What are the differences in shaving attributes of different blade grinds?

[Doc Dan]

What are the differences in shaving attributes of different blade grinds? How is an extra hollow different than a hollow, or a wedge in effects, feel, shave-ability, and other things, for example.

I have only high hollow grinds, but one does have a belly/horizontal stabilizer. That one feels very different than the other two and sometimes I think it shave a little better, then other times I think one of the others does.

 

[JPO]

What are the differences in shaving attributes of different blade grinds? How is an extra hollow different than a hollow, or a wedge in effects, feel, shave-ability, and other things, for example.

I have only high hollow grinds, but one does have a belly/horizontal stabilizer. That one feels very different than the other two and sometimes I think it shave a little better, then other times I think one of the others does.

I like all types of grinds. However, i do think there is allot more things you can play with to change the shaving characteristics if you use different types of deeper hollow grinds. I doubt that i would be able to tell much difference between a 1/2 hollow compared to a 1/4 hollow, accept maybe the weight difference.

Here is just some comparisons to describe what i mean;

This is a Fillarmonica 14, full hollow.This is flexible but still has enough stiffness to it to be able to push through against the grain. The large blade size also matters allot. I would think that a 5/8 with the same grind would loose some of it's inertia, which is important. So blade size also matters, not just the grind.

This is a different full hollow grind. The blade dimension is quite similar. This razor does not have a stabilizer, so that also factors in. This blade feels quite different from the previous one. The thin part of the hollow grind extends a little further up from the edge, which makes it more flexible. This is nice blade, but the edge flexes a bit more going ATG. The Fillarmonica grind feels like a better compromise between flexibility and strength behind the edge.

I am struggling a little with this is type of hollow grind. The blade is light and stiff. In this case you don't get the weight advantage you have with a heavier grind, and the hollow part does not give you the flexibility you would expect from a hollow ground razor. So to me it is like a oddball. If you have a really tough beard, and you don't like a heavy razor i can understand why the added stiffness would help.
TI razor fall in the same categories for me. Light and stiff blades. Full hollow, but not thin enough to take advantage of the grind.

I do think the extra hollow ground blades require a shallower shaving angle, and a different technique then heavier blades.
I started with large 1/4 hollow blades, and did not like the full hollow, and extra hollow blades. Now i prefer thinner grinds. I find them allot more unforgiving if i use an open shaving angle then a heavier blade.
Larger 7/8 to 8/8 full/extra hollows also shave quite different then smaller blades with the same grind. They are usually better suited at going through heavy stubble ATG then the smaller blades. I am not sure why. Maybe it is the added momentum you get from the extra weight.

For me the best compromise is a full belly hollow, with a really thin hollow part and some meat on the belly to support the edge. Small changes is the grind changes the shaving characteristics allot.

 

[Doc Dan]

@JPO I certainly like my bellied hollow grind a lot. It is a spectacularly beautiful razor, but it shaves soft and efficiently.

I understand you to say that thinner grinds are more unforgiving than even a slightly thicker one. Also, that despite the grind, larger blades cut better than smaller blades. Did I get that right?

I'll throw in another thing. I have an H.Diamond 1000, a Japanese straight razor. Now, this blade is a deep full hollow and is approximately 5/8 or so. However, the blade is longer than a standard straight razor and that seems to stiffen the blade a bit, or something. This razor will go through many days growth effortlessly and without much vibration and I assume flex.

 

[JPO]

Also, that despite the grind, larger blades cut better than smaller blades. Did I get that right?

I just think they are different, and require a different shaving technique.

I like the larger blades, but my last three razors have all been extra hollow 5/8. They are like race cars. Nimble and fun to use.

I only have one old 7/8 TI razor with a thin grind and a belly. Even if the blade has some geometry issues it shaves better then the stiffer full hollow TI blades I have.
But that is just how I like them.

I don't like to generalise too much.

 

[Doc Dan]

There has to be a reason for the different grinds.

