A New Toy

[ken hatch]

I picked up an Edge-On-Up cutting edge tester the other day and have been playing with it the last couple of days. I'm not sure how applicable the test results are to woodworking but....It is nice to have quantifiable numbers relating to how sharp an edge is, to be able to say off the stones it takes x grams of force to cut the test string and if I strop that force is y less. While more testing will be needed, early results indicate stropping on hard leather with 'green stuff' will lessen the force needed to cut the test string by about 50 or so grams vs straight off the stones. Two other interesting results are stones do not make a testable difference, I've A&B using Spyderco, Ark Translucent, and Shapton 8000 glass, there is not a measurable difference between any of the three when sharpening O-1 iron. The other is freehand vs. Jig, there is also little difference, if any freehand has needed less force than using the jig but the difference is so small as to be easily in the margin of error.

More fun with cutting strings to follow,

ken

[John K Jordan]

Ken, I recently got the new PT50B model - great fun! We plan to use it to evaluate sharping techniques for wood turning tools. I have tested it with pocket knives and it shows the effectiveness of my knife sharpening machine - two belts of grit and one polishing. I also tried it on a woodturning skew chisel sharpened by hand on a 600 grit CBN Tormek wheel with hard leather stropping - I'll compare it to 1200 grit when that wheel arrives. At very minimum, the sharpness tester adds some objectivity to a sharpening evaluation.

BTW, these are available on Amazon Prime now: https://www.amazon.com/Edge-Up-Sharpness-Tester/dp/B06X6GL4XS

JKJ


I picked up an Edge-On-Up cutting edge tester the other day and have been playing with it the last couple of days. I'm not sure how applicable the test results are to woodworking but....It is nice to have quantifiable numbers relating to how sharp an edge is, to be able to say off the stones it takes x grams of force to cut the test string and if I strop that force is y less. While more testing will be needed, early results indicate stropping on hard leather with 'green stuff' will lessen the force needed to cut the test string by about 50 or so grams vs straight off the stones. Two other interesting results are stones do not make a testable difference, I've A&B using Spyderco, Ark Translucent, and Shapton 8000 glass, there is not a measurable difference between any of the three when sharpening O-1 iron. The other is freehand vs. Jig, there is also little difference, if any freehand has needed less force than using the jig but the difference is so small as to be easily in the margin of error.

More fun with cutting strings to follow,

ken

[ken hatch]

Ken, I recently got the new PT50B model - great fun! We plan to use it to evaluate sharping techniques for wood turning tools. I have tested it with pocket knives and it shows the effectiveness of my knife sharpening machine - two belts of grit and one polishing. I also tried it on a woodturning skew chisel sharpened by hand on a 600 grit CBN Tormek wheel with hard leather stropping - I'll compare it to 1200 grit when that wheel arrives. At very minimum, the sharpness tester adds some objectivity to a sharpening evaluation.

BTW, these are available on Amazon Prime now: https://www.amazon.com/Edge-Up-Sharpness-Tester/dp/B06X6GL4XS

JKJ

John,

I don't turn, at least to speak of, at best I can make a replacement chisel handle if needed.

Over the years I've developed beliefs and methods of sharpening that work but sometimes changes are hard to evaluate such as different stones and different strops. It will be interesting to quantify those changes. I've already shown stropping will increase the sharpness by about 25%. Now the next question to explore is does stropping also, as I expect, increase edge life.

The other thing I shown at least to my satisfaction sharpening O-1, is type of stone makes no never mind. Even my very high dollar natural water stones will only get you to about the same place as a very inexpensive Spyderco. Let's see should I use a $2000 USD natural waterstone or the $50 USD Spyderco today. It's kinda a no brainer. The one big area I have not looked at is edge life and there could be some surprises there but I doubt there will be.

ken

[Jim Koepke]

[edited]
I've already shown stropping will increase the sharpness by about 25%. Now the next question to explore is does stropping also, as I expect, increase edge life.

ken

My thought on this is theoretical. At the same bevel angle with the same amount of wear occurring on each cutting stroke then the sharper edge will take a few cuts before it gets to the same state as the less sharp edge. If that is a valid thought process then it only stands to reason the edge that starts sharper will be acceptably sharp longer than the one starting less sharp.

Of course having it quantified with a fancy piece of test equipment is more fun than reasoning out something like this.

jtk

[ken hatch]

My thought on this is theoretical. At the same bevel angle with the same amount of wear occurring on each cutting stroke then the sharper edge will take a few cuts before it gets to the same state as the less sharp edge. If that is a valid thought process then it only stands to reason the edge that starts sharper will be acceptably sharp longer than the one starting less sharp.

