Bevel Angle and Effect on Shaving for a Newbie
- Thread starter rbscebu
- Start date
Yeah, it's just my inability to make nice modifications to a photo. The right way is to measure along the line as shown on the screenshot. Saying that I tried both, and because the difference is so small the answer came out exactly the same, to one decimal point.
What I tried to show was just that you can take the measurements off a photo without the need for a Vernier and get an result that is accurate enough for our purposes.
Thank you. I am glad that you did that
because I have found it difficult to measure the razors directly.
I did the calculation from a photo that @Ice-Man posted and I was surprised at the result.
www.badgerandblade.com
From the photo it looks like the Koraat has a bevel angle around 20 degrees without considering honing with tape. I would have expected a lot less, but that confirms what @str8six posted on that thread about Koraat.
Koraat Opinions
Hello all: I'm new here, so I'm interested in your opinions. I realise that my question could be one of those "kill the messenger" things....but I would appreciate if you can bear in mind, I'm just asking a question. I recently ordered a Boker Feldmann, and was contacted by the owner of the...
www.badgerandblade.com
From the photo it looks like the Koraat has a bevel angle around 20 degrees without considering honing with tape. I would have expected a lot less, but that confirms what @str8six posted on that thread about Koraat.
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- Thread starter
- #25
rbscebu
Girls call me Makaluod
A sharpie test will tell you if it has been honed with tape.I did the calculation from a photo that @Ice-Man posted and I was surprised at the result.
Koraat Opinions
Hello all: I'm new here, so I'm interested in your opinions. I realise that my question could be one of those "kill the messenger" things....but I would appreciate if you can bear in mind, I'm just asking a question. I recently ordered a Boker Feldmann, and was contacted by the owner of the...
From the photo it looks like the Koraat has a bevel angle around 20 degrees without considering honing with tape. I would have expected a lot less, but that confirms what @str8six posted on that thread about Koraat.
Koraat hone all their razors with a single layer of tape, unless you specifically ask them not to. I bought mine from a member and the first thing I did was to set the bevel without tape. You know...... balsa strops and tape don't mix.
Slash McCoy
I freehand dog rockets
Actually, no, you can't, with any proven reliability. It is a matter of perspective.
Tape a sheet of graph paper to the wall. Take your cel phone and take a picture of it. Compare the vertical edge of the pic with the vertical lines of the graph paper and the edge of the graph paper. Compare the horizontal borders, top and bottom, with the top and bottom edges of the graph paper and the horizontal lines. Unless you are extremely meticulous, you will see that up and down isn't necessarily up and down anymore. The width of one square or 10 squares or whatever isn't necessarily the same everywhere on the picture. Relying on a photograph for measurement and calculation is imprecise unless you take measures to ensure precision, which are no easier and no simpler than simply measuring accurately in the first place with common ordinary measuring instruments like a cheap plastic vernier scale or dial caliper.
With a good tripod, try to photograph the graph paper with all four edges aligned exactly to the edge of the image. Now, with mechanical assistance, you can achieve much better results. BUT... are the edges straight? If the left top corner of the paper is at pixel (3,3) and the bottom left corner is at (3,637) then you got it nice and vertical, but at the midpoint of the left edge, is the edge of the paper exactly at (3,320)? Or is it bowed in or out a bit? Check the top and bottom edges in the same manner. The sphericality of the lense comes into play. And this, with the camera solidly held in a tripod.
There is also a question of the contrast and lighting in the pic. The pic of the razor you want to measure, that is. Someone who knows a lot more than I do, about light and shadow and composition and digital photography in general, would have to comment on that.
Nobody is stopping you, and maybe your results are accurate enough for your purposes. The thing is, you cannot verify the accuracy or that such a level of accuracy is within your tolerance without resorting to actual physical measurement, one way or the other.
There IS a shortcut, once you actually have measured quite a few razors, and that is to simply eyeball the razor in question and estimate. You might be surprised to find that it becomes easy to eyeball it to within a degree, possibly to within the nearest half degree. More? I make no such claims for myself but it would not surprise me if someone could achieve quarter degree accuracy with a reasonable rate of success. And, it just so happens that a half degree is probably about where the difference in the shave becomes readily detectable. Less than a half degree is of little consequence and so half degree accuracy is "good enough" for most of us. BUT... is your photoanalysis of a razor going to be even that accurate, with any reliability? Maybe. But how do you know?
Yes, and no. It probably has to do with how much flex there is in the blade, but I successfully methodized my Herder without any trouble, and it had been honed on tape. Granted, it's over 7/8 and thin. That experiment has failed on smaller, stiffer blades.
Agree that photos have lens distortion in them, don't agree it makes a huge difference.
