Testing blade sharpness with paper?

[Frederick Skelly]

Here's a silly little thing I've been meaning to ask about...... Do any of you test sharpness by cutting paper? If so, can you please describe to me what you do?

I can sharpen well enough to take shavings on pine end grain and to pull shavings with my smoothers that are 0.002" thick. But I haven't figured out the paper test. I've tried credit card receipts, notebook paper and even paper bags. The paper will not cut by just pushing the blade into it - the paper folds, etc. And I dont think Im supposed to use a slicing motion to start the cut.

How do you folks do it?

Thanks,
Fred

[chris carter]

I find paper not reliable because there's a skill aspect to it. I used to have fun testing my pocket knife on paper and there's a technique to how you hold the paper and how you draw the knife through it that can have WILD implications on making it remarkably easier.

For plane irons I just set the edge of the iron on my fingernail. If it slides with gravity, it's not sharp. If it catches, then it's sharp.

[Mel Fulks]

Agree that it is not good test. But paper usually has a grain that makes the test easier with the right edge choice.

[Steven Mikes]

I'm a paper tester... I find only 25° bevel will push through without any slicing motion. Usually add a little slice in the motion to get it going. Also have to hold the paper behind the cut to keep it it tension. Not as hard as it sounds, and I can easily feel if there are spots on the blade that I missed based on if and where it catches on the paper.

Also like the shaving wrist hair test ;)

[John K Jordan]

Here's a silly little thing I've been meaning to ask about...... Do any of you test sharpness by cutting paper? If so, can you please describe to me what you do?

I can sharpen well enough to take shavings on pine end grain and to pull shavings with my smoothers that are 0.002" thick. But I haven't figured out the paper test. I've tried credit card receipts, notebook paper and even paper bags. The paper will not cut by just pushing the blade into it - the paper folds, etc. And I dont think Im supposed to use a slicing motion to start the cut.

How do you folks do it?

Thanks,
Fred

I sometimes test with paper when I sharpen knives. I keep a pad of PostIt notes, hold one sheet in the left hand, and push the blade into the paper. (I don't think I slice but I'll have to pay more attention next time.) My knife edge quality went way up when I got a Realsharp sharpener. I joke that the knife will slice paper dropped onto the blade but that's an exaggeration!

I don't test chip carving knives this way. After going through the four grits using the MyChipCarving sharpening kit (15 micron, 9 micron, 5 micron, 3 micron) the edge is always incredibly sharp. (On a chip carving knife you only use a short bit of the edge anyway, right at the point.)

JKJ

[Tom M King]

I quit testing a long time ago.

[Jim Koepke]

Here's a silly little thing I've been meaning to ask about...... Do any of you test sharpness by cutting paper? If so, can you please describe to me what you do?

I can sharpen well enough to take shavings on pine end grain and to pull shavings with my smoothers that are 0.002" thick. But I haven't figured out the paper test. I've tried credit card receipts, notebook paper and even paper bags. The paper will not cut by just pushing the blade into it - the paper folds, etc. And I dont think Im supposed to use a slicing motion to start the cut.

How do you folks do it?

Thanks,
Fred

Hi Fred,

The paper test is a bit tricky. It takes a very sharp blade and as mentioned already keeping the right tension between the blade and the paper. Also the lighter the paper, the sharper the blade needs to be. As mentioned paper has grain. It is usually aligned with the long direction of a sheet of paper.

Another part of the equation is as Steven said about the angle of the bevel having an influence on the results.

Also, many people find sharp is a moving target. Over time your sharpening will likely be able to pull 0.001" shavings. Your first sub thou shaving will be an exciting event.

Thin shavings seem to have a mesmerizing effect on me.

Here is one being measured after a smoother was sharpened:

Oops, the wrong image was uploaded and then removed from the body of text. It is now an attachment below.

Here is the correct image:

402742

This indicates a shaving of ~0.00025". This is still a fat shaving compared to what they do in the Japanese Kezuroukai competition.

