Bevel Angle | TomoNagura.Com | Keith V. Johnson

Bevel Angle | TomoNagura.Com | Keith V. Johnson

 Why the Bevel&#;s Angle is Important

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First off, I don&#;t subscribe to robotically checking the angle on every single razor. Not at all. Checking the angle is something I do when I am trouble shooting, or when I suspect that something in the blades&#; geometry is seriously whacked. Similarly, I only recommend that others do so when they have expressed issues with attaining maximum sharpness, or their razors are dulling too quickly, or they have posted an image that indicates geometry issues. Honing on tape is another situation where knowing what you&#;re dealing with first is a good idea.

The angle of the bevel, which creates the cutting edge, is super important. Period. I know that some people don&#;t agree, but I&#;ve found that all of the naysayers have never checked bevel angles and have never corrected geometry to achieve a desired angle. But factually, if someone has not measured bevel angles, and they also have never removed steel off a spine to bring the angle from 20˚ down to 15˚, they really aren&#;t in a position to authoritatively disqualify the importance of checking the bevel&#;s angle. 

Remember - knowledge is power. 

Simply put, the more we know about our razors the better off we are. 

Also remember this &#; ignorance is never spoken of in a positive light.     

The angle is important &#; if it wasn&#;t, razors would not have been designed the way they are; to be honed spine-on-stone so the angle can be maintained. If the angle did not matter, they would have just made a blade without consistent geometry and everyone would just freehand their sharpening efforts. I think the earlier wedge-ground razors suffered from this initially. However, it is obvious that manufacturers incorporated designs where the spine was also a sharpening guide.  

Safety razor blade manufacturers have, in the past, marketed with their blades based on their geometry &#; I recall a poster about Feather blades that showed the triple bevel with each separate bevel&#;s angle highlighted. Same for a type of Gillette blade too, but I forget which one. 

So, we see that the angle of the bevel is a major concern. 

But why? 

Well, because the edge/blade are a sum of the parts, and to achieve a desired result, for the tool to work properly, we have to consider the entire picture right down to the steel&#;s composition. 

The bigger picture must include the type of steel; it's hardness from tempering and it&#;s wear resistance which is dependent upon its chemical makeup and how it was forged. Steel isn&#;t just a simple mashup like cake batter, there is a grain, a crystalline structure, and these factors matter. Finally, when we have digested the bigger picture, we need to establish the parameters of what we are trying to achieve with this tool. The cutting edge needs to fall into a &#;zone&#; where cutting efficiency, face feel, and edge longevity are not only acceptable, we want to achieve the max possible performance in each area of concern without compromising the other qualities. In other words, we need to achieve an acceptable balance of performance in all areas of concern. In this arena, science, math and physics rule the day. 

We also need to recognize that personal preferences factor in too, but I&#;ll get to that later. 

Without getting into actual steel types, I&#;ll be as general about all of it as possible. What holds true for some Sheffields might not apply to the harder Swede steels. But, overall, the story is always the same, even though the actual numbers might change a bit here/there. 

Every blade that is ground to a cutting edge is going to have limitations that we must respect. To improve cutting efficacy, we can compromise on bevel angle by making it more acute, but we will &#; most likely &#; reduce edge longevity. We can increase longevity by making the angle more obtuse, but the edge will, most likely, not cut as well. Too steep might not feel good on the face but cut wickedly, too obtuse might feel good on the skin but tug on whiskers. 

As Barbra Eden once said - "You can't irrigate the desert without draining the ocean". 

If we are cutting heavy rope, we have to have a blade that is set up for that. If we are cutting whiskers, it&#;s a different story. So, the task at hand matters a lot. 

We don&#;t use hatchets for slicing bread. 

For more information, please visit What Degree Should A Bevel Be At When Welding Pipe?.

About sharpness &#; most people regard edge width to be the main critical concern where sharpness is concerned. To a lesser degree, the topography of the edge&#;s apex can be a factor also. It can be smoother or toothier, and that can aid or distract from its cutting ability. But at the end of the day, width of the edge is the common denominator that must be factored in first and most heavily. Edge width is controlled by bevel angle and only bevel angle. 

Whether it&#;s a Tamagahane Deba, a Blue Super Steel Kamisori, or an American Steel full hollow razor made for a now defunct drugstore &#; each blade has its limitations and the design of the tool for the intended purposes must fall within spec. 

