Testing the Edge

A place to share, learn, & show off sharpening tips, tricks, techniques, & tools for sharpening edges of all kinds.
StrawHat
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Testing the Edge

Post by StrawHat »

I see in this section many threads about various ways to achieve a sharp edge. What I do not see is how you are testing that edge to determine if it is sharp.

So, boys and girls, what is your favorite method for testing the edge of a newly sharped blade?

Thank you.

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fergusontd
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Re: Testing the Edge

Post by fergusontd »

::tu:: I usually take a piece of paper and slice the edge. That's sharp enough for me. ftd
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Re: Testing the Edge

Post by royal0014 »

Usually plain old paper to see if I'm making progress.
Then shave off a patch of arm hair (I have plenty ..) Both sides of the blade.
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Re: Testing the Edge

Post by Steve Warden »

I pull it across my thumbnail. If it grabs, I'm good.
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Re: Testing the Edge

Post by Beavertail »

Steve Warden wrote: Sat Oct 26, 2019 12:10 pm I pull it across my thumbnail. If it grabs, I'm good.
Yup, the old thumbnail test for Me.
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Re: Testing the Edge

Post by Gunsil »

I see if it will shave the top of my forearm dry.
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Re: Testing the Edge

Post by Colonel26 »

I treat it worth the pad of my thumb. If it feels , then I see if it’ll shave arm hair. If it does it’s good.
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Re: Testing the Edge

Post by Doc B »

What the Colonel said ^. I might not go to shaving sharp, depending on the knife, anticipated use and steel. Seems some of the "super steels" will lose shaving sharpness with a few days or weeks of use...then hold an acceptable / user edge, for a long time. I don't fret over shaving sharpness...at the expense of metal.
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Re: Testing the Edge

Post by StrawHat »

Good ideas, all of them.

When I first started I used slick magazine paper. Fold up about 1/2” and test against that. Then I progressed to the yellow pages. Then to cash register tape. I now use 3” thermal cash register tape. It comes in rolls so it is easy to carry and use. It is not quite flimsy but you need a sharp edge to slice it. I try the edge about an inch from my fingers.

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Re: Testing the Edge

Post by XX Case XX »

Steve Warden wrote: Sat Oct 26, 2019 12:10 pm I pull it across my thumbnail. If it grabs, I'm good.
X2. ::tu::

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Re: Testing the Edge

Post by btrwtr »

I do the thumbnail test. Pull the entire length of the blade choil to tip across my thumbnail with the blade perpendicular to the floor and thumbnail slanted at about 45 deg. Just the weight of the knife and blade on the nail holding the knife at the very end opposite the blade tip.The blade should stay put as I move it and not slide off the nail. Dull spots on the blade will cause the blade to slide off the nail.

I also do the arm hair shaving test if I want a shaving sharp edge.
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Re: Testing the Edge

Post by Mumbleypeg »

Same here as several have said already. I use the "pad" of my thumb to feel the edge. With a little experience feeling various edges you can tell how sharp it is. I also use the hair on my arm to test for shaving but rarely sharpen my knives to that point. I just don't find a shaving edge to be needed and sometimes it's a detriment.

I did encounter one knife, a custom fixed blade my son bought at a gun show, that was so sharp it cut my thumb when I felt the edge. Sharpest knife I ever saw! ::woot::

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Re: Testing the Edge

Post by Railsplitter »

At home I usually use phone book paper for the initial test but my favorite way to test sharpness is to cut some shrink wrap while it's tightly wrapped around a pallet. We have hundreds of shrink wrapped pallets at my workplace on any given day.

Once I get the blade sharpened to my satisfaction I'll take the knife to work with me and do a final test on some shrink wrap. The shrink wrap is delicate and it responds well to any imperfections that I might have missed along the edge. Fortunately, I rarely need to do any follow up honing but I use the final shrink wrap test to confirm that.
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Re: Testing the Edge

Post by tongueriver »

Pad of thumb. I have very thin skin and I can tell if it is sharp enough for me to smile, very quickly this way. On a related note, I am not very good at achieving this sharpness. :(
On an unrelated note, it seems to me that knives lose sharpness to a degree, just sitting. Am I nuts?
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Re: Testing the Edge

