MYTHS ABOUT KNIFE EDGES

[htr]

Now to sharpness levels. There are those who claim to sharpen straight edges, using traditional methods, to modern day DE razor blade levels but several experienced straight edge sharpeners say, no, they can't. Our all time best here in the shop, using modern methods, is 65 and that number has never been repeated since. We know that our instruments have been used by customers to measure straight edges but apparently, mostly under the cover of darkness with curtains drawn tight. To this day, we have never had a straight edge sharpener report sharpness levels to us. Most every other kind and sort of cutting/slicing/shearing edge, yes...but never a straight edge razor.

I recently bought the PT50 and this is the first time I have tested my straight razors.
I have 2 that are initially sharpened on shapton glass stones. Both got decent BESS number when stropping on balsa with 1 micron Boron Carbide and then 0.5 micron chromium oxide and finally finished on a Kanayama Cordovan Strop.
Here are the numbers: after shaving (Before stropping) 66 BESS and after stropping 27 BESS.
The vintage razor finished at 17 BESS.

Links to small videos:
Razor 1 before stropping
Razor 1 after stropping
Vintage razor after stropping

Kind regards
HTR

[EOU]

Well just how cool is that HTR?! Welcome to the BESS Exchange and thank you for providing information that we have been looking forward to for a very long time. So now we know. Not only can straight razor edges be sharpened "as sharp" as a standard DE blade but even sharper than a Feather razor blade. 

We've also have a sneaking suspicion that this wasn't the first straight razor edge that you've sharpened. No "after dark" and "curtains pulled tight" for you. You obviously know what you're doing. 17 isn't far off of microtome numbers. Isn't it interesting that these edges can roll to the degree your's did after shaving and then be brought right back with a piece of leather? Now we know why those old barber shop strops were attached right to the side of the chair. 

Can't thank you enough HTR and hope that you are able to bring us more in the future.

P.S. Does this mean that you're not overly impressed with our 65?

[htr]

Sorry I am not an expert on straight razors. I tried to learn how to use it and how to sharpen it about 8 years ago. This is the first time I use it in 5 years.
To be honest I am a little afraid to use it so I finish shaving "difficult" places like under the nose and under the chin with a DE safety razor. One small mistake with the straight razor and you learn how sharp it is....   

Maybe I was lucky to get low BESS numbers. I will shave with the vintage razor later today and see what numbers I get then.
Maybe I use the PT50 wrong, e.g. too high tension on the test wire give me low readings?

I don't use any fancy equipment or technique, I have this Balsa strop kit with two balsa plates loaded with 1 micron Boron Carbide and 0.5 micron chromium oxide.
This is similar to the horse butt strop I have: Kanayama Cordovan #50000 Razor Strop , mine was a special order but it looks identical to the one in the link.

I promise to do the new test before its "dark" and open the "curtains"      I am happy to share information.
If I am able to replicate the BESS numbers then we could create new straight razor thread, if my numbers and test technique turn out to be a myth then we keep them here  

Cheers,
HTR

[htr]

Here are the BESS scores for the vintage razor with links to videos:
BESS 17 yesterday, I did not test today before I started shaving.
BESS 41 after shaving 50% of the face, I chickened out and finished with a DE safety razor    (video: vintage after shave ) 
BESS 33 after stropping 5 times each side on Kanayama Cordovan Strop (Video: vintage after stop )
BESS 19 after stropping 10 times each side on balsa with 0.5 micron chromium oxide and finally finished on a Kanayama Cordovan Strop 5 times each side. (Video: final stropping )

Please be advised that this is only my trial and error (or trial and success) for this razor and might or might not work for other razors.

Cheers
HTR

[EOU]

"Sorry I am not an expert on straight razors." 

You may not be HTR but in our opinion you're an expert sharpener of straight edge razors. You just have to realize that there simply isn't much room left for improvement after a 17 and a 19. We really wonder if you aren't bumping up against the physical limits, in consideration of the steel and blade geometry, of how sharp a straight razor can become.

We notice that most straight razor guys recommend stropping immediately before use. No one says "why" immediately before use but our money is on removal of any accumulated oxidation and/or straightening out any effects of residual metal memory. Our best bet says that tomorrow, your 19 won't be 19 any longer but if you then strop, it very likely will be. 

We're not trying to encourage further shaving experiments with the lethal weapon you've developed  but if you have plans to do so, would recommend that you first have a nice photo taken so that we can all be reminded of how handsome you used to be.

Thanks very much HTR, again, for your reports!

