Razor Blade Sharpness Chart

Bogeyman said:
This man's testing and charting of such just blew me away!! His summaries are spot on IMO and his opinions virtually match mine based on blades I have used that he has tested. Now I know even better why I like the blades I like. ;)


https://www.refinedshave.com/razor-blade-sharpness-summary/
Click to expand...

A noble attempt to provide some assessments of blades from a scientific basis.

There was a great thread on B&B where a user took photos under 150 times magnification and the results were fascinating; it was clear to see which blades had the most clear and precise grinds. Sadly that particular thread has been robbed of it's images after the demise of Photobucket.
 
I must be reading this wrong, because Derby is shown sharper than Feather???

P.S: He measures sharpness by measuring "force", which he measures in grams??? Grams measure weight, not force. Besides, the way he measures, dont' take into account blade flexibility, blade thickness, mass and lastly that the blade isn't straight in a razor, it's bent and the final sharpness depends greatly at what angle the bent blade will encounter the hair.

Finally, about measuring "force". F = mxa (Force=mass x acceleration). Thus measuring grams, you are not measuring force. (i mean, Newton was british, wasn't he?)
 
Measurement of blade sharpness in the factory, done by measuring force while cutting paper, at around 3:53.

As you can see, the measurement doesn't measure grams, which would be supersimple, wouldn't it? Why have a separate analyzer, when you can just put a cheap scale and measures grams... Because the scale measures weight, not force. And force isn't a measure of sharpness either.

And here's how it should be done, in confirmation of how Croma's video above does it:

http://www.catra.org/pages/products/razors/redst.htm
 
Technically you're correct about the unit of measurement, however a force gauge works in exactly the same way as a scale it just displays the result in a different unit. Not surprising really considering that weight is merely the measurement of force exerted on a mass by gravity.

Without having a force gauge to hand a scale will perform just as well if all you want is a relative measurement.
 
Shave to the grave said:
It makes for an interesting read but blade sharpness is a very subjective thing.
Click to expand...

There is an absolute sharpness, which can be measured by equipment and a relative sharpness, which is very subjective, because depends on the only measurement sensor each one has, our beard and skin. For instance, someone with soft beard, will find Derby a sharp blade and probably every other blade more or less equal. Because it becomes like shooting a fly with a small cannon vs with a large cannon. In both cases, for the fly, it's "too much".

On the contrary, a machine can give absolute sharpness ranking, because the measurement doesn't contain subjective factors. The "stubble" is the same for all blades tested.
 
chris.hale said:
Technