Are quick sharpeners safe to use on high quality steels? do they even work?
- Thread starter Mtty22
- Start date
- Joined
- May 2, 2004
- Messages
- 6,848
The ERU is not meant to be used as a re-profiling tool. If an edge is gouged or chipped its time to be reprofiled on something thats more aggressive than this tool. The ERU is designed as a field sharpener or to be used around the shop or kitchen to "maintain edges. Where it shines is maintaining a developed edge, or following the reprofile on a coarse stone or diamond where a specific angle is used to develop the edge. Once a blade has a good edge the ERU will keep that edge sharp all week long as the knife is used and dulled. A few passes at the correct angle and the edge is bought back to sharp. All the knives we use here at my place have been maintained using an ERU, they rarely get reprofiled. For instance; if my pocket knife dulls a bit, I know the edge is at 30 degrees, I set 30 degrees on the scale and make a few passes, the edge is quickly back to sharp. When they get past a certain point, where I didn't sharpen them soon enough it is more efficient to regrind the edge on a diamond plate or using the 2 x 72 belt machine. When doing this I only grind the edge until the bulk of the rough work is done and then using the same sharpening angle I finish sharpening using the ERU. It takes just a few passes to bring the edge to a finely honed condition. This tool cleanly removes and polishes the metal and does not leave marks of any kind on the edge.
The ERU is not supposed to replace other sharpening standards, like stones or belts or the KO or others its meant to be used in conjunction with other tools. I really don't know of another tool on the market that will maintain an edge over time at a specified sharpening angle like this tool does and also fit in the palm of your hand. It can be slipped into your pocket.
The longer you use this tool to maintain your knives the more the edges become "matched Up" with the sharpener itself, to where you know a given kitchen knife is a 10 dps or your favorite EDC is a 24 inclusive. Just set the scale at the corresponding angle and sharpen.
I've been sharpening and making knives for 17 years and can put an edge on most anything metal, with a lot of different techniques and using different devices; my favorite device is the ERU; it does so many things well.
Micro bevels in minute increments, edge alignment, ascertaining existing edge angles, removing wire edges or keeping your knife edge sharp in the field.
Each one of these is made by my son and I in our shop in S/E Ohio. We do the machining, anodizing and finishing. Each ERU is fitted by hand the carbides are set and epoxied by hand, lapped and trued by hand and the sheaths, until I can afford a stitching machine, are sewed by hand.
Once that machete is sharp, the ERU will keep it working.
Fred
The ERU is not supposed to replace other sharpening standards, like stones or belts or the KO or others its meant to be used in conjunction with other tools. I really don't know of another tool on the market that will maintain an edge over time at a specified sharpening angle like this tool does and also fit in the palm of your hand. It can be slipped into your pocket.
The longer you use this tool to maintain your knives the more the edges become "matched Up" with the sharpener itself, to where you know a given kitchen knife is a 10 dps or your favorite EDC is a 24 inclusive. Just set the scale at the corresponding angle and sharpen.
I've been sharpening and making knives for 17 years and can put an edge on most anything metal, with a lot of different techniques and using different devices; my favorite device is the ERU; it does so many things well.
Micro bevels in minute increments, edge alignment, ascertaining existing edge angles, removing wire edges or keeping your knife edge sharp in the field.
Each one of these is made by my son and I in our shop in S/E Ohio. We do the machining, anodizing and finishing. Each ERU is fitted by hand the carbides are set and epoxied by hand, lapped and trued by hand and the sheaths, until I can afford a stitching machine, are sewed by hand.
Once that machete is sharp, the ERU will keep it working.
Fred
That's what I really needed to know, thanks Mr. Rowe. Still might try to pick one up in future. I'm always on the lookout to add touch up tools to my primary DMT diamond stone equipment.
- Joined
- Jul 1, 2013
- Messages
- 32,479
No! No! No!
These machines are terrible! The take off way to much metal and produce too much heat.
A place down the street from me uses one of those to sharpen knives for customers. The people that get them done there then come to me to get there knives rescued! Sometimes I can, and sometimes not.
- Joined
- Mar 31, 2011
- Messages
- 3,005
WSKTS.
Be sure to get some quality aftermarket belts, and use very light pressure - especially as you approach the tip.