Most of the time if my blades can cleanly pare end grain that is good enough to put to work.

One test is shaving arm hair. This is can be dangerous, especially with chisels smaller than 3/8". Some have even become upset that it is mentioned. The feel of the blade removing hair is an indicator of sharpness. Razor sharpeners use an even finer test with a hanging hair. If a blade seems to pull the hair, it is not sharp enough for cutting paper. My preference is to have a clean swath of hair removal without being able to feel the blade doing its work.

jtk

[ken hatch]

I quit testing a long time ago.

Yep, same here. If it looks sharp and feels sharp it is sharp.

ken

[Pat Barry]

If you can't cut paper its not sharp enough.

[Rob Luter]

I check on my thumbnail. The process I use always gives predictable results. I don't get wrapped up in shaving thickness as much as surface quality. Whether the shaving is .002 or .004 isn't that important to me.

[Frederick Skelly]

Thanks guys!
Jim, that sub-thou shaving is mighty impressive!

Fred

[Robert Hazelwood]

I'd say if you can sharpen well enough to pare pine end grain and take decent shavings, as you say, then there's not much need to test, just get to work. You can almost certainly get sharper than you are now, but it will come with time and experience.

That said, for some reason it is more awkward to slice paper with a plane iron or chisel than with a pocketknife. I could always do it easily with a knife- even an edge I'd consider a bit dull can still slice printer paper; sharp ones could easily do phonebook paper. But a plane iron that I know is just as sharp is difficult, or it least it was the last time I tried. It will eventually cut but you have to figure out the angle to hold it. I think the asymmetric (chisel) grind of woodworking tools is one reason it's harder.

[Doug Hepler]

Frederick

Shavings from end grain is a "real" test, but you have to reassemble the plane to test it. Arm hair and paper are much more convenient. When I run out of arm hair I use paper. Any paper will do, but I kept an LLBean catalog for this purpose. Take a new single-edge razor blade or the equivalent and try the paper test with it. That will pretty much set the standard for you. I usually have to slice a bit to get the edge in the paper. Then I try pushing without slicing. If that does not cut the paper I judge the sharpness by how much I need to slice and how hard I have to push. When an edge pases the paper test I put it back in the plane and try it out. It is almost always satisfactory.

The thread test is probably more repeatable than paper, and almost as convenient. A step up from that (or is it down, into obsession?) is a maximum force gauge. You can google both of these. Straight razor aficionados post about these fairly often.

As others have hinted, we can easily become obsessive with sharpness as an end rather than a means. That perfect "80 gram" edge won't last for many cuts in hardwood.

Doug

[John K Jordan]

The thread test is probably more repeatable than paper, and almost as convenient. A step up from that (or is it down, into obsession?) is a maximum force gauge. You can google both of these. Straight razor aficionados post about these fairly often.

Are you referring to the Sharp Check? (Sorry if this was written earlier, I didn't read the entire thread.) It measures the force needed to cut through a calibrated monofilament thread.

I have the PT50 model and it is extremely repeatable. We've used it on knives as intended but also on several lathe tools. I want to try it on card scrapers too if I can rig up an way.

402760

http://www.edgeonup.com/eou_new_2016_004.htm

JKJ

[Brian Holcombe]

Test it on the wood.

[ken hatch]

Testing just starts the dulling early.

ken

[James Pallas]

The instant you put it to work you will know. It's a good feeling when you sharpen and go to work with confidence. Every once in a while it doesn't work. You either missed a step, tried to shortcut, or something is awry.
Jim

[Bill Houghton]

Test it on the wood.
Well, yes, that'll be the final test. But I find it handy to have a test before the iron goes into the plane. I generally test the edge by "ticking" it against my thumbnail. I've tried the paper test in the past, and maybe I should think about it again; but my thumbnail's always conveniently there - no need to look for it.