I do have a digital Vernier calliper, and I question the accuracy of my measurements on it. Spine thickness is the easy part, but when it comes to the part when you have to measure the width, I have a few issues. I don't want to touch the edge with the metal Vernier, and when you have some hone wear it is difficult to see exactly where the furthest to the edge part of the hone wear is. Shiny surfaces play havoc with my eyes, even with the reading glasses on. With the Vernier it's a close guestimate, +/- .5mm not 100%.
Does it matter to me? Not at all. A difference of 1/10th of a degree is not going to make me dump a razor in the bin for not meeting my preferred bevel angle.
My only interest is to see if the razors I enjoy using from experience have a similarity, like I have found with thin grinds.
Easy enough to test, send me a pic of a razor for which you know the bevel angle and let's see if I can get it right.
Don't even go there, someone nearly bit my head off for making a similar statement!
Slash McCoy
I freehand dog rockets
It's not just the lens distortion. There is also perspective. Making the focal plane of the camera exactly parallel to the desired image plane, and that desired image plane being correct and relevant to the desired measurement. And the lighting and shadow which determines what pixel will be selected for end points of measured lines. For this to work, every blade would have to be photographed at exactly the same angle and with lighting from exactly the same angle. The camera is easily fooled and the eye is easily fooled. I don't like digital dial calipers and I have never seen a digital vernier caliper. I don't know what that is. Most cheap vernier scales are plastic and if used VERY carefully, won't cause more damage than can be stropped away. Because the hypotenuse is the long measurement, it is less dependent on accuracy than the opposite measurement, which is half the spine thickness, essentially. The spine thickness I measure with a dial (not digital) caliper because being the shortest measurement, accuracy is important, and being not at all fragile, metal tools are not a particular hazard to it.
I agree, a tenth degree is of no particular importance. But do you know that your typical error from reading a random photograph of a razor is only a tenth of a degree? If it can't be quantified, then it isn't relevant data. And if test conditions are not controlled and consistent, it can't be properly quantified. Use of measuring tools is as precise as the tools are and the hand and eye of the user are, and are totally under the control of the user of the tools and of the data. I find magnification to be of help in taking certain measurements in certain conditions, by the way. My eyes are 62 years past the issue date so I feel you on the eye havoc. But unless you yourself take the pictures with the razor aligned the same and lit the same every time, you have a lot of wild cards there. Anyway, said my piece, that's all I got.
These ones are supposedly vernier calipers. Larger scale on the ruler part and smaller scale on the digital reading.
Appreciate your input, like always, that’s why we are here, to share opinions. It will be a sad day when everyone agrees!
Appreciate your input, like always, that’s why we are here, to share opinions. It will be a sad day when everyone agrees!
If all other things are equal then yes, this is certainly the case.
Slightly geeky post I did about it here:
Knife Sharpening Thread - https://www.badgerandblade.com/forum/threads/knife-sharpening-thread.613571/post-11474789
Slash McCoy
I freehand dog rockets
I do think a slightly beefy bevel angle is good for a beginner, but I don't think it should be the major criteria in shopping for a first razor. After all, when is the last time you saw a razor vendor or maker listing the bevel angle? If it is known, then it is worth considering. The beginner might want to shy away from a very acute sports car of a razor, but anything of average to slightly fatter than average will do, in that regard. I think there are other things more important, like how ergonomic a razor is, or how well it fits the hand and naturally finds the face. Honestly, just getting a plain, average, mainstream, not extreme in any way, razor, for a good price, with a good edge on it, should be the goal. Departing in any way from the norm should only be done when the beginner is a few dozen shaves in, and wants to try something a little different, in order to find out what his preferences will be. That "something different" might be a wider razor, or a more smiley or a straighter razor, or an extra hollow or a full wedge, or a very acute bevel angle. Or a custom, or a top shelf high quality razor, or a very very cheap one.
A thoughtful seller might select a razor over 17 degrees for a newbie looking to buy his first razor, though, if he normally notices things like bevel angle. Lots of guys just don't pay any attention to it and don't feel it is important. It will likely give fewer cuts to the beginner's face, and if well honed, still mow down the whiskers with reasonable efficiency.
A thoughtful seller might select a razor over 17 degrees for a newbie looking to buy his first razor, though, if he normally notices things like bevel angle. Lots of guys just don't pay any attention to it and don't feel it is important. It will likely give fewer cuts to the beginner's face, and if well honed, still mow down the whiskers with reasonable efficiency.
For anyone who can't be bothered reading through my quite long post in the link above, it's basically all about friction*...
If you decrease the bevel angle you increase the Normal force exerted outwards perpendicular to your face, which increases friction between the razor and your skin. And if you increase friction beyond a certain point you'll cut yourself. You can also increase the Normal force by applying more pressure when shaving, you're more likely to cut yourself then too, obviously.