I've used mine to quickly get, and maintain, razor sharp edges on a multitude of steels: German kitchen steel, 8CR13, 154CM, S30V, D2, M4, M390, SR101, ELMAX, INFI, others. Haven't used in on my CTS-XHP yet, but I will when the time comes. I don't currently have anything in ZDP-189, S90V or S110V but I wouldn't hesitate to sharpen them with it with the right progression of belts.
Be sure to get some quality aftermarket belts, and use very light pressure - especially as you approach the tip.
I've used mine to quickly get, and maintain, razor sharp edges on a multitude of steels: German kitchen steel, 8CR13, 154CM, S30V, D2, M4, M390, SR101, ELMAX, INFI, others. Haven't used in on my CTS-XHP yet, but I will when the time comes. I don't currently have anything in ZDP-189, S90V or S110V but I wouldn't hesitate to sharpen them with it with the right progression of belts.
Last edited:
I don't like pull through sharpeners, for the reasons that others have given, i.e., removing too much metal. Consider also that when you use one, the scratch pattern will be parallel to the edge rather than perpendicular to it. That will weaken the edge as well.
- Joined
- May 2, 2004
- Messages
- 6,848
If you have used all pull through sharpeners you can make that statement with some assurance. But I don't believe you have used the ERU; which suffers from neither of these issues. It neither removes too much metal or does it leave a scratch pattern running parallel to the edge. Being a knife maker myself I would think in order to "weaken" the edge of a blade the scratch pattern would have to be somewhat visible at least under a decent loop; such as those deep scratches that can cause stress fractures. The ERU leaves a polished edge with little scratch pattern at all.
Carrying that line of thought further; a scratch pattern running at 90 degrees to the edge would weaken an edge as well; and I don't believe thats the case.
What can weaken an edge is poor geometry along with inferior heat treatment. An edge is more prone to breakage or chipping when its either to hard for the geometry or to soft for the geometry used in designing and making the knife.
Stress fractures, where a blade will break along a visible and abrupt angle change, or one that is created during heat treat, which is not visible. The ones that come during heat treat can be from numerous factors.
Your points are not out of place and have been valid for years; but things change, they do not stay the same; progress and our inventive nature move us forward.
Regards,Fred
- Joined
- May 2, 2004
- Messages
- 6,848
The Knoop scale is a bit misleading when it comes to this comparison. This scale is normally used when testing brittle materials, such as quenched vanadium and not carbides that have been tempered. If the two are looked at using the Mohs scale they appear to be much closer in hardness, vanadium carbide @ 9.5 and tungsten carbide @ 9.0 at least their basic structure.
Something else to consider is all carbides in a knife blade are contained within an iron matrix which has been hardened and then tempered; whereas the tungsten carbides used in sharpeners are bound with cobalt, the percentage of the mixture dictating how hard and how tough the material.
Considering the variables will make the discussion more relative.
What do you think; does this sound reasonable?
The reason I bring this up is I've had several reports from people who used the ERU with good success on Elmax as well as M4, both containing vanadium carbides.
Fred
- Joined
- Apr 12, 2009
- Messages
- 13,209
The thing I've never liked about the Moh's scale is that it's completely unitless. It's an ordinal scale, indicating only where each material stands in relation to the others above and below it, essentially like the finishing order in a race ('First Place' thru 'Last Place'), with no indication of how 'fast' each participant actually ran. The 'values' assigned to each material within it are essentially arbitrary as a result, and each positional 'value' only represents that a given material is able to scratch the 'softer' material below it, and unable to scratch the 'harder' material above it. If or when new materials are 'fitted' into the list, a fractional number (such as '9.2') is given to place it in the appropriate order within the list.
( Text below quoted from the Wiki article on 'Mohs scale of mineral hardness', found here: http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness )
The Knoop or Vickers scales actually represent measurable quantities, in determining how much pressure (lbs/inch[SUP]2[/SUP], or kg/mm[SUP]2[/SUP], for example) must be applied to produce an indentation in the tested material, to a given depth and/or cross-sectional area, using an indenter of fixed shape and known hardness (such as diamond) as the reference. This is why either Knoop or Vickers (and any others using actual measured units and comparing to known fixed standards) will always be much more accurate, and truly representative of the forces and physical properties involved in abrasion (scratching a material using another; how much hardness and pressure will produce scratches of a given depth in a material).
So, with respect, I'd say the Moh's scale is the most misleading of any, in terms of describing exactly how hard a material really is, because it measures absolutely nothing, literally.