[KnifeGrinders]

Since this is the first straight razor owner report on BESS scores, I second the HTR that we better copy the straight razor related posts from this thread to a dedicated thread in the BESS section of this forum.

We keep hearing from the straight razor users that their cutthroat razors shave better than factory DE safety razors.
A thorough investigation of that subjective feeling was done by Todd Simpson https://scienceofsharp.wordpress.com
Todd, professional in SEM microscopy, gave edge apex width for Feather, Gillette, Wilkinson, Kai, and Derby DE razors, and has shown that honed staight razors can have smaller edge apex radius.
When I asked Todd, he said he had to break off a segment of the straight razor for it to fit the SEM.

Exhaustive investigation of BESS scores for DE safety razors was done by Chase Anderson https://www.refinedshave.com

HTR is the first ever who tells us of BESS scores for straight razors.

@HTR - just one clarification please - in your final honing step, do you use the Kanayama Cordovan Strop without any polishing compound?

[htr]

@HTR - just one clarification please - in your final honing step, do you use the Kanayama Cordovan Strop without any polishing compound?

Final honing is without any polishing compound.

[Bud]

 I chickened out and finished with a DE safety razor 


That's a good one HTR and made me chuckle. Do you have to switch hands when shaving one side of the face or the other? I don't think I'd trust either my left or my right so if you got even one side done you're a braver man than me. Great BESS scores by the way.

[KnifeGrinders]

Common Misconceptions About Knife Edges



Myth – The best edge angle is 40-50° for chopping, 30-40° for cutting, and 20° included for slicing


Source: Tormek handbook

The truth is that the best is the thinnest possible edge for the cutting task.
The antique wootz swords in my collection that still have a battle-ready sharp edge show around 18-20 degrees included on a laser protractor.
Japanese katanas edge is 16-18 degrees included.
For the best performance the knife edge must have the lowest angle its steel can hold; give your edge the least possible angle not over-thinning the edge past the angle at which it deforms in cutting the stuff you intend to cut.
This has been proved by Cliff Stamp (http://cliffstamp.com/knives), by our BESS-SET experiments on edge rolling in mainstream knives (http://knifeGrinders.com.au), and by CATRA tests on high-end steels done by Larrin Thomas (http://knifesteelnerds.com).

Myth - Obtuse edge angle has longer edge retention
Some have also speculated that lower angle edges start out sharper but a more obtuse edge lasts longer, and that reducing edge angles decreases the cutting lifetime.

Reality is that smaller angle stays considerably sharper and the difference holds to the end of the CATRA and BESS-SET tests on mainstream and super steels.
Take for example well-hardened felling axes – they are sharpened at 25° included and sharp enough to shave with. The only situation where the obtuse angle wins is when the knife is used to open tin-cans.

Myth – Too fine an edge dulls quicker
A common misbelief is that sharpening past a certain point is useless since the edge that is too sharp will dull fast.
 
Truth – For better cutting performance, the edge should always be sharpened to the sharpest apex you can.
Experiments have shown that the best cutting performance through the test have knives with the best initial sharpness.
Sharp apex does not predispose the edge to rolling - over-thinning the edge past the angle at which it deforms in cutting certain stuff does.
Try to visualize the rolled edge with your mental vision, see this edge bend and the sharp apex at the bend end - the stuff it cuts wraps over the bend until it contacts the edge apex where it is severed; when the apex is sharper even the rolled edge cuts better. In other words, the sharper edge mitigates edge rolling.

Myth - Coarse edge cuts better



The "micro-serrations" concept contributes to the confusion as people tend to generalise properties of the serrated edge onto the microscopic level of a ragged coarse edge.
A coarser edge does slice better initially due to "micro-serrations", however the coarse finish is associated with increased grip force, cutting effort and cutting time, and worse edge retention – the knife dulls faster as the "teeth" get broken off or bent to one side or the other. In precise cutting and carving unpolished bevels cause traction in cuts and lower accuracy and quality of cut.

Myth – Convex grind aids in edge retention
Reasoning is that the edge apex needs enough "meat" to last, and the edge will dull quicker where there is not enough metal behind it to give it strength.


Source: Bark River Knife Collector's Association

Truth - Stump splitting and bone chopping are the only tasks where the convex edge is advantageous. Other than for meat cleavers, splitting axes and machetes and larger camping knives used for splitting, the optimal edge is not convex. Those blades don't work as well with a hollow grind because the shape of the bevel "stops" the force of the stroke, and it also does not provide the same support for the edge subjected to a serious impact.