You could combat your higher bevel angle by lowering the angle you shave at, but that was @rbscebu 's original point - you need to be more careful shaving with a smaller angle bevel, because you need to do it at a lower angle.
You can also decrease friction by decreasing the coefficient of friction; honing, stropping &c. to give you a very refined edge. Which explains the slightly counter-intuitive fact that you're less likely to cut yourself with a sharp razor. Obviously that only holds up to a certain point - you can make a razor so blunt that you won't cut yourself by removing any bevel, but you wouldn't be cutting hair either.
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However, if you start plugging numbers into the equations of all this - a couple of degrees difference in bevel angle is an almost insignificant different at the end. And it's far outweighed by the other variables; how much pressure you apply and how well honed your razor is. It does theoretically make a difference if all other variables are equal, but in practice you'd probably need to be talking bevel angle differences of 10+ degs for it to really have much of a noticeable effect.
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That's a slightly simplified version of the most important physics around it. There are probably a near-infinite number of factors you could also throw in which would also affect friction in small ways; differences in people's skins, type of shaving soap, temperature, shaving style, skin stretching &c. &c. &c. And all of that compound the fact that a couple of degrees difference in your bevel is pretty insignificant in the grand scheme of things.
* Friction = Coefficient of Friction x Normal Force. F = u x N.
If you decrease the bevel angle you increase the Normal force exerted outwards perpendicular to your face, which increases friction between the razor and your skin. And if you increase friction beyond a certain point you'll cut yourself. You can also increase the Normal force by applying more pressure when shaving, you're more likely to cut yourself then too, obviously.
You could combat your higher bevel angle by lowering the angle you shave at, but that was @rbscebu 's original point - you need to be more careful shaving with a smaller angle bevel, because you need to do it at a lower angle.
You can also decrease friction by decreasing the coefficient of friction; honing, stropping &c. to give you a very refined edge. Which explains the slightly counter-intuitive fact that you're less likely to cut yourself with a sharp razor. Obviously that only holds up to a certain point - you can make a razor so blunt that you won't cut yourself by removing any bevel, but you wouldn't be cutting hair either.
---
However, if you start plugging numbers into the equations of all this - a couple of degrees difference in bevel angle is an almost insignificant different at the end. And it's far outweighed by the other variables; how much pressure you apply and how well honed your razor is. It does theoretically make a difference if all other variables are equal, but in practice you'd probably need to be talking bevel angle differences of 10+ degs for it to really have much of a noticeable effect.
---
That's a slightly simplified version of the most important physics around it. There are probably a near-infinite number of factors you could also throw in which would also affect friction in small ways; differences in people's skins, type of shaving soap, temperature, shaving style, skin stretching &c. &c. &c. And all of that compound the fact that a couple of degrees difference in your bevel is pretty insignificant in the grand scheme of things.
* Friction = Coefficient of Friction x Normal Force. F = u x N.
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I did the calculation from a photo that @Ice-Man posted and I was surprised at the result.
Koraat Opinions
Hello all: I'm new here, so I'm interested in your opinions. I realise that my question could be one of those "kill the messenger" things....but I would appreciate if you can bear in mind, I'm just asking a question. I recently ordered a Boker Feldmann, and was contacted by the owner of the...
From the photo it looks like the Koraat has a bevel angle around 20 degrees without considering honing with tape. I would have expected a lot less, but that confirms what @str8six posted on that thread about Koraat.
Hmmmm just to add here that your way out with 20degrees, in fact it is 17.2 and that is with kapton tape not 3m so without tape you would be near 16.5.
So that proves taking a photo with an app is way way out so stick to the good old method vernier calipers and get a true reading.
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I think factors like edge finish, grind, weight and size makes a bigger difference. I got a new razor recently, which is 6/8 with the longest blade i have handled to date. The scales of this razor is on the heavy side of what i am used to, which really offset the balance of the razor. It is a nice razor, but i was really surprised by how this affected the way this razor handled. This is a little off topic, and might be just a personnel preference. If i should give advise to my self starting out, i would get an 6/8, 1/4 to 1/2 hollow ground razor with compact blade. For some reason i find the heavier blades to do better going against the grain then the extra hollow ground razors, regardless of bevel angle and type of edge.
I have an extra hollow ground 7/8 böker razor that is a challenge to use against the grain. My 7/8 hart razor just glides through.
I think the thinner grind makes the razor flex and dig in more. I have not measured the bevel angle of this razor, but it might benefit from a more obtuse angle, or it just needs a smoother edge.
I have an extra hollow ground 7/8 böker razor that is a challenge to use against the grain. My 7/8 hart razor just glides through.
I think the thinner grind makes the razor flex and dig in more. I have not measured the bevel angle of this razor, but it might benefit from a more obtuse angle, or it just needs a smoother edge.
Spine thickness/Active width X 57.3 Degrees = __Degrees
