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Connor Lyons

Sharpening very hard blades

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So after a couple years of working with 1084 I feel like I've dialed in my HT method reasonably well, at least normalizing and quenching. But I have been getting somewhat inconsistent results with how sharp I've been getting them, which makes me wonder if I should adjust how much of a temper I give them.

 

I primarily like to make small edc type knives with maybe only 2" or so of actual cutting edge. So my thinking is that I can afford to have a somewhat harder blade than if it were say a 6" blade, because it's likely not going to be used with nearly as much force as a bigger knife, so therefore a catastrophic failure or chipping due to excessive brittleness is less likely.

 

So my first question here is: is that a reasonable assumption? Or is that wacky nonsense I made up? 

The reason I want an extra hard blade in the first place is because I'm also going for maximum edge hold, just cause I'd rather be sharpening a brand new knife for the first time rather than keeping up an old one! So after quenching, I usually only give the lil suckers a one hour temper @ 420 F or so and leave it at that. So what I'm left with seems to be an obnoxiously hard blade, but that's what (I think) I want.

So once I've got them all finished up and put on edge on the little fellas, this is where things get somewhat wonky. About half of my blades come out razor sharp after moving through three grits to the finest finish belt available for my little WorkSharp belt grinder doo-dad. Sharp enough to push cut through thin paper and shave the hair off my arm. The other half of my blades come out pretty dang sharp, and can slice paper pretty well, but not shaving sharp. Im also pretty dang meticulous about maintaining a final edge thickness of between .015" and .020", so I'm thinking that shouldn't account for too much of a difference in sharpness.

So do I just need better sharpening equipment? Must I finally spend the cash on a quality set of diamond stones or the like? 

What I'm most curious about is the magnification required to actually see the difference between a differently sharpened edges. Is there anyone that has used some type of microscope or other magnification to examine their edges? I mostly just think it would be a nifty way of understanding what's going on with a truly sharp blade.

 

Anyways, thanks for any suggestions or input you may have!

 

Edited by Connor Lyons

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Do you grind the edge after HT to remove the decarb? Also 420°f is a bit high for small EDCs. 400°f would be just fine. 

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23 hours ago, Joël Mercier said:

Do you grind the edge after HT to remove the decarb? Also 420°f is a bit high for small EDCs. 400°f would be just fine. 

Yes I grind the edge after HT starting with what I'd guess is somewhere around a 320-400 grit belt on the WorkSharp. 

I suppose if 400°f is sufficient for a temper that would point more towards my sharpening technique.

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1 hour ago, Connor Lyons said:

Yes I grind the edge after HT starting with what I'd guess is somewhere around a 320-400 grit belt on the WorkSharp. 

I suppose if 400°f is sufficient for a temper that would point more towards my sharpening technique.

Sorry, that's not what I meant. I'll try to explain in a better way. 

After the temper, I grind a few mils (around 0.010") off the edge before I grind my bevels. This way, I am sure the very end of my cutting edge will not be decarburized. 

Edited by Joël Mercier

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On 11/25/2018 at 1:23 PM, Joël Mercier said:

Sorry, that's not what I meant. I'll try to explain in a better way. 

After the temper, I grind a few mils (around 0.010") off the edge before I grind my bevels. This way, I am sure the very end of my cutting edge will not be decarburized. 

Ahhh I see what you mean now. I have not tried that but I'll definitely give it a shot on my next one!

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You should do a least two temper cycles. How thick is your edge prior to sharpening? A thick edge will be way more difficult to sharpen than a thin edge. I take my edc blades (3-4") to around .010 before sharpening.

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