 

[Gamma]

Attributes assigned to grinds is probably more of a preferential thing than anything else.
Not everyone likes this or that grind, for their reasons, and the reasons vary from person to person.
For me its not so much just grind; size, grind, and blade/point style.
So a 1/2 Hollow 8/8 shoulder-less blade with a barber's notch is something I'd like probably.
A 5/8 with the same form factor - not so much.

As for grinds developing over the years, I think the craft developed at time went on and more refined profiles emerged. I recall reading a barber's manual where the author referred to wedges as 'old style'.... and how some still preferred them over hollow grinds. Everyone iikes what they like.

I am sure someone ground a hollow razor and said it was better because of x, y, & z. I am also sure that someone said, "nah, I like the wedge better".

I have read a ton of rhetoric about grinds, etc, over the years. For me it just boils down to having choices. 5/8 to 8/8, full wedge through full hollow. Everyone can find something they can get along with.

A 17 degree bevel is a 17 degree bevel, regardless of the grind or width of the blade behind it.
Hollowing the blade will lighten it, make it more flexible, but cutting efficacy is the result of edge development, not grind, width, type of point, presence of stabilizers, etc.

I prefer heft over flighty. I prefer stiffer over flexy. I prefer wider over narrow.
Not because those assets are objectively superior somehow though. It's just because that is just how I like a razor to be.

 

[Doc Dan]

I would assume that you are correct in wedge grinds being "old style." They are probably the easiest and most logical to grind first. Later, other grinds came along in order to thin the edge and extend razor life. A hollow grind, being thinner, is easier to sharpen on a knife and cuts really well. it can make thin, close cuts. However, it is easier to damage from impacts or simply by cutting something. I assume the same is true for a straight razor since it is basically a knife.

I look at a wedge as as sort of full flat ground knife blade. The full flat grind is great for many cutting tasks as an all around grind on a knife. However, as one sharpens, the blade gets thicker and is less efficient. It doesn't cut quite as well as a hollow grind as a rule. However, on a knife, when the medium gets closer to the spine, the FFG will cut better because there is no sudden thickening of the blade spine. However, if one is skinning something, or if one is slicing something thinner than the blade is tall, the hollow grind cuts better because it has less resistance.

That's all I know or surmise. I want to find out more and how it all applies to straight razors.

 

[KW Driver]

it largely comes down to face feel and enough mass to smoothly push through a beard in my opinion. it's a preference choice.

I very much agree with Gamma, but generally prefer a thinner razor. my sweet spot is a 6-7/8 hollow variation (full, bellied, extra). and I've shaved with 4/8 1/4s and hollows up to 8/8 wedges and hollows. unless I've got a 3+ day growth in which case I pull out a 1/4 hollow. it gets through the first pass with less tugging that I can feel. I don't prefer to shave every 1-2 days with a 1/4, and my wedge experience is with 7-8/8 wedges of yesteryear. they're too heavy and unwieldy to my taste. and the first use I had with one I toppped out a small mole that hollows conform around. didn't even know I had until I saw the blood. the blade never slowed down (did the same with a '11 R41 when I tried it out) . so they probably do work better on a thick, heavy, Mediterranean beard than mine. which is perfectly fine. I find a 1/4 does everything I need it to without the extra heft of a wedge. and I find 1/2 hollows to be basically the worst compromise of both grinds unless it has a supremely keen edge.

the key is to find your happy range and focus there.

 

[Gamma]

It wasn't me calling wedges 'old style' - that was read in a very old barber's manual. The author was discussing grinds and brought up two points of view about grinds. I don't recall the author stipulating over full or near wedge. I would assume he was referring to near wedges, not true wedges.

The point was, even back then, there were personal preferences in play, some liked heavy grinds, some preferred more hollow grinds.

It would seem that the evolution of putting a hollow in a razors grind had a lot to do with maintaining geometry during sharpening. Old full wedges often show no wear on sides of the blade. Spine wear becomes a 'thing' when we see a slight hollow in the grind.
Full wedges exist, but mostly we see near wedges with some hollow, and they often get classed as a wedge.

