ShavingUniverse.com

Register a free account now!

If you are registered, you get access to the members only section, can participate in the buy & sell second hand forum and last but not least you can reserve your preferred username before someone else takes it.

Blade Geometry from custom razor maker Robert Williams

Gunner777

Well-Known Member
The email then his website post. Posted with his permission: Hopefully this will clarify the point I was trying to make yesterday. This for the benefit of those who are starting honing and could use solid info from a real pro.
http://customstraightrazors.com/wordpress/razor-edge-geometry-introduction/

With straight razors,
you need a bevel of 15-18 degrees for best results. Any less than
that is too fragile and anything more obtuse than that will likely not
be satisfactorily sharp. You are, however, free to use any of my work
you would like.


Razor Edge Geometry Introduction

Posted by rwilliams on May 13, 2010

In this article, I will try to explain the characteristics of a razor’s edge geometry. For cutting tools of all kinds, edge geometry is hugely important. The wrong geometry will always result in very poor performance of any and all cutting tools.

The four elements of a cutting edge that must all work together for optimum performance at any given (coldwork) task are:

1. Hardness
2. Toughness
3. Abrasion resistance
4. Edge Geometry

Razors are “push cutting” tools. Other types of cutting edge tools may use other methods of cutting such as slicing, scoring and gouging. All these methods applied to different materials are best suited to different edge geometries. Scissors, razors and serrated bread knives all are very, very different in geometry because of the mechanical properties they need to be ideal for the task they’re designed to perform. And, of course, those properties make them rather unsuitable for other applications. Scissors and bread knives would perform poorly for push cutting beard stubble and hair from skin with minimal damage to skin and close, clean reliable cutting on the hair.

So, we’ll focus on razor geometry here. :)

And that has to start with an understanding of the task at hand. We want to cut hair from the face at or below the level of the skin on the follicle. The goal is to clear the skin of all hair doing it very close, very comfortable and with little or no damage of any sort to the skin, itself, in the process but mechanically cutting/shearing it.

Additionally, what we want out of the tool is very good edge retention so we spend much more time shaving than honing, stropping and maintaining it. This is an important consideration.

So what is a great geometry for this?

First and foremost, we need an edge with as close to zero radius as possible; no rounding or flat spots at all. This enables it to start cutting with very little pressure. The smaller the radius of the tip of the edge, the greater the shear force exerted in the smallest possible area. This enables the edge to penetrate and begin shearing very quickly and very easily. The edge must, however, widen at an angle sufficient to provide support for that cutting edge so that it doesn’t fail and deform during the cutting. The angle of the bevel on a razor blade provides this geometry. If it is too obtuse, it will not cut as easily. If it is too acute, it will fail while cutting or at the very least will not maintain it’s proper geometry for long. Generally, a bevel of around 14 to 18 degrees will be very good for this.

So, how do we know what the bevel angle really is? There’s an easy way to tell. Proper edge geometry for a razor is set by the maker and consists of a blade width that is 4 times the size of the spine width where the spine contacts the blade and the edge contacts a hone. An 8/8 razor should have approximately a 1/4″ width spine. Slightly thicker or slightly thinner would be OK but it shouldn’t vary considerably from the 4:1 ratio if the blade has good geometry; say somewhere between 4.2:1 and 3.7 to 1.



So that’s the edge geometry of a razor. Understanding this helps us understand how to hone to maintain this geometry, particularly at the very fine edge.
 

Bart

Well-Known Member
That is perfectly sound and valid information. Thank you for posting it. I usually quote 15-20 degrees for bevel angle limits, but that's pretty close to what Robert states.

We should put an article in the sharpening academy one day about this stuff.

:thumbup:

Bart.
 

Gunner777

Well-Known Member
He really has some great information on his website so it would be a great thing to add to the sharpening academy.
 

Paul

Well-Known Member
Thanks for posting this! :thumbup:

I will say that it doesn't exactly support your arguments, and I'm assuming the "real pro" comment wasn't a dig at anyone here. :)
 

Gunner777

Well-Known Member
I simply meant in the razor world he is a real pro and one of the very best custom razor makers out there. I have no reason to dig at anybody so I don't really understand the statement.If I have a problem with a person they will know it. As far as I know I have no problem with anyone.
The post was meant to help new or intermediate honers which I always like to do.
 

Paul

Well-Known Member
Gunner777 said:
I simply meant in the razor world he is a real pro and one of the very best custom razor makers out there. I have no reason to dig at anybody so I don't really understand the question.If I have a problem with a person they will know it. As far as I know I have no problem with anyone.
The post was meant to help new or intermediate honers which I always like to do.

He's a very talented craftsman, and a good friend of mine. We have collaborated on several projects, and talk regularly. He's everything you said and more. Also, there was no question, rather a statement. :)
 

Paul

Well-Known Member
Gunner777 said:
Ok I changed my post to statement.:thumbup:

Oh, well in that case, I'll explain. Words are wonderful things, vehicles of thought and all. :)

"I'm assuming that 'real pro' comment wasn't a dig at anyone here" should be interpreted to mean that I am assuming that you aren't saying that in an attempt to take a shot, or dig, at anyone here as a result of that discussion we had yesterday.

For future reference, I usually say what I mean, or if I'm "popping off", I'll usually come back and tell you what I really meant. :)
 
Top