Strage results when sharpening my Shiro 95T

bgentry said:
Well, I'm not trying to be combative here. I admit my post was kinda short.

But the idea that all dry belt grinders ruin the heat treat of a knife is also rather hard to believe. That means every Spyderco ever shipped has a burned edge. Do you believe that? I don't.

Brian.
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You keep saying, "knife". We are talking about the very edge 'apex'. You can overheat the tiny bit of steel at the edge apex without feeling the heat in the thicker steel of the rest of the knife. Read Dr. Larrin Thomas's article that I supplied the link to fcol.

Yes, if Spyderco sharpens their knives with a dry belt then there's a real good chance that the heat treat is bad at the edges. But a couple of sharpening's, or a reprofile, 'without' using a dry belt should get you down to some good steel.
 
000Robert said:
You keep saying, "knife". We are talking about the very edge 'apex'. You can overheat the tiny bit of steel at the edge apex without feeling the heat in the thicker steel of the rest of the knife. Read Dr. Larrin Thomas's article that I supplied the link to fcol.

Yes, if Spyderco sharpens their knives with a dry belt then there's a real good chance that the heat treat is bad at the edges. But a couple of sharpening's, or a reprofile, 'without' using a dry belt should get you down to some good steel.
Click to expand...

I understand the argument. I've been reading these claims here for nearly 10 years now. Believe me, I get the idea. Please give me a little credit.

My experience seem to indicate that this is not an issue. Perhaps I should do some experiments of my own to see if, in my real world use, this makes any difference that I can discern.

Thanks,
Brian.
 
bgentry said:
I understand the argument. I've been reading these claims here for nearly 10 years now. Believe me, I get the idea. Please give me a little credit.

My experience seem to indicate that this is not an issue. Perhaps I should do some experiments of my own to see if, in my real world use, this makes any difference that I can discern.

Thanks,
Brian.
Click to expand...

Well it just seemed like you didn't read the other comments or Dr. Thomas's article. Friction causes heat and it doesn't take much friction to heat up the tiny bit of steel at an edge apex.
I was curious how much heat would build up on an edge apex with just a diamond stone being used to sharpen the edge, like with my Wicked Edge 130. I think it would be interesting but I don't have a high-speed thermal microscope. Someday someone will investigate it. But I sharpen slow and use minimal pressure with my diamond stones just in case. I just absolutely detest wasting good steel.
 
000, I would think it would raise the temp at the apex using your WE or my Hapstone or what ever, but raising the temp is different than heating the steel. And as far as that goes, even with a Work Sharp belt, touching up the edge with a quick pass or two will heat it, but probably not enough to re temper it. Now if you are reprofiling a blade from 35 to 15 degrees that may be a different story. And with what belt? It seems to me all the grinding they do at the factory would change the temper, But I own a few Carothers Knives and from the factory they will cut through stuff that would make a powered saw blush. So, again depending on how its done makes a major difference in effect on the steel.
I personally have enough crap going on that I refuse to stress on whether I split the hair evenly or not.
 
I'd expect the softening effect of belt grinding to be greatest on knives with thin blades and thin edges. Although the very apex is tiny no matter what the blade geometry, the metal behind it acts as a heat sink. The more metal, the lower the heating of the apex or the area just behind the apex.

My Shiro 111 has edge shoulders 0.02 inches wide. And it's a full flat grind blade. It's much more vulnerable to edge softening than the average Spyderco.

My Vanax gyuto kitchen knife, made by Bluntcut, is 0.007 inches (seven thousandths BTE) on a stock of 0.06 inches, with a full flat grind and full distal taper. I wouldn't think of using a belt grinder on that blade.

Larrin's piece is an excellent presentation on the general effect of edge damage caused by belt grinders, but it doesn't give much detail on the variables that enhance or reduce that effect. Some steels may be more vulnerable than others. Some belt grinding techniques are certainly powerful variables, for good or ill. Some hardness levels may be more vulnerable than others. Certainly blade geometry, especially at the edge shoulders, is a major factor.

A lot we don't know.
 
sickpuppy1 said:
000, I would think it would raise the temp at the apex using your WE or my Hapstone or what ever, but raising the temp is different than heating the steel. And as far as that goes, even with a Work Sharp belt, touching up the edge with a quick pass or two will heat it, but probably not enough to re temper it. Now if you are reprofiling a blade from 35 to 15 degrees that may be a different story. And with what belt? It seems to me all the grinding they do at the factory would change the temper, But I own a few Carothers Knives and from the factory they will cut through stuff that would make a powered saw blush. So, again depending on how its done makes a major difference in effect on the steel.
I personally have enough crap going on that I refuse to stress on whether I split the hair evenly or not.
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Sick, Nathan doesn't use dry belts.
 
Ah a topic near and dear to me. I have seen the effects of dry grinder sharpening first hand and haven’t done it in years.

For reference, the picture posted on the previous page is high speed steel, tempered likely in the 1000 degree F range. It had a loss of 7 points of hardness, 65-58. It’s also noteworthy that the temperatures near the surface were likely high enough to regarded the steel, leading to higher surface hardness of 62 that drops to 58 then increases back to the bulk hardness of 65. Dry grinding rehardened a steel with an autenitizing temperature of 2000+ degrees F.
 
I've seen edge holding pick up after the factory edge in every factory produced knife I've ever used/tested. Some are much worse that others, but all are fatigued from dry belt sharpening to some degree.
 
Does anyone have tips on how to sharpen the Shiro Quantum on the edge pro apex? Like previous poster I noticed the bevel is very narrow and don’t want to widen it unnecessarily . Can I use the FFG portion on the blade table and set angle to 18 using the angle grinder and calculations on the FFG ? Anything special needed to sharpen the belly portion?

What do these shiros typically come from factory at ? 18 dps ?

I was having trouble with S45VN with the stock edge pro stones so already purchased diamond matrix stones . Assume will need it for the m390 .

Photo for reference
 

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Jetlau3 said:
Does anyone have tips on how to sharpen the Shiro Quantum on the edge pro apex? Like previous poster I noticed the bevel is very narrow and don’t want to widen it unnecessarily . Can I use the FFG portion on the blade table and set angle to 18 using the angle grinder and calculations on the FFG ? Anything special needed to sharpen the belly portion?

What do these shiros typically come from factory at ? 18 dps ?

I was having trouble with S45VN with the stock edge pro stones so already purchased diamond matrix stones . Assume will need it for the m390 .

Photo for reference
Click to expand...
Stock Shiro DPS is usually right around 24 degrees. That is partial how you get the short edge profile. You can absolutely set it to 18 degrees, but the edge profile will grow if you do.
 
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