In this discussion, I am mostly concerned with straight razors. And, one might say that most straight razors were most often designed with bevel angles between 16-19 degrees. Certainly, over time, this has been proven to be how the majority of straight razors are ground. Some might be a bit over, other a bit under. We&#;re looking at a majority here. Verhoeven noted that there were no hard and fast rules here. But he also noted, for razors, alpha angles of 11-12˚ and beta angles of 17-19˚. He also noted a lack of edge retention with more acute bevel angles. 

The edge geometry we see on our blades was chosen by the manufacturers after much R&D testing &#; they balanced the cutting performance against how the blades felt on the skin vs how many shaves they could expect a blade to deliver. It&#;s a 3-way see-saw with some latitude and wiggle room for the engineers to play with. 

So, if there is a range of degrees that a razor&#;s bevel can fall into without being an issue, why do we care? 

Because, over time, things change. A razor designed and ground originally in the s might not be within spec today. Across 150 or more years, honing atrocities may have occurred. I can&#;t remember exactly how many wedge blades I&#;ve handled that came in with angles over 20˚ but there were many of them and none of them shaved well at all. Putting tape on the spine only exacerbated the issue. Some softer do much better with bevels approaching the upper limits &#; these are the softer Sheffies and they shave, but perhaps not as laser-like as blades made from harder steels that take a more acute angle. 

Similarly, I have seen a ton of full hollows that have been the victim of spineicide by new honers using way too much pressure, the wrong stones, both, all of the above and maybe some other stuff mixed in there too. I remember a 15/16 Dorco that was honed by Godzilla, the spine seemed to be almost non-existent and the bevel&#;s angle averaged out at about 12˚. It would not take an edge worth spit until the spine had 3-4 layers of tape added to it. The problem was proven by checking the bevel angle and then building up the spine to meet a decent parameter. 

New razors out of China suffer from, among things, the opposite situation; the spines are too thick and they shave like dogs. If you prove the angle to be a certain degree, then you can figure out how much steel to take off the spine. The math is simple, the work is a little bit more difficult though, especially when you factor in needing to take equal amounts off each side. 

Does a razor shave better at 17˚ than it does at 16˚ or 18˚? Proving or disproving that to be true/false would be impossible, but it&#;s not the point of this discussion.  

We want to check the angle, so we can make educated decisions as we progress with our honing progression or troubleshooting. We want to be sure we are in the good zone and we want to eliminate variables. Where exactly the razor is, is less important that whether or not the edge is somewhere in the good zone. Sure, I have experienced the difference in feel and performance in razors after changing the angle by a single degree &#; I&#;ve done that many times. But &#; unless someone has a lot of free time and is uber-particular, dropping a blade from 17˚ to 16˚ is a lot of work for a marginal, if any, bump in performance. Yes, I&#;ve done it &#; and I&#;ll do it again but that&#;s me and how I go about doing things. I do not suggest that anyone undertake that sort of project without understanding it&#;s mostly an educational concern.

But dropping the angle from the stock 22˚ to 16˚ is definitely something to consider when you&#;re working with a Gold Dollar, or similar type of Chinese razor with a profile that&#;s better suited to a butter knife.  

I hone a lot, more than the average bear I think. So I run into some things that someone that doesn&#;t hone quite so often might not ever see. Basically, someone without much experience due to a short time honing, or maybe honing only in their comfort zone for a long time, might not realize that the situations that I'm describing exist. I can understand that, in fact, it&#;s what I attribute most of the &#;bevel angles don&#;t matter&#; contrarian chatter to. But just because someone doesn&#;t do something, that doesn&#;t obviate that particular something from reality. Their ignorance might remove logic, reason and fact from their little world but there is always a bigger picture to consider. 

I suppose that another consideration is that everyone has different skin, different whiskers and different shaving needs. So, an edge that is unacceptable to a daily 3-4 pass shaver with titanium wire whiskers might be a plausible concern for a once weekly shaver else who&#;s beard has the consistency of damp moss. Basically, we recognize that there are different needs on the table, and some of those needs are not as critical or demanding as the others. 

However, those lesser needs/demands are a smaller picture and they do not remove or negate the importance of the science, math and physics behind the razor&#;s geometry.  

Do some razors fall outside of spec and still work fine? Sure &#; nothing in this game is a 100% given that is written in stone. We have to test each blade and take each one on its own merits. But knowing how to check, and actually checking though, this raises one&#;s level of knowledge. 

As noted earlier &#; knowledge is power and ignorance is pointless. 

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