For those kind of blades it is the go, but for most other every day applications the convex edge is less than ideal. Yet "survivalists" would argue that if left with only one knife, the convex edge is superior - if I were left to survive in the woods, I’d rather have a hollow-grind knife and a hatchet.

Myth - Super steels hold super-sharp edge



Truth - The initial blunting rate is relatively rapid regardless of steel. The high-end wear-resistant edge sharpness quickly moves beyond the shaving range to just sharp. Though wear-resistant edges win in the long run, they lose their initial keenness almost at the same rate as a mainstream knife. High-end knives win over mainstream as stayers, but they are equal sprinters.
We’ve seen this in both in our BESS-SET tests and CATRA tests done by Larrin Thomas, let alone the real life.

Myth – knife manufacturers sharpen at an angle optimized for the best performance


Source: Zwilling J.A. Henckels

Actually, where the knife comes with a warranty, the manufacturer applies the edge angle which will make repair returns as unlikely as possible - in other words the factory edge is optimised for abuse, not cutting.
Where there is no clear replacement policy, the edge angle can be anything no matter what the knife purpose is. We’ve checked edge angles on slicing, filleting, carving, sticking and boning knives made by leading professional knife manufacturers – any of these knives could have any angle: 30, 32, 34, 36, 38, or 40° included, seemingly regardless to the knife function; the voluntary ignorance we’ve seen is almost flabbergasting.
It is normal for knives with distal taper to have edge angle slightly increasing from the heel to the tip to maintain a uniform bevel - however hardly we can call it "normal" when we see an edge angle on one side higher than on the other on a production knife. In the few manufacturers’ videos on YouTube and Instagram knives are sharpened freehand, with no angle guides.

Myth - Cheap knives are easier to sharpen


By courtesy of Lewis Hilsenteger, Canada

Every so often I run across a customer asking for a discount on sharpening his junk knives, motivating that the knives cost him less than would sharpening. Video gamers "collectible" knives are also in this category.
True that those inferior steels are easier to grind, but that shiny stainless steel is a pain to deburr - getting rid of the gnarly burr these cheapo knives usually produce is so difficult that you can clean the edge apex only at the cost of rounding it.
In response to your efforts the highly malleable burr just keeps bending back and forth and bending and bending like a foil leaf. To get rid of this crud of metal you take a higher and higher angle, gradually realizing that in the process of removing the existing burr you're also drawing new metal out past the apex and creating a new burr – the reason people call it mutant burr and burrZilla.
There are times when you think you’ve succeeded, yet under a good light you still can see remnants of the burr. Overall, sharpening junk knives can be extremely frustrating unless you know a method to abrade the burr away faster than a new burr is created.

Myth - Japanese knives must be sharpened on Japanese waterstones



The demand for natural Japanese sharpening stones comes mainly from the traditional sword polishers, while chefs prefer synthetic stones. The Japanese synthetic stones are made of the same common abrasives used elsewhere outside Japan like aluminium oxide, silicon carbide and chromium oxide; what makes them Japanese waterstones is the technology of fusing the abrasive particles in a porous matrix – but even this is becoming history. Nowadays less and less Japanese synthetic stones require soaking in water for use, and more and more resemble non-Japanese sharpening bench stones that should be stored dry and used with just a splash of water on the surface.

Myth – Finer abrasive grit correlates  with sharper edges



There is no clear correlation between the abrasive grit rating and apex width you get on it. For example, you can produce an edge apex in the safety razor range of 0.1 micron on a 300 grit abrasive, though with a significant variation in the apex width along the edge.
Factory edges never come polished, and when they are sharp they are the best proof that edges don't need a fine scratch pattern, let alone polished finish, to be scary sharp.
However, in refining the sharp edge the honing compound grit size and the scratch size are related by about an order of magnitude, e.g. honing/stropping with a 0.5 micron abrasive refines your edge finish to 0.05 micron.
Fine grits are used is to improve the edge finish and keenness for effortless cutting, but not the sharpness as such; a more refined edge also holds up better.

Myth – Mirror edge is not worth the effort
Someone called mirror finish "a labor of love". One look is worth a thousand words -


Milla Jovovich photo by Chris Floyd


When I sharpened this Santoku for an Australian knifemaker Snake & Rabbit Knives I mirror polished the 8 dps edge to match the rest of the blade. The photo is unedited, taken in daylight - the mirror finish is so perfect that the blade blends with the reflection like a stealth.

[Jan]

Congrats Mr. KG to an interesting article in the Australian Knife journal.

Jan