wider bevel=more flex?

Hey all,

So one of my razors, a 5/8" King Cutter, was obviously well loved by it's previous owner/honer, since it has a very flattened spine and now a pretty wide bevel as a result. It does shave well, so it's not out of the rotation yet!

But I have noticed that it doesn't cut as well around the curves as do other razors with a very narrow bevel. All my other razors are hollow also, about 5/8", and are german steel (with the exception of one). I couldn't help but wonder if it's because of the wider bevel. Does this create more flex in the metal at the edge? It would explain why it performs differently around curves, but not on flatter areas where there wouldn't be any lateral force on the edge. It does seem logical, since the wider the bevel, the wider the area of the blade that is sharpened VERY thin....:shrug:

Just a question I thought of and thought I would see if anyone knows the answer!

P.s. I would love to get a 1/4 hollow razor to try a heavier grind.....I think it would suit my beard type better. :D

i think a little differently and i am not sure i am correct or not.wider edge could make edge brake easier but sharpness of the blade should be same.Cutting edge is the same thickness .In wider edge as you mention thin part of the blade is more then regular blades edge and support as a result will be less .in this case if you shave heavy beards then it could brake down the edge easier then normal blade..Sharpness of the edge not changes, i agree it will be more flex too.Lets see what others think this is my 0.02 cent

I think the sharpness of the actual cutting edge depends on the steel used, the inclusive bevel angles, and how well they meet (i.e. level of polish/grind). The edge, sharpness wise, doesn't care how much mass is behind the bevels.

Flex-wise, the amount of steel behind the edge (full-hollow vs. wedge vs. "singing" grind) has a major effect on flex, but little effect on edge sharpness. The thinner grinds do sharpen up faster (sometimes) because there is less steel to remove.

Basically, I agree with hi_bud_gl. I just like to make it sound more complicated. :D

I'm not sure about the bevel flexing, but when it comes to the razor flexing, blades with wider bevels tend to flex less. (Wedges have wide bevels because they are thick and they don't flex; full hollows have narrow bevels because there isn't much metal in there, and they flex a lot.)

In your case, a full hollow, thinly ground razor with noticeable hone wear on the spine, the wider bevel would indicate the possibility of more flex. There is simply less steel behind the edge to keep the blade from flexing.

Try a wedge, get a Wapi from kenrup. It has very good swedish steel and a stiff single concave grind.


Just my $.02,:)

Couldn't flex be good? It would conform to the countours of your face more.

When I use a wedge I tend to use a bit more pressure., I think the contours of my face conform more to the razor where the full hollows conform more to my face (I get the same results with both but I think I prefer shaving more with a wedge).

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Originally Posted by holli4pirating

I'm not sure about the bevel flexing, but when it comes to the razor flexing, blades with wider bevels tend to flex less. (Wedges have wide bevels because they are thick and they don't flex; full hollows have narrow bevels because there isn't much metal in there, and they flex a lot.)

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Although wedges may have wider bevels, I think the rigidity (i.e. less flex) of the edge is a result of the thicker grind, not because of the wider bevel.

Hollow grinds do have more flex, but this isn't a result of the bevel width so much as the grind of the razor overall.

If a narrow bevel on a hollow ground razor still has more flex than a wedge razor with a wider bevel, then wouldn't a wider bevel on a hollow make this gap in flex even wider? (metaphorically speaking...)

BTW I have no proof for my ideas, I am merely hypothesizing. But I welcome more disagreement, it makes for interesting conversation. I don't mind being wrong! :p

Two parameters define the width of the bevel.

1. the bevel angle.
If the angle is smaller (due to a reduced spine) the bevel sides will become wider. The smaller the angle, the more flexible the edge, and it will also be a bit weaker.

2. the thickness of the blade.
A full hollow has a very thin blade, hence a small bevel is to be expected. A wedge has a thick blade, hence it will carry wider bevel sides. In this case the wider bevel will be a bit sturdier, because it contains more steel for the same height. (it has a wider base).

If you see wide bevel sides on a full hollow razor, that always means that the spine underwent a lot of honing wear. The steel of a spine can possibly be softer than the edge. As a result the bevel angle of some razors slowly diminishes over the years of honing. At a given point I believe that will start to have an influence on the durability of the edge. It depends on various other factors, such as beard type, when that starts posing a problem.

If the blade is thin enough to flex, so will the entire edge, for it is even thinner.
If the blade is thick enough not to flex, only a the last bit of the edge is free to flex, from the point where it becomes thin enough to do so.

In my opinion, flex helps the edge to follow the landscape of the skin surface better. At the same time those edges might have problems shaving a coarse, or poorly prepped beard. They have a harder time resisting serious cutting stresses.