David
( Text below quoted from the Wiki article on 'Mohs scale of mineral hardness', found here: http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness )
The Knoop or Vickers scales actually represent measurable quantities, in determining how much pressure (lbs/inch[SUP]2[/SUP], or kg/mm[SUP]2[/SUP], for example) must be applied to produce an indentation in the tested material, to a given depth and/or cross-sectional area, using an indenter of fixed shape and known hardness (such as diamond) as the reference. This is why either Knoop or Vickers (and any others using actual measured units and comparing to known fixed standards) will always be much more accurate, and truly representative of the forces and physical properties involved in abrasion (scratching a material using another; how much hardness and pressure will produce scratches of a given depth in a material).
So, with respect, I'd say the Moh's scale is the most misleading of any, in terms of describing exactly how hard a material really is, because it measures absolutely nothing, literally.
David
- Joined
- May 2, 2004
- Messages
- 6,848
David,
That helps in understanding the difference between the different scales.
What are your thoughts on the hardened and then tempered factors in judging the difference? I understand this as a knife maker with hardness after quench and then the hardness after temper being different. Time at temperature in other words. What is the relationship between the two when it comes to vanadium carbides relative to the sintered tungsten carbide?
Fred
That helps in understanding the difference between the different scales.
What are your thoughts on the hardened and then tempered factors in judging the difference? I understand this as a knife maker with hardness after quench and then the hardness after temper being different. Time at temperature in other words. What is the relationship between the two when it comes to vanadium carbides relative to the sintered tungsten carbide?
Fred
- Joined
- May 2, 2004
- Messages
- 6,848
I ask someone who knows the subject far better than I and here is his response. It helped me see the relationship much better. I tend to think to large and with carbides and steel structures you must think small.
Fred, I know it seems quite small but on the scale of carbides the HRC test dimple is huge, too big to measure the individual carbides. What the Rockwell test measures is the overall matrix of the steel. This topic touches well on the analogy I use often in my classes of a doughy ball of clay filled with small chunks of glass. If you skate a file over the ball of clay the tops of the chunks of glass will give you the impression that the entire ball is as hard as glass. If you take the handle off the file and plunge the tang into the ball, the glass chunks will just push aside and you will see that the ball is as soft as clay. This is the difference between Rockwell tests and skating a file. Hardness is actually not a property of steel as much is it is a way of us conceptualizing or quantifying other real properties. Scratch tests like the Mohs scale and files measure the property of abrasion resistance; Rockwell measures the property of strength.
So lets start out with1080 steel. At room temperature it is pearlitic, a phase consisting of alternating bands (lamellae) of ferrite (soft iron) and cementite (very hard iron carbide). A Rockwell test will simply bury the needle into the ferrite, pushing the cementite aside as it goes. The reading will probably be HRC 32 or less. The matrix itself is not strong because the carbon is trapped in the carbide and not reinforcing the iron. But if we heat the steel up and dissolve the carbide to mix its carbon into the ferrite, and then quench it, the overall matrix will then resist the penetrator to give us a reading of 65 HRC.
Now lets do some magic forging techniques that has been fantasized about over the years and add carbon to our 1080 until it is 1095. Pretty much all the same behavior will apply until we quench it, then we will get the same HRC readings there as well, but there will be all these extra iron carbides that are even finer than the pearlite lamellae and push aside all the easier. They contribute even less to the overall Rockwell reading, but push the abrasion resistance via scratch hardness much higher.
Adding chrome, tungsten or vanadium to the mix will increase the number of carbides formed because these elements like the carbon even more than iron does. So you must be careful not to put so many in that they use up all the free carbon and limit your maximum Rockwell hardness by robbing the matrix of carbon. These carbide will be more complex and much harder so even more abrasion resistant, but they still are too small to have an effect on the HRC value.
If you take your piece of steel, and put it under a Vickers or Knoop type micro-hardness tester, which is more like a microscope with a microscopic penetrator built in, your Rockwell dimple will look like Meteor Crater in Arizona. But if you polished a section next to it to reveal carbides and the carbides were huge, you may be able to drop the micro-hardness penetrator on one and get a reading of equivalent to 70, 80 or even 90 HRC, even though the steel itself is giving an overall Rockwell reading of only 65.
