Angle of Attack

Ok, now what's he yakking about, right??

Think of a guillotine. In fact do a Google search if you are not familiar with one. Basically it is a device with an angled blade that drops straight down and slices through, ummmm, stuff.

Imagine if the blade was, instead of angled, placed straight across so that when it dropped on, stuff, it impacted with it's full length all at once. Instead of slicing through stuff, it would tend to crush, stuff.

That blade angle is the key to quickly and cleanly slicing, stuff. Note that the blade travels in a single plane of motion, straight down. There is no lateral movement, no forward nor backward side to side plane of movement. The angle of the blade does all the work.

This is exactly how a straight razor works to cleanly slice through stuff, like beard hairs. If the blade meets the hair head on, it will effectively try to crush through instead of slice through. Read: pulling and irritation.

The trick, as you move the razor around the different angles of your face, is to maintain that crucial angle of the blade where it meets/attacks your beard.

The other trick is to hold that single plane of movement so that the blade never, and I repeat NEVER, travels in a tangential or parallel plane to the skin.

Good luck,

Scott

The only problem with your theory is that if it was true you couldn't do the Hanging hair test. The hair meeting the edge of the razor straight on would then crush the hair and not cut it unless you presented it at an angle.

Just thought I'd throw a fly in your ointment!

Scott,

Do I understand this concept to mean that instead of a straight n-s pass, we should move the blade in a kind of n-sw or mild sweeping motion?

Think snowplow blade.

Ok, let me restate this part. The broad plane of the blade does in fact move tangiential to the plane of the skin, but...

Consider the point of the razor a reference point.

The point never moves forward nor behind the plane of motion as the razor travels over the face.

Hopefully that is more clear.

Scott

PS - bigspender, I'll address your pesky 'lil fly later. I'm at work stealing just a moment to clarify the above, but I gotta go!

Scott,

I think I agree with what you're saying about the angle, but I'm not sure about one part of it.

First off, using the blade with an angle makes a huge difference. For me, either angling the toe of the blade downward for the N-S strokes, or else using a slight toe-leading motion on the stroke makes it cut through the tough beard on my chin a lot easier.

I'm not sure about the "crushing" you talk about, though. If you watch the National Geographic shaving video, they talk about a razor being so sharp that it just slides between the hair molecules. So regardless of whether or not it slices at an angle, you're breaking molecular bonds, not tearing them apart like a less fine edge would do.

I think analogies to a knife blade or guillotine break down for that reason. I think a knife rips molecules apart. A razor almost nudges them aside.

What does this mean? I'm not sure. I agree with your observation, but I have some questions about why it's true. Maybe the angle helps a less sharp razor keep cutting.

Anyway, not trying to pick a fight. I'm enjoying your "lessons" lately.

Respectfully,
Josh

That's why 'smiling' blades shave so great...you're always presenting a curved edge to the area being cut, which effectively presents a side-to-side sawing cut without actually moving the blade side to side (on a microscopic scale, of course).

Quote:

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Originally Posted by joshearl

I'm not sure about the "crushing" you talk about, though. If you watch the National Geographic shaving video, they talk about a razor being so sharp that it just slides between the hair molecules. So regardless of whether or not it slices at an angle, you're breaking molecular bonds, not tearing them apart like a less fine edge would do.

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Edit: the following is wrong - human hair is made of keratin, not collagen. Perils of posting under the influence. The truth, however, is even worse for the "sliding between molecules" theory. See the followup post.

Human hair is made of collagen. The basic collagen molecule is 300nm long and 1.5nm thick - basically a microscopic rope. Since a micron is 1000nm, this means the molecules are roughly 1/3 micron long.

Compare that to the grits we use for shaving. We can pop hair with a 6 micron hone. Obviously the fin is thinner than the grit size, but it seems unlikely that an edge that coarse is somehow missing the main body of these "ropes" and instead slides between the ends of adjacent "ropes" that are twisted together to make up a hair. It seems more likely that it really does tear these "ropes" as it cuts, or possibly just catches the molecules in front of the fin and pulls the hair in two, or some combination of the two.

mparker,

The video also shows the hair bending slightly before it starts to cut. Could the razor blade be sliding along the body of the collagen molecule until it finds the end, then sliding in?