I don't see full hollows being easier to hone than a near wedge.
A 17 degree bevel is a 17 degree bevel, regardless of the grind.
So if a full hollow and a near wedge both have the same geometry, and edge condition, then the same work has to get done.
I don't think full hollows last longer.
I suppose one could argue that honing a near wedge is easier than honing a full wedge.
A full wedge would need to be re-tooled at some point.
One might argue that a hollowed razor needs to be reground also, to keep the degree of hollow intact. Otherwise a 6/8 full hollow might less hollow when 1/8" of blade has been honed away.

A hollowed grind in a knife is geometrically similar, but it's a different tool. So a thinner blade from a thinner grind will allow a different action - like filleting fish vs chopping through woody veggies. A razor though, it only goes through a whisker so 1" of thin blade doesn't allow a better cut. The bevel is wider than the whisker. Not really apples and apples here.

I have ever come across, on this topic, is "I think..."
Most of what is 'known' is conjecture and there are always opposing points of view.
I think it was Dovo that wrote about more hollowed grinds being more elegant with a better visual aesthetic. I can see that playing in heavily to be honest. Like gold wash, or other appointments that create a finer visual aesthetic.

Look at the barber's notch topic though, there is no 'proven to be correct' explanation for it's existence.

One guess is that barbers liked hollowed grind razors because they were easier to deal with.
They were lighter and more nimble.
To a barber that means less effort and greater speed and that adds up to more $$ and less stress.
I think the fact that all these grinds have existed sine they were available speaks to personal preference being the calling card. Thiers might want to tell me their extra hollow singer will shave me better but I know it doesn't shave me better.

 

[ZeelandsRoem]

Later, other grinds came along in order to […] extend razor life

I don’t see why hollow grinds extend the razor’ life. I doubt we will see many extra and full hollow razors past the 100 years old age. When they start rusting in the hollow area and the damage goes deeper into the steel, that razor is technically compromised (although some will argue it could still be used depending on some factors). With a wedge or near wedge, a regrind/sanding could clean the affected steel and turn it into a perfectly good razor, good for another 100 years if the regrind/cleaning was done correctly. With hollow, this is either not possible or it is very difficult.

I enjoy all the grinds and sizes though.

For everything else, I do agree with what Keith is saying.

 

[Doc Dan]

I don’t see why hollow grinds extend the razor’ life. I doubt we will see many extra and full hollow razors past the 100 years old age. When they start rusting in the hollow area and the damage goes deeper into the steel, that razor is technically compromised (although some will argue it could still be used depending on some factors). With a wedge or near wedge, a regrind/sanding could clean the affected steel and turn it into a perfectly good razor, good for another 100 years if the regrind/cleaning was done correctly. With hollow, this is either not possible or it is very difficult.

I enjoy all the grinds and sizes though.

For everything else, I do agree with what Keith is saying.

You might be right. I know that with a knife and a full flat grind (what is called a full wedge on a straight razor, basically) the more one sharpens the more metal is removed and the more the edge moves up to thicker and thicker metal. The knife will still be useable, but will not cut as well. I assumed the same is true for a straight razor.

 

[Frank Shaves]

I would just try different sizes and different grinds to see what you think. I did and I have a preference for around 7/8, near wedge/quarter hollow razors. They just feel good to me.

 

[Doc Dan]

Yes, but there must be some scientific reason for the different grinds. Perhaps some grinds are better for gorilla hair than others.

 

[Frank Shaves]

Grinding technology has evolved over time. Apparently, the technology to grind full hollow razors did not exist in 1850. The good news is that Andrejs at RigaRazor only makes razors with thick grinds. I guess even straight razors are subject to the circle of life.