Post by Reverand »

tongueriver wrote: Sat Oct 26, 2019 4:43 pm Pad of thumb. I have very thin skin and I can tell if it is sharp enough for me to smile, very quickly this way. On a related note, I am not very good at achieving this sharpness. :(
On an unrelated note, it seems to me that knives lose sharpness to a degree, just sitting. Am I nuts?
Probably, but that is beside the point!
Seriously, I haven't noticed that, but I imagine that the steel would be more prone to oxidation on a microscopic level when it is that thin.
Colonel26 wrote: Sat Oct 26, 2019 12:47 pm I treat it worth the pad of my thumb. If it feels , then I see if it’ll shave arm hair. If it does it’s good.
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Re: Testing the Edge

Post by jerryd6818 »

tongueriver wrote: Sat Oct 26, 2019 4:43 pm Pad of thumb.
Same here.
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Colonel26
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Re: Testing the Edge

Post by Colonel26 »

tongueriver wrote: Sat Oct 26, 2019 4:43 pm Pad of thumb. I have very thin skin and I can tell if it is sharp enough for me to smile, very quickly this way. On a related note, I am not very good at achieving this sharpness. :(
On an unrelated note, it seems to me that knives lose sharpness to a degree, just sitting. Am I nuts?
I’ve noticed some of my knives do seem to lose sharpness spring around and some don’t seem to. I have no idea why but I have noticed that.
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Re: Testing the Edge

Post by jerryd6818 »

Colonel26 wrote: Sat Oct 26, 2019 9:46 pm I’ve noticed some of my knives do seem to lose sharpness spring around and some don’t seem to. I have no idea why but I have noticed that.
That's because them boys are sneakin' 'em and trying to cut barbwire with 'em. :mrgreen:
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Re: Testing the Edge

Post by Colonel26 »

jerryd6818 wrote: Sat Oct 26, 2019 10:08 pm
Colonel26 wrote: Sat Oct 26, 2019 9:46 pm I’ve noticed some of my knives do seem to lose sharpness spring around and some don’t seem to. I have no idea why but I have noticed that.
That's because them boys are sneakin' 'em and trying to cut barbwire with 'em. :mrgreen:
Hmmmm. I do see them ogling my edc Knives occasionally. You might not be far off!
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Re: Testing the Edge

Post by kootenay joe »

I recall a thread in BF years ago in which many people posted that their knives did loose sharpness over time when in storage. Some were people who claimed to be good at sharpening and then knew the level of sharpness that they brought the edges to. Then after a year or two, this level of sharpness was no longer present.
A few metallurgists discussed the edge at the molecular level but could not account for the observed dulling.
When doing 'slice the hanging paper' test, how far from your pinch grip on the paper do you slice ? Someone has said 1". I try at about 3" on newsprint.
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Re: Testing the Edge

Post by FRJ »

After sharpening I push the edge of the blade into my thumb nail, on the flat, thoughtfully.
Blade at an angle. If it is sharp it will catch immediately.
I try this at the tang and several places up the blade to the tip. I try the other side. Same method.
If it slides I go back to the stone until I get the results I want. A sharp edge.
I can't tell you the last time I shaved hair on my arm. I'm not interested in that.
I tried to cut paper awhile back after sharpening. I was surprised it didn't cut it very well. I don't care.
I put my wonderful knife in my pocket and moved on.

I think blade edges will loose a fine cutting edge in storage. Just noticeably less sharp. I remembering this happening to me. Once.
It probably has happened without my noticing it. Of course I have no explanation for it.

Great thread. It's nice to see sharpening discussed. ::tu::
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Re: Testing the Edge

Post by 1967redrider »

I cut a ripe tomato. If it cuts easily it's sharp. If it doesn't, resharpen.
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Re: Testing the Edge

Post by FRJ »

:D
There ya' go. Tomatoes are a good test. ::tu::
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Re: Testing the Edge

Post by StrawHat »

1967redrider wrote: Sun Oct 27, 2019 1:35 am I cut a ripe tomato. If it cuts easily it's sharp. If it doesn't, resharpen.
I have done that when sharpening at Farmers’ Markets. Sometimes with a pepper. Except for the waste of food, a great visual test for customers to witness.

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Re: Testing the Edge

Post by Mumbleypeg »

Cutting a tomato is a lot like slicing bread. A "toothy" edge works better than a shaving edge. Same for cutting steak.

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