It seems unlikely to me that the blade could then thread its way between molecules with the measurements you're giving. Maybe National Geographic was oversimplifying?

Just trying to fit the pieces together...
Josh

NG was oversimplifying. Three collagen molecules (which are already pretty large compared to the fin of the blade) are twisted into longer fibrils. These molecules are staggered within the fibril, and as one collagen molecule ends another takes it's place (so a fibril may contain thousands of collagen molecules, but only three at any given place). If a collagen molecule is a short cord, a fibril is a very long rope. These fibrils are arranged differently for hair, cartilage, corneal lenses, and all the other stuff that collagen is used to build in the body. But for hair they're bundled together and twisted like a giant cable.

(I can't believe I'm about to use that wikipedia as a reference)

http://en.wikipedia.org/wiki/Collagen

Do you ever get the feeling that we overanalyze this stuff? :)

Thanks for all the great info. I love SRP.

Josh

by "overanalyze" - what exactly do you mean? Can you give us some techniques you've found successful in overanalyzing? :roflmao

Oops, hair is keratin not collagen. The two are similar though not identical. Keratin is even longer, contains sulphur, and are even more tangled

"The basic unit of hair is a long strand of protein chain which forms into an alpha helical secondary structure. Three of these alpha-helical lengths of protein wind around each other to form a structure called a protofibril. In turn, a microfibril is assembled from eleven protofibrils arranged in a way that involves nine protofibrils wound around two protofibrils. Hundreds of microfibrils are then packed together with a sort of protein glue to form a macrofibril. These macrofibrils are, in turn, packed within the body of a dead hair cell. A typical hair fiber is about ten hair cells in diameter."

http://dl.clackamas.cc.or.us/ch106-08/structur1.htm

In short, it seems even less likely that a razor blade will somehow thread it's way through the twisted tangle, finding the gaps between the molecules and sliding them apart.

Alright, you guys are sick. I tried to keep it simple with my guillotine and slicing analogy. But yoose guys. Geeze!

Anyways, I'm just glad to stir it up a little and get those brain cells working. :D

Just don't kill it too much for the newbies sake.

Scott

I'll also make it simple: I would not want a blade to be slicing anything on my face. If you attempt a slicing motion, you better be a big fan of scars and self-mutilation. Scything motion is a different story and can come in useful with a dull blade, but if your blade is truly shave-ready it's almost redundant.

Aren't you confusing the angle of attack (ie spine lift) with the angle of the blade cutting edge?

In a guillotine, the blade's edge-spine plane is actually perpendicular to the neck. In a shaving equivalent it would be like having the blade absolutely parallel to the face, which would leave stubble as long as the razor's spine is thick, assuming it would cut all of the hair in a reasonable number of passes.

I forgot to mention that the blade would be angled to the path of the pass.

Quote:

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Originally Posted by honedright

There is no lateral movement, no forward nor backward side to side plane of movement. The angle of the blade does all the work.

Scott

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Wrong.
By inserting an angle, you create lateral movement. If you look at it from the razor's point of view: For every mm down, you go 0.x mm sideways.
Ergo there is lateral movement. You don't perceive it because it is hidden by the fact that you move in a straight line, but the edge itself goes partially sideways.

The Barbers Manuals posted in the help files talks about shaving with the toe leading.

http://http://straightrazorpalace.com/component/option,com_docman/task,cat_view/gid,19/Itemid,3/

Is that what you are refering to as "angle of attack"?

Dave

the science of shaving, eh? :D

Quote:

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Originally Posted by Bruno

Wrong.
By inserting an angle, you create lateral movement. If you look at it from the razor's point of view: For every mm down, you go 0.x mm sideways.
Ergo there is lateral movement. You don't perceive it because it is hidden by the fact that you move in a straight line, but the edge itself goes partially sideways.

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This is what i was trying to get at.

Quote:

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Originally Posted by Bruno

Wrong.
By inserting an angle, you create lateral movement. If you look at it from the razor's point of view: For every mm down, you go 0.x mm sideways.
Ergo there is lateral movement. You don't perceive it because it is hidden by the fact that you move in a straight line, but the edge itself goes partially sideways.