[Doug Hepler]

John Jordan,

Yes, that's what I was referring to as a maximum force gauge. You are of course guided by your own interests and needs. I think a simpler thread test is easier. Make a loop 40 weight rayon thread and attach it to a weight (say 60-100 grams). Twenty U.S. nickel coins or 40 pennies weigh 100 grams. An edge that cuts the thread (without slicing) at 65 grams is super sharp, sharp enough for easy woodcarving. 85 g. is sharp enough for almost any woodworking task.

Brian,

I understand your point. I see that opinion expressed a lot. Basically I agree that cutting wood is the point of sharpening. However, it's all too easy (and a bit condescending) for an experienced hand tool woodworker to say that. Lacking your level of experience, one has to have a starting place to know what sharp enough feels like.

Doug

[John K Jordan]

The Sharp Check guy said they found single-edge razor blades to be consistently close to 50 grams. I saw that too when I tested my little tester when I first got it. Maybe I'll compare their calibrated monofilament thread with the 40 weight rayon thread you mentioned.

I like having the numbers to compare. Better than "shavin' sharp", not quite traceable to the bureau of standards.


Yes, that's what I was referring to as a maximum force gauge. You are of course guided by your own interests and needs. I think a simpler thread test is easier. Make a loop 40 weight rayon thread ...

[Jim Koepke]

What a way to spend time in the shop today, taking pictures of sharpness tests.

Here is one of my favorite paring chisels, a 1" Buck Brothers:

402788

This is right out of the drawer. It was a little chattery. The results tell a bit more:

402789

You can see whitish lines were the blade trimmed the end grain. This is caused by little nicks or rounded parts on the edge.

Here is the blade after being sharpened:

402790

The difference in the surface at the top compared to at the bottom is very noticeable.

For the record this blade is honed at 15º.

This blade will also slice paper:

402791

This paper is about the same as copy paper.

This edge would cut arm hair with a little resistance, pulling. My stones would likely need a session of flattening to get the edge any better.

My main use for thin shavings is to set the lateral on a plane:

402793

It is much easier to compare thin shavings than thick. Also with thin shavings it is more likely one side will cut and the other will not.

The other use of course is in the prevention of tear out. Super fine shavings do not pull out big divots from a surface.

jtk

[Tom M King]

The reason I like stones with "feel" is so I don't have to bother to test. I used oil stones for probably 30 years before going to water stones most of the time. The oil stones still give me the best feel, but having learned that feel on them, I can transfer it to water stones that I like. For this reason, I have no liking for diamond stones, or hard stones.

When the edge feels like you're slicing down into the surface of the stone, it's done what it's going to do. This is easiest of straight edged tools, like chisels, but does carry over to cambered irons if you have watched the swarf being taken all equally all across. This feel tells you when you can go from one stone to a finer stone too.

I don't even feel for a wire edge.

[Frederick Skelly]

You guys are great! So many good thoughts here. Thank you all, again!
Fred

[Rob Luter]

The reason I like stones with "feel" is so I don't have to bother to test. I used oil stones for probably 30 years before going to water stones most of the time. The oil stones still give me the best feel, but having learned that feel on them, I can transfer it to water stones that I like. For this reason, I have no liking for diamond stones, or hard stones.

When the edge feels like you're slicing down into the surface of the stone, it's done what it's going to do. This is easiest of straight edged tools, like chisels, but does carry over to cambered irons if you have watched the swarf being taken all equally all across. This feel tells you when you can go from one stone to a finer stone too.

I don't even feel for a wire edge.

I find the tactile response element missing with the abrasive films I use. I feel myself getting closer to the water stone rabbit hole.

[Tom M King]

I agree. No feel from films. They are handy to have for many uses though, even for things like polishing hydraulic cylinder rams to get rid of specs of rust before lubing, and shafts or bushings that seals go on.

[John K Jordan]

I find the tactile response element missing with the abrasive films I use. I feel myself getting closer to the water stone rabbit hole.