 

[Goofy_Bee]

I read something about SR grinding. There are still some old literature and old grinders left, (if you can read german books)
The reason for hollow grinding (at all) is simple: honing.
To make a shave-ready sharpness you need a fixed honing angle. The design (spine thickness and blade width) is made to have the SR flat on the hone. But if the blade is flat ground you have to hone the entire blade face (plenty material to remove). If it's hollowed only the tip/edge and spine are in contact with the hone and you have to remove less material.
The differences between 1/4 - 1/2 - 1/1 evolved over time.
A 1/4 or near wedge is much easier to grind. You need only one grinding wheel/stone (the diameter depends on your blade width)
For a real full hollow you need more wheels/stones with different diameters (and a lot more skill). To make a wedge blade, more steel is needed. The full hollow blade blanks are "pre-hollowed" and therefore lighter (less steel is needed for production)
What's best for your face you have to find out by yourself. Hair and skin typs vary.
Some said that a wedge (due to its higher stiffness) are more unforgiving to your skin but more suitable for coarse whiskers. Full hollow on the other hand are more flexible and softer for your skin.
When it comes to full hollow only 2 points a relevant. The thickness of the soul ("Seele" in German - the thinnest point in the hollow grind) and the thickness of the Wate (don't know the english expression - the "Wate" is the area between belly and edge).
BTW a belly is always there (full hollow). In most cases it's is removed by buffing (pliesten) and that has no impact on the stability. But once the belly is completely removed and the hollow grind get thinner and thinner towards the edge the stability is gone. Then you have massive problems with honeing and ATG shaving.
Italian and spanish barbers requiered thinner blades than german barbers. When honing you remove steel and with time the edge moves towards the belly. If the blade is very thin ground they could hone them longer by themselfs before sent the SR to be re(hollow)ground. German barbers prefered more durability.
For comparison two different #14 (black - old Böker for italian market and red - MoDoSo Dorko for german market) (sorry for the bad quality pics) bothe are bellied full hollow #14 and really good shavers

If you are more interested in ginding, Ulrik (Koraat) explained a lot of his work in a german forum. (I hope it's allowed to link the post )
To much to translate, but google translator should be helpfull

Die verschiedenen Rasiermesserschliffe

Hallo, ich habe mir den Spaß gemacht und habe alle Schliffe die wir derzeit anfertigen können nebeneinander als Vergleich aufgereiht. Das entspricht natürlich nur unserer Art die Schliffe herzustellen. Bei anderen Herstellern fallen die Bezeichnungen vielleicht anders aus. Vielleicht hilft es...

forum-der-rasur.de

 

[JPO]

@Goofy_Bee great post, and some interesting points made.​

 

[JPO]

I am not sure where Ulrik got this from, and i could not find a good translation for the last orange line.
However, if this graph is reliable, you can understand why the 16-17 deg bevel angle is so common on allot of razors.
I have custom new razor that came with a bevel angle of around 14 deg. I needed to bump up the bevel angle to 16-17 before i felt the bevel angle was right when i shaved. This was on two almost identical razors with a slightly different grind. For me the bevel angle made a big difference, in addition to the grind difference.
So, bevel angle, in combination with grind also plays a role in how the blade feels and shaves.

 

[Goofy_Bee]

So, bevel angle, in combination with grind also plays a role in how the blade feels and shaves.

Indeed.

The orange line is "quality in HHT"

There is a cut off (or threshold) for the bevel angle due to meterial (steel) properties (grain structure). And for steel that's the 14°
I have a SR with a very thight angle too. This one I double tape before honing to increase bevel angle. The angle should be checked if problems occure with durability (edge retention) or sharpness at all.

 

[Frank Shaves]

Thanks for sharing, @Goofy_Bee!

 

[Seelector]

I had an interesting shave last night that confirms Ulrik’s chart.

I have a no-name Sheffield frameback (picture in the What Straight Did You Use Today thread) with a very high 22° (taped) bevel angle. The shave was tuggy (ie high cutting resistance) yet close with no skin irritation. It was comfortable after the shave but not so much during the shave.

I’m going to reset the bevel without tape which will bring the angle down to about 20° and see how it feels.