While tempering decreases the HRC reading of the steel by taking carbon out of the matrix, it actually increase the carbide numbers as it uses the freed carbon to make ultrafine tempering carbides, which you would never measure the hardness of, even with a micro-hardness tester, because they are so fine to see with anything short of an electron microscope.
So in the end you have the two concepts of hardness discussed here- scratch hardness, or abrasion resistance, and penetrative hardness or overall strength. Carbon that free to reinforce the steel matrix increases overall strength as read by the Rockwell tester, while carbon locked in the form of carbide which contributes little to overall strength, and thus is not measured by the Rockwell test, but increases abrasion resistance, so it will eat up files, mills and even challenge abrasives (ask anybody who has hand polished Cru-forgeV how pleasant it was).
Fred, I know it seems quite small but on the scale of carbides the HRC test dimple is huge, too big to measure the individual carbides. What the Rockwell test measures is the overall matrix of the steel. This topic touches well on the analogy I use often in my classes of a doughy ball of clay filled with small chunks of glass. If you skate a file over the ball of clay the tops of the chunks of glass will give you the impression that the entire ball is as hard as glass. If you take the handle off the file and plunge the tang into the ball, the glass chunks will just push aside and you will see that the ball is as soft as clay. This is the difference between Rockwell tests and skating a file. Hardness is actually not a property of steel as much is it is a way of us conceptualizing or quantifying other real properties. Scratch tests like the Mohs scale and files measure the property of abrasion resistance; Rockwell measures the property of strength.
So lets start out with1080 steel. At room temperature it is pearlitic, a phase consisting of alternating bands (lamellae) of ferrite (soft iron) and cementite (very hard iron carbide). A Rockwell test will simply bury the needle into the ferrite, pushing the cementite aside as it goes. The reading will probably be HRC 32 or less. The matrix itself is not strong because the carbon is trapped in the carbide and not reinforcing the iron. But if we heat the steel up and dissolve the carbide to mix its carbon into the ferrite, and then quench it, the overall matrix will then resist the penetrator to give us a reading of 65 HRC.
Now lets do some magic forging techniques that has been fantasized about over the years and add carbon to our 1080 until it is 1095. Pretty much all the same behavior will apply until we quench it, then we will get the same HRC readings there as well, but there will be all these extra iron carbides that are even finer than the pearlite lamellae and push aside all the easier. They contribute even less to the overall Rockwell reading, but push the abrasion resistance via scratch hardness much higher.
Adding chrome, tungsten or vanadium to the mix will increase the number of carbides formed because these elements like the carbon even more than iron does. So you must be careful not to put so many in that they use up all the free carbon and limit your maximum Rockwell hardness by robbing the matrix of carbon. These carbide will be more complex and much harder so even more abrasion resistant, but they still are too small to have an effect on the HRC value.
If you take your piece of steel, and put it under a Vickers or Knoop type micro-hardness tester, which is more like a microscope with a microscopic penetrator built in, your Rockwell dimple will look like Meteor Crater in Arizona. But if you polished a section next to it to reveal carbides and the carbides were huge, you may be able to drop the micro-hardness penetrator on one and get a reading of equivalent to 70, 80 or even 90 HRC, even though the steel itself is giving an overall Rockwell reading of only 65.
While tempering decreases the HRC reading of the steel by taking carbon out of the matrix, it actually increase the carbide numbers as it uses the freed carbon to make ultrafine tempering carbides, which you would never measure the hardness of, even with a micro-hardness tester, because they are so fine to see with anything short of an electron microscope.
So in the end you have the two concepts of hardness discussed here- scratch hardness, or abrasion resistance, and penetrative hardness or overall strength. Carbon that free to reinforce the steel matrix increases overall strength as read by the Rockwell tester, while carbon locked in the form of carbide which contributes little to overall strength, and thus is not measured by the Rockwell test, but increases abrasion resistance, so it will eat up files, mills and even challenge abrasives (ask anybody who has hand polished Cru-forgeV how pleasant it was).
- Joined
- Jul 1, 2013
- Messages
- 32,479
Bo,
I am a custom knife maker & sharpener by trade, I recently evaluated Freds ERU for about two weeks at my shop. Just so you know I did this because I was interested in Fred's system and we know each other from Knifedogs for a few years. I have no monetary gain in Fred;s ERU.