For chip carving knives I use fine abrasive strips. Works extremely well (at least for chip-carving knives!) The method substitutes procedure for feel, basically by counting strokes. The finest strip is 3 micron. BTW, these strips are the best I've seen - the adhesive backing "paper" is a strip of tough plastic or some kind, thick enough to insure a flat surface.

I like their method of mounting four strips on the edges of a square.
https://www.youtube.com/watch?v=mmUn2EXLocs

I bought extra strips from them. I want to get some full sheets to use in the in my little machine shop. https://mychipcarving.com/product/abrasive-strips/

JKJ

[ken hatch]

I find the tactile response element missing with the abrasive films I use. I feel myself getting closer to the water stone rabbit hole.

Rob,

Come on in the water is fine. Truth is good usable JNats are not much more expensive than some of the man made waterstones if you stay away from collectable stones.

ken

[Brian Holcombe]

Brian,

I understand your point. I see that opinion expressed a lot. Basically I agree that cutting wood is the point of sharpening. However, it's all too easy (and a bit condescending) for an experienced hand tool woodworker to say that. Lacking your level of experience, one has to have a starting place to know what sharp enough feels like.

Doug

I disagree. The purpose of going straight to the wood is to cutout the confusion associated with testing. The wood tells you everything you need to know immediately and a beginner is better off taking the blade in and out as many times as necessary to get it right. It will improve their ability to reset their plane.

Familiarity with process is just as important, if not more important than ultimate sharpness.

Furthermore cutting a piece of paper doesn't tell you if you're raising the bevel too highly, but putting the iron back in the plane and attempting to cut wood certainly does.

It seems to me, no different than sharpening a saw. You wouldn't likely test a saw on a piece of paper since it makes sense to cut a board with it.

[michael langman]

I can look at the edge with a loop in light and examine the edge for sharpness. And feeling the edge with my fingertips . Mostly I will just use the tool after going through the steps of sharpening and the tool is sharp enough for most work.
I have cut paper once or twice for the heck of it, but not to check sharpness anymore.

[ken hatch]

I disagree. The purpose of going straight to the wood is to cutout the confusion associated with testing. The wood tells you everything you need to know immediately and a beginner is better off taking the blade in and out as many times as necessary to get it right. It will improve their ability to reset their plane.

Familiarity with process is just as important, if not more important than ultimate sharpness.

Furthermore cutting a piece of paper doesn't tell you if you're raising the bevel too highly, but putting the iron back in the plane and attempting to cut wood certainly does.

It seems to me, no different than sharpening a saw. You wouldn't likely test a saw on a piece of paper since it makes sense to cut a board with it.

Brian or maybe it should be for Doug,

For those reasons along with the need to learn to see and feel sharp plus testing can degrade the edge. Bottom line it's counterproductive unless sharpening and testing is what blows your skirt.

ken

[Mark Rainey]

. And feeling the edge with my fingertips .
If you want to test your blade before using it, that is the best test. If you lightly brush your finger across the blade edge & it snags your skin you are sharp. The fingernail test is almost as good, especially if it really sticks sliding down the nail.

[Stanley Powers]

Here's a silly little thing I've been meaning to ask about...... Do any of you test sharpness by cutting paper? If so, can you please describe to me what you do?

I can sharpen well enough to take shavings on pine end grain and to pull shavings with my smoothers that are 0.002" thick. But I haven't figured out the paper test. I've tried credit card receipts, notebook paper and even paper bags. The paper will not cut by just pushing the blade into it - the paper folds, etc. And I dont think Im supposed to use a slicing motion to start the cut.

How do you folks do it?

Thanks,
Fred

It simply is a measure of sharpness. Not only do I try to cut the paper using the push method ONLY, but I look at the edge of the cut for ragged edges which would indicate a duller cutting edge. If that occurs, back on the power strop it goes. Sharpening is a matter of seconds this way.

[bridger berdel]

I don't cut paper or thread to test sharpness. I do sometimes shave wrist hair, especially during a demo to better illustrate the effects of honing and stropping. In the shop, not so much.