "razor sharp" cause you never want that on any tool not ment to cut hair.

i make straight razors and the true "razor sharp" falls in the range of 15-22 DTA with no burr on the edge and under 1 micron thick at the very edge
when i started makign knife i thought shavig sharp was hair off my arm then i started making kitchen knive and found new level sharpness that didnt pull when "shaving arm hair" now i know a razor is sharp if you can cut the hairs on your arm or leg without touching the skin under the hair. you read that right the edge is so sharp that the hair is cut before hair can flex out of the way nearly a CM away from the skin (its spooky when you first see it )
 
^AWSOME.
I like it when people saw off half their skin just to put a hair or two on the blade to say it shaves :thumbup:
 
Nate, the Tormek runs rather slow and is a wet wheel grinder.
Nathan the Machinist said:
^ had it been 30 DPS that would have been your problem. :D I just wanted to make sure I understood the problem.

some thoughts:

15 DPS is pretty acute, so there isn't a lot of mass in the edge. It's not difficult to overheat something like that with powered sharpening. Be sure you're not cooking the very apex of the cutting edge ,--- it's way more common that a lot of people think.

I assume this is done edge trailing, not edge leading. You'll get a wire edge that needs to be dealt with. Some people try to buff this off, but I believe that's not always ideal.

In my experience (sharpening hundreds of knives per year) when you think you're done go back to the previous side and give it one really light pass. That will push a very minor burr to the other side. Then, edge leading, swipe that burr off with a light micro bevel on a fine oil stone. This doesn't leave much of a burr at all. A few passes on a strop and you have a very sharp high quality edge.

just my .02

I use a different system than yours so my experience may not be valid in your situation.
Click to expand...
 
HSC /// said:
Verhoeven did a nice study in 2004 - Experiments on Knife Sharpening, it's available free online
page 25 he does some work with the Tormek and then a little on discussion that buffing wheel :)

I've found that finioshing with a loaded leather strop is key for my sharpening process and Verheoeven confirms the value of this
You may try the loaded leather strop and see if that makes the final difference for you
Verhoeven is great reading, particularity since you have a Tormek, :)

just FYI, this is the summary on the buffing wheel, the whole section should be read

available here - https://www.wickededgeusa.com/wp-content/uploads/2012/10/knifeshexps.pdf

verhoeven_zpsrm21vrjv.jpg
Click to expand...

Very interesting article :)
 
If "shaving sharp" isn't a good test, and paper is marginally better, what is a good method for testing sharpness? When I slice paper I'm looking to feel any inconsistency in the cut. I rarely shave my arm because I end up looking silly. I started slicing leather scraps with one blade, similar to how you would paper, but that would get expensive. The only other one I know of/use is pressing the blade down through a stack of index cards/notebook/phonebook, and that makes a mess.

I'm talking general use or hunting blades, not razors.
 
kuraki said:
If "shaving sharp" isn't a good test, and paper is marginally better, what is a good method for testing sharpness? When I slice paper I'm looking to feel any inconsistency in the cut. I rarely shave my arm because I end up looking silly. I started slicing leather scraps with one blade, similar to how you would paper, but that would get expensive. The only other one I know of/use is pressing the blade down through a stack of index cards/notebook/phonebook, and that makes a mess.

I'm talking general use or hunting blades, not razors.
Click to expand...

those are all fine, and then try some 5/8" or 3/4" manila rope, slicing cuts
It is true that a push cut through paper will tell you about inconsistencies as you mentioned,
But paper tends to move out of the way, vs leather
 
Slowly cutting paper can show where the edge still needs attention for sharpening.
 
for my kitchen knives i like the paper test but not to see if its sharp its more for to see if i have edver last bit of wire edge off the blade (i sharpen the burr off not strop)
as you slice thin paper (i like MSC fliers) any drag at all will sound different and likely start a tear not a nice smooth cut
 
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