For the 20 plus years as a profession and before as a Cook and outdoors man I have tried most every gadget Gizmo with carbide inserts and they are all mediocre at best and usually very damaging as other have stated.
Then I used Fred's ERU. I sharpened knives of my own and production blades of CM154, 440C, CPM-S30V CPM-S35VN, 1095, O1, VG-10, VG-5, VG-1 and David Boye's Detentric 440C that has huge carbides in it plus many mystery steels.
This unit can be used on ALL steels! Use a black marker to get your exact angle.
For the field it is the best sharpener of its size and configuration I have ever used.
For the home, I recommend putting in a vice for people like your wife and other folks that are not sharpening aficionados. Its a little small to hold onto and my own wife would not be comfortable pulling a large kitchen knife through the ERU without it being held in a vise..
- Joined
- Apr 12, 2009
- Messages
- 13,209
For some time, I've been looking (& looking, & looking) for some published info regarding how the hardness of vanadium carbides (individually) may or may not change by heat treat. The only vague reference I remember seeing, was a mention that the hardness of VC is essentially inherent from it's manufacture in the given steel, and whatever changes might occur with heat treat later on don't seem to impact it significantly. The exception comes at extremely high temperatures (upwards of something like ~800°F or higher), where hardness drops off a cliff, as with most materials, when heated to extremes. I was doing more looking around & reading last night (my eyes HURT today; combination of too much reading and not enough shut-eye), and I've seen Vickers hardness values for Tungsten Carbide specified as a range, from something like 1700 up through maybe 2400 (I'm assuming hardenability by heat treat or other processes, but I don't know). Comparing that to published Vickers hardness values for vanadium carbides, I've only ever seen values listed specifically, something like Vickers ~2800 or so (though some are reporting it much higher, up to 3800; diamond is assigned a value of 10,000 at the top of the Vickers scale, for reference). And the one thing that continually sticks in my memory, is that I've never seen VC listed at equal or lesser hardness as compared to WC (tungsten carbide). When compared side-by-side in the same listing/ranking, the VC always lists as being harder than the upper limit of the ranges measured for WC.
Still reading some more today; I like and appreciate your later post (#32), and it seems to make sense to me, regarding the need to use 'micro'-scale testing methods for measuring the much-harder carbides within a steel matrix.
David
Last edited:
Laurence,
Thank you for the information. I have a friend who is at a complete loss when it comes to sharpening. This tool is the ideal gift for him. And it will save me the agony of having to sharpen his pocket knife after watching him (literally) tear through a trout when trying to clean it.
Thank you for the information. I have a friend who is at a complete loss when it comes to sharpening. This tool is the ideal gift for him. And it will save me the agony of having to sharpen his pocket knife after watching him (literally) tear through a trout when trying to clean it.
- Joined
- Dec 16, 2012
- Messages
- 4,437
Something like the ERU and something like the Sharpmaker should make a great pair. To use the ERU you need the angle of the edge. Most clamp systems can't adjust for width of blade and lead to skewed results. Unfortunately if you can't sharpen the knives with a precision system the ERU will be either useless or an annoying system of trial and error (unless you want to just sharpen them acute once and just micro bevel the knives).
The ERU is definitely an item to watch, and it is poised to redefine the pull though sharpener and carbide plates for sharpening in general.
BluntCut MetalWorks
Knifemaker / Craftsman / Service Provider
- Joined
- Apr 28, 2012
- Messages
- 3,431
Adaptable angle is one of ERU strength, it's carbide inserts adapt (by closing up the insert) to whatever the knife cutting bevel angle. It's a touch up sharpener, so you would need something else for back bevel (non-cutting-bevel/micro-bevel).
- Joined
- Jul 1, 2013
- Messages
- 32,479
For all of B & T and Fillet knives I tried, Fred's ERU is perfect for refining an edge for meats & fish while in the field.
There were two different grit ERU's one at 320 and one at 600 grit. For the vast majority of field work the 320 g I felt would be more than adequate and if you had small distortions or chips you could get them out with a little work.
I think my friend has some problems with fine motor control and I don't have any issues with cleaning up the primary bevels on a couple of Moras that I gave him or sharpening his pocket knife, when I have a nice bench stone or similar available. For the other 99+% of the time the ERU seems ideal.
Fred,
Post a link or PM me when more information becomes available. Thanks.
Fred,
Post a link or PM me when more information becomes available. Thanks.