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The blade of a guillotine is supported, or firmly fixed, between two upright posts that allow the blade to travel in a downward direction only. The blade itself cannot move in any other direction. It is totally impossible without disrupting the integrity of the device. In other words breaking it. And then it wouldn't be a guillotine anymore and it wouldn't work.

The angled edge doesn't move either. As the blade travels down, it remains fixed (usually in a heavy wooden frame) in it's downward plane. It has to because of the way a guillotine is built.

The object being sliced also remains in a fixed position in space. Nothing, neither angled blade nor object being sliced, moves laterally. The angled presentation of the blade allows the cutting edge to meet the object being cut gradually, rather than all at once. This is what causes "slicing". It is an optical illusion that there might be any sideways movement of the blade. But the blade remains fixed in it's downward plane of movement.

In straight razor shaving, you are literally guillotining you beard hairs. Lateral movement of the straight razor equals cutting the skin.

Scott

Quote:

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Originally Posted by FiReSTaRT

I'll also make it simple: I would not want a blade to be slicing anything on my face. If you attempt a slicing motion, you better be a big fan of scars and self-mutilation. Scything motion is a different story and can come in useful with a dull blade, but if your blade is truly shave-ready it's almost redundant.

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Ok, don't get confused here. You are not attempting a slicing motion. The angle of the blade as it meets the hair is what causes the slicing. The only motion you are doing is downward (this is kind of misleading because the direction of movement may not always be "downward". Hopefully the readers here are getting the idea though). The angled presentation of the blade actually does all the work.

I'm not sure if "scything" is the same thing I'm talking about, but it may be.

Once again I have proposed a conception of a technique and apparently it is very easy for some to get the wrong idea.

Believe me, I would never suggest you do anything that would deliberately cause injury. I appologize if my descriptions are hard to follow though.

Let's leave it at this: if you are interpreting anything I've suggested as dangerous, or prone to injury, assume that you have mis-interpreted or mis-understood my instructions and re-read what I wrote. Better yet, ask me to re-explain.

Re-spectfully,

Scott

Quote:

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Originally Posted by FiReSTaRT

In a guillotine, the blade's edge-spine plane is actually perpendicular to the neck. In a shaving equivalent it would be like having the blade absolutely parallel to the face, which would leave stubble as long as the razor's spine is thick, assuming it would cut all of the hair in a reasonable number of passes.

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True, but a guillotine blade is shaped differently than a straight razor.

A guillotine blade is triangular, so even though the spine is perpendicular, the blade has an angled presentation.

Since the cutting edge of a straight razor is parallel to the spine, the shaver has to tillt the razor to get the same effect.

Scott

I think honedright is talking about drawing the razor against the face oriented like the second razor as opposed to the first.

If you draw the second razor at this angle, then the blade does indeed meet the hair like a guillotine meets the neck.

The angle of the flat of the blade off of the skin compensates for the bevel, thus presenting the edge to the hair more "head-on", wait, "head-off"? no, that's the guillotine! :roflmao

Quote:

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Originally Posted by spacetoast

I think honedright is talking about drawing the razor against the face oriented like the second razor as opposed to the first.

If you draw the second razor at this angle, then the blade does indeed meet the hair like a guillotine meets the neck.

The angle of the flat of the blade off of the skin compensates for the bevel, thus presenting the edge to the hair more "head-on", wait, "head-off"? no, that's the guillotine! :roflmao

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Oh so close! Just re-orient that second razor with the point lower than the heel and then you're right on. Thank you for the illustrations. A picture is worth a thousand words.

Now the trick, as I mentioned earlier, is to maintain that relative angle throughout the shave. Just takes some practice.

Scott

Quote:

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Originally Posted by honedright

Oh so close! Just re-orient that second razor with the point lower than the heel and then you're right on. Thank you for the illustrations. A picture is worth a thousand words.

Scott

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It seems to me that if you put some hard points in your strop that would scratch the steel and then stropped using an X pattern you would end up with scratches in line with the direction of movement of the razor assuming the razor is held like in the second picture (but with the point down). To me that indicates that stropping in a X pattern or with the heel leading is done in part to optimize shaving with the point lower than the heel.