Bart.

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Originally Posted by Bart

Two parameters define the width of the bevel.

1. the bevel angle.
If the angle is smaller (due to a reduced spine) the bevel sides will become wider. The smaller the angle, the more flexible the edge, and it will also be a bit weaker.

2. the thickness of the blade.
A full hollow has a very thin blade, hence a small bevel is to be expected. A wedge has a thick blade, hence it will carry wider bevel sides. In this case the wider bevel will be a bit sturdier, because it contains more steel for the same height. (it has a wider base).

If you see wide bevel sides on a full hollow razor, that always means that the spine underwent a lot of honing wear. The steel of a spine can possibly be softer than the edge. As a result the bevel angle of some razors slowly diminishes over the years of honing. At a given point I believe that will start to have an influence on the durability of the edge. It depends on various other factors, such as beard type, when that starts posing a problem.

If the blade is thin enough to flex, so will the entire edge, for it is even thinner.
If the blade is thick enough not to flex, only a the last bit of the edge is free to flex, from the point where it becomes thin enough to do so.

In my opinion, flex helps the edge to follow the landscape of the skin surface better. At the same time those edges might have problems shaving a coarse, or poorly prepped beard. They have a harder time resisting serious cutting stresses.

Bart.

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Nicely put Bart :D

Here is my rebuttle to the legend of the Wapi being a thick, beefy grind:

That pic was taken using very light pressure of the blade against the edge of my desk. It flexed back immediately from the distortion seen there.



I subsequently re-ground that Wapi, and you can see here, that as a result, the bevels got much wider, and I can tell you that there was no flex remaining as there was in the original blade.

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Originally Posted by Seraphim

I subsequently re-ground that Wapi, and you can see here, that as a result, the bevels got much wider, and I can tell you that there was no flex remaining as there was in the original blade.

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Interesting....that must be because the new bevel is now in the thicker part of the blade, since it's closer to the spine....:shrug:

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Originally Posted by Seraphim

That pic was taken using very light pressure of the blade against the edge of my desk. It flexed back immediately from the distortion seen there.



I subsequently re-ground that Wapi, and you can see here, that as a result, the bevels got much wider, and I can tell you that there was no flex remaining as there was in the original blade.

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I'm very puzzled, are you saying that the Wapienica flexes less after you have ground it thinner?

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Originally Posted by Bart

I'm very puzzled, are you saying that the Wapienica flexes less after you have ground it thinner?

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Yes, as the thin, unsuppported edge part was removed, and thus the bevel is now formed on the thicker portion of the grind:

Bart, I think he took some off of the blade as Dave said and got into a thicker part above the original edge. :shrug:

Dave, just for kicks I would take that blade and breadknife it down aways. Then I would use one piece of tape to make up for the spine wear. get a decent bevel on it and then add two more as Tim Zowada does and create a double bevel. Might be stronger and hold an edge better ? Interesting experiment anyway if you're into trying that sort of thing.

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Originally Posted by Seraphim

Yes, as the thin, unsuppported edge part was removed, and thus the bevel is now formed on the thicker portion of the grind:

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Ah, you ground it smaller, instead of thinner...
What a great relief. I almost thought someone had been tampering with the laws of physics...:D
Thanks for the clarification Seraphim (and Jimi)

Bart.

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Originally Posted by Bart

2. the thickness of the blade.
A full hollow has a very thin blade, hence a small bevel is to be expected. A wedge has a thick blade, hence it will carry wider bevel sides. In this case the wider bevel will be a bit sturdier, because it contains more steel for the same height. (it has a wider base).

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Not sure if you said that quite right? Assuming that "wider bevel" means that the bevel is "taller" extending further toward the spine from the edge then, at the same height (distance from the edge towards the spine) it would only contain more steel if the bevel angle is wider. The implication being that wedges have thicker spines for the same width blade.

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Originally Posted by Quick

Not sure if you said that quite right? Assuming that "wider bevel" means that the bevel is "taller" extending further toward the spine from the edge then, at the same height (distance from the edge towards the spine) it would only contain more steel if the bevel angle is wider. The implication being that wedges have thicker spines for the same width blade.

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Let's try a quick drawing.
On a theoretical full wedge, the bevel is equal to the razor. If we start to take away steel, by hollowing the sides of the wedge, we also take away steel from our bevel sides. They simply can't extend that far anymore because there is no steel to occupy. The hollower, the lesser steel left to be part of the cutting bevel.
One way to look at is is to realize that on a hollow razor, a part of the cutting bevel can't exist, because it was already ground away by the maker of the razor. In a way of thought, part of the steel has been removed for us during the production so we don't need to remove it during sharpening. (that is one of the historical reasons for hollowing a blade)

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Originally Posted by JimmyHAD

Dave, just for kicks I would take that blade and breadknife it down aways. Then I would use one piece of tape to make up for the spine wear. get a decent bevel on it and then add two more as Tim Zowada does and create a double bevel. Might be stronger and hold an edge better ? Interesting experiment anyway if you're into trying that sort of thing.