Of course having it quantified with a fancy piece of test equipment is more fun than reasoning out something like this.

jtk

I expect your reasoning is correct but there could be other factors as well such as smoothness of the edge (two edges could have the same angle but one smoother than the other) and stropping helps remove the wire and removing the wire with a strop could also increase edge life. I have a 32000 grit waterstone which should give an edge smoother and at least the same angle as stropping. I will A&B sharpening on either an oil stone or Spyderco with strop vs. the 32000 grit waterstone without strop and test edge life.

It may be several days before I get around to it but stand by for more meaningless numbers.

ken

[John K Jordan]

Now the next question to explore is does stropping also, as I expect, increase edge life.


A friend and I plan to work together to evaluate edge life, not specifically the difference between stropping or not, but in the life of various types of steel used in lathe tools. For example, I and others have the subjective "feeling" that the 10V steel in Thompson lathe tools will outlast the HSS in, say, a Sorby tool. We hope to put some numbers on this. One idea is to sharpen different skew chisels as closely to identically as possible and check the fresh edges on the sharpness tester. Then make a series of cuts on, say, a simple cylinder while trying to keep things like the motion and pressure the same. Then check the sharpness again.

I don't know much about standard chisels and plane irons, but from my woodturning I am convinced that stropping the sharpened edge makes a significant difference in edge life. For example, I sharpen spindle gouges on the Tormek then strop/hone with the Tormek leather wheel with their compound. If I give the bevel a mirror finish, like one of my carving tools, not only does it cut better but I believe the edge lasts longer, especially is hard wood like Dogwood or some of the exotics. (Tormek, of course, claims this is the case but I'd prefer to check it myself - that will be the subject of another test with the PT50B.) I have good microscopes and when I look at the non-stropped/polished edge, even after minimal stropping to knock of any wire edge the cutting edge looks like a rough chain of mountain peaks compared to the polished edge. I suspect these peaks break off more readily in use.

I'll be looking forward to hearing the findings of your tests.

JKJ

[Stew Denton]

Ken, and others,

Very interesting! Technical folks love numbers. I look forward to more on this. Great post.

Stew

[ken hatch]

A friend and I plan to work together to evaluate edge life, not specifically the difference between stropping or not, but in the life of various types of steel used in lathe tools. For example, I and others have the subjective "feeling" that the 10V steel in Thompson lathe tools will outlast the HSS in, say, a Sorby tool. We hope to put some numbers on this. One idea is to sharpen different skew chisels as closely to identically as possible and check the fresh edges on the sharpness tester. Then make a series of cuts on, say, a simple cylinder while trying to keep things like the motion and pressure the same. Then check the sharpness again.

I don't know much about standard chisels and plane irons, but from my woodturning I am convinced that stropping the sharpened edge makes a significant difference in edge life. For example, I sharpen spindle gouges on the Tormek then strop/hone with the Tormek leather wheel with their compound. If I give the bevel a mirror finish, like one of my carving tools, not only does it cut better but I believe the edge lasts longer, especially is hard wood like Dogwood or some of the exotics. (Tormek, of course, claims this is the case but I'd prefer to check it myself - that will be the subject of another test with the PT50B.) I have good microscopes and when I look at the non-stropped/polished edge, even after minimal stropping to knock of any wire edge the cutting edge looks like a rough chain of mountain peaks compared to the polished edge. I suspect these peaks break off more readily in use.

I'll be looking forward to hearing the findings of your tests.

JKJ

John,

Likewise I'd like to hear about what you find.

While the preliminary testing has for the most part confirmed what I believed to be true there is one inconvenient result at least from the first tests. For a long time I've advocated natural stones either Ark oil or Japanese water over man made stones. From observation of scratch patterns the natural stones left more random scratch patterns with more rounded sides than those from man made stones and I believed the resultant edge from natural stones while not as shinny was a better (sharper) edge. With testing I've found it doesn't make a rat's patootie, at least for initial testing. With edge longevity testing I may still be proven correct but for now natural vs. man made is moot.

ken

[Christopher Charles]

Hello Ken,

I'll say what others are thinking: you've taken the sickness to a whole new level :). And I would add that you should seek immediate treatment, but I'm looking forward to your results.

[ken hatch]

Hello Ken,

I'll say what others are thinking: you've taken the sickness to a whole new level :). And I would add that you should seek immediate treatment, but I'm looking forward to your results.