Quote:

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Originally Posted by b0000urns

It seems to me that if you put some hard points in your strop that would scratch the steel and then stropped using an X pattern you would end up with scratches in line with the direction of movement of the razor assuming the razor is held like in the second picture (but with the point down). To me that indicates that stropping in a X pattern or with the heel leading is down in part to optimize shaving with the point lower than the heel.

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Hmmmmm....could be??? Actually, as I picture it in my mind, I think the point is leading when I strop. Yep, I just got up off of my butt and checked, and that is what I'm doing. Point leading.

Scott

Well maybe I'm confused. I visualize it as if one strops using an X pattern, starting with the toe off the leather and ending with the heel off the leather, then the alignment would be the same as stropping in a straight line with the heel leading.
Ryan

One of my barber text books has a good photo of what I do. In fact that is where I learned to do it. I'll try and copy it then post it to this thread.

If I am seeing what you are doing in your stropping video correctly it looks like you do a slant, toe to heel up heel to toe down, but i could be wrong there.

Don't take the few who seem to criticize too seriously they only post because they missed the point the first time. I've been able to follow what you have been saying pretty well, though it is a little more advanced thought and technique than I currently have at my disposal. Good post!!

Quote:

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Originally Posted by Wildtim

If I am seeing what you are doing in your stropping video correctly it looks like you do a slant, toe to heel up heel to toe down, but i could be wrong there.

Don't take the few who seem to criticize too seriously they only post because they missed the point the first time. I've been able to follow what you have been saying pretty well, though it is a little more advanced thought and technique than I currently have at my disposal. Good post!!

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Actually what I do is sort of arc the razor across the strop. And sometimes I draw the razor from the middle of the strop diagonally to either end. It all seems to work. Practice and experience are still key though.

And, in reference to the highlighted quote above:

I just don't want anyone to do something silly.

The only reason I post here is because I hope I have something of value to offer. I believe that if I can even help one person to improve, only just a little bit, then I've done something good. And that makes it all worthwhile.

That may sound sappy, but that's the way it is.

It's all fun.

Scott

I just didn't want you to think you were misunderstood by everyone. I usually don't post in the informative sections unless I need clarification on a point, and you guillotine analogy made sense to me right away. Of course I also understand a scything movement too, of course I have used a scythe but not yet a guillotine.:roflol:

Quote:

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Originally Posted by honedright

The blade of a guillotine is supported, or firmly fixed, between two upright posts that allow the blade to travel in a downward direction only. The blade itself cannot move in any other direction. It is totally impossible without disrupting the integrity of the device. In other words breaking it. And then it wouldn't be a guillotine anymore and it wouldn't work.

The angled edge doesn't move either. As the blade travels down, it remains fixed (usually in a heavy wooden frame) in it's downward plane. It has to because of the way a guillotine is built.

The object being sliced also remains in a fixed position in space. Nothing, neither angled blade nor object being sliced, moves laterally. The angled presentation of the blade allows the cutting edge to meet the object being cut gradually, rather than all at once. This is what causes "slicing". It is an optical illusion that there might be any sideways movement of the blade. But the blade remains fixed in it's downward plane of movement.

In straight razor shaving, you are literally guillotining you beard hairs. Lateral movement of the straight razor equals cutting the skin.

Scott

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No it does not.

Look. the blade is at an angle.
You are moving it straight down.
Ergo, the blad itself is at an angle with the movement.

Now, if you decompose the vector of that movement into 1 vector parallel with the blade, and one vector at a right angle with a blade, you'll see that the movement is made up of 2 non-zero vectors.

This means that there is lateral action at the same time as radial action.
if there was no lateral action at all, the blad would move 100% in the direction which is at a right angle with the blade, but that is not what's happening.

there are 2 movements at the same time, and the lateral movement is small, or yo u would indeed cut yourself, but it is there.

:w :gth

I'll go ahead and side with the guy that straight-shaves for almost as long as I walk this earth. :D

When starting I experimented with both ways and I noticed immediately it was a lot better/smoother when doing what honedright said. I still remember because I was wondering why with a M3 it goes better just straight down as opposed to an angle. :) (I still don't know why if anyone can fill me in?)