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That would actually make for a good experiment! I would have to get my nerve up first though...something about breadknifing an already shave-ready edge just doesn't sit right in the gut!

Wow! I wasn't aware of that. You mean that the blade is actually thinner at the full hollow point than at the edge?

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Originally Posted by Quick

Wow! I wasn't aware of that. You mean that the blade is actually thinner at the full hollow point than at the edge?

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No, the drawing was made too hastily to be accurate in that respect.

I am starting to be confused. Are you still disputing my simple observation that a wedge is beefier, also at the cutting bevel?

Imagine that we would hone a wedge, and next regrind it to a full hollow, without damaging the very edge. It can't be that hard to see how the lower part of the original bevel would be ground away too leaving less wide bevel panes.

No?

No.

Just for example.
Lets say you start at the very edge and start heading for the spine. Lets say that the bevel width (flat side of the bevel measured from the very edge towards the spine) is 1 mm. In your first example you use the term "height". I'm assumed this was the same measurement you were refering to?
Let's say that the bevel angle is 20*

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2. the thickness of the blade.
A full hollow has a very thin blade, hence a small bevel is to be expected. A wedge has a thick blade, hence it will carry wider bevel sides. In this case the wider bevel will be a bit sturdier, because it contains more steel for the same height. (it has a wider base).

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If you measure at the same bevel "height"
and you compare equal bevel angles. Then the bevel itself has to contain the same amount of steel.

I think I understand what you were saying but I think you may have mixed two thoughts.

1) In general, wedges will have wider bevels due to less hollow in the blade. Wider bevels will contain more steel simply due to triangle geometry. (but at the same time they would have more height to the side of the bevel).

Or

2) Were you saying that, generally, wedges have a wider spine and therefore more bevel angle. So measured at the same height up the side of the bevel they would contain more steel. (different bevel angles)


Haha, it would take about 10 seconds to resolve this if we had a white board. It would take me hours if not days to produce illustrations like yours.:bow

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Originally Posted by Quick

Haha, it would take about 10 seconds to resolve this if we had a white board.

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So true.:)

I have been thinking we kinda agree from the start, only use different words for different terms.

Let's rule out the spine thickness. In my first point (that states that bevel planes grow wider with diminishing bevel angle), the grind must be constant, but the spine must vary.
In my second point (the one we seemingly disagree upon) I start from a constant spine thickness.

So, with constant spine thickness, let's assume we are going to cut a strip of 5 mm of two razors, parallel to the very edge. Hence the strip will hold the edge and then some.
Now let's compare those strips:
The first strip comes from a wedge. The bevel sides will occupy a big part of our strip, if not all the strip.

The second strip comes from a full hollow. The bevel sides will occupy only a narrow part of out strip.

The bevel angle on both strips would be equal. But the bevel can't run as far down on the second strip, because their is no steal where it can run into. That steel was ground away by the person that made the razor.

Bart.

Yep. 100% with you there. It was the "height" thing that I don't think should have been there.

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In this case the wider bevel will be a bit sturdier, because it contains more steel for the same height. (it has a wider base).

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See, I read that as "height of the bevel". Now I'm thinking you meant height of the bevel for the wedge case and at that same height (which would extend above the bevel in the hollow case). I was pretty sure I understood what you were saying but like I said, I thought maybe you didn't type it quite right?

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Originally Posted by Quick

Wow! I wasn't aware of that. You mean that the blade is actually thinner at the full hollow point than at the edge?

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Yup if it's really hollow, you can see a "belly" down near the cutting edge where the balde gets fat again before narrowing down to the final cutting edge.

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Originally Posted by Quick

Yep. 100% with you there. It was the "height" thing that I don't think should have been there.



See, I read that as "height of the bevel". Now I'm thinking you meant height of the bevel for the wedge case and at that same height (which would extend above the bevel in the hollow case). I was pretty sure I understood what you were saying but like I said, I thought maybe you didn't type it quite right?

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Well yes, we speak a form of local Dutch back home in Belgium, but most Dutch members wouldn't understand half of it.:D
So excuse my poor English. I use many expensive words to make it sound intelligent, but the truth is that it is sometimes very hard to express my thought with any precision.:shrug:
I clearly meant an imaginary strip of steel of equal width on both razors, when I wrote "same height". It's not the first time someone needs to step in and clarify my thoughts...
Thanks for that,

Bart.