Chris,

Ain't that the truth :p. I've always been one of those weird ducks that enjoys sharpening, my best guess is because for most of my woodworking life I've had a dedicated sharpening bench where it can be done quickly and easily. Sharp tools are a joy to work with.

ken

[ken hatch]

If you use 300 grams as the need to sharpen point then a non stropped O-1 edge starting at 170 grams only needs three 25mm slices along the grain of white pine to exceed 300 grams. A O-1 edge stropped to 140 grams after six 25mm slices with the grain was still below 300 grams. In fact after three slices the needed push stopped at 250 grams and did not change over the next three tests.

I know apples to oranges, I need to dig the 32000 grit waterstone out and sharpen to 140 grams without stropping to make a valid test. That will follow maybe tomorrow.

ken

[James Pallas]

Somehow I see a picture of people sitting in their basements shops surrounded by great mounds of tiny pieces of string. It may even surmount their huge piles of pine end grain shavings and arm hair. The sadistical Dr Hatch grinning in the background.:D
Jim

[ken hatch]

Somehow I see a picture of people sitting in their basements shops surrounded by great mounds of tiny pieces of string. It may even surmount their huge piles of pine end grain shavings and arm hair. The sadistical Dr Hatch grinning in the background.:D
Jim

Thanks Jim, I needed that :p

I actually got back to working in the shop today. No testing, in fact the box is put up for now and I spent the day cleaning up from the Grandpeanut's toy box project along with sweeping up bits of string and cleaning out the "tool room". Now I can get to the saw vise and the Tormek and bench grinder. Goodwill maybe very happy with me.

ken

[Brian Holcombe]

Send those Natural stones my way, I will dispose of them :). What you say is true, and if I understand correctly there have been shavings as fine as 3 micron taken with edges off synthetic stones. I believe the difference is in longevity,

[ken hatch]

Send those Natural stones my way, I will dispose of them :). What you say is true, and if I understand correctly there have been shavings as fine as 3 micron taken with edges off synthetic stones. I believe the difference is in longevity,

Brian,

All I need is an address :D. I think you are correct about longevity, I just haven't figured out a good way for a valid test that is within my limited attention span....Oh look squirrels.

ken

[george wilson]

I wish you'd post a picture. Never heard of a sharpness tester.

[John K Jordan]

I wish you'd post a picture. Never heard of a sharpness tester.

George, there are pictures and more info on the Edge On Up web site: http://www.edgeonup.com/

I was skeptical at first but an hour on the phone with Mike Brubacher answered enough of my questions that I decided to buy one. Tests with razor blades showed it to be quite repeatable. The function of this is somewhat similar to the industry standard CATRA tester ( http://www.catra.org/pages/products/kniveslevel1/st.htm ) but affordable to a hobbyist and probably accurate enough.

I found out about this from Ken schroeder, "Tormak Man" who checks into SMC on occasion and moderates the Tormek forum. I believe it was he who said the Edge On Up testers are starting to be used widely by knifemakers to evaluate sharpness.

JKJ

[bridger berdel]

If I'm understanding you right Ken you're saying that the tester cannot tell the difference between stones. To me that says that either the tester lacks sensitivity in a range that is important to me or that I'm fooling myself believing that I can subjectively tell the difference in edges from different stones.

[ken hatch]

If I'm understanding you right Ken you're saying that the tester cannot tell the difference between stones. To me that says that either the tester lacks sensitivity in a range that is important to me or that I'm fooling myself believing that I can subjectively tell the difference in edges from different stones.

The unit has 5 grams of sensitivity, Results will be within a 10 gram plus or minis range, in other words 140 grams to 150 grams could be the same.

No I do not think you are fooling your self but if the test result are the same for different stones then you may have sensitive fingers, in other words your analog fingers can feel a 10 gram difference. Not bad old chap:).

ken

[bridger berdel]

how far apart do the stones need to be for the tester to register a difference? you say it doesn't distinguish between spyderco uf and surgical black ark. I doubt I can pick those out by feel, but what about the difference between say washita and surgical black? I'm sure I can feel that, in the cut if nothing else.

[Graham Haydon]

Ken, you manage to take something I'd normally roll my eyes at and turn it into something interesting and fun. It's a rare talent! I'd love to see the reading from an fine India stone and a light strop.

[ken hatch]

Ken, you manage to take something I'd normally roll my eyes at and turn it into something interesting and fun. It's a rare talent! I'd love to see the reading from an fine India stone and a light strop.

Thanks Graham, that was good for a laugh. I don't have a fine India but I expect the results wouldn't be much different that those from a hard Ark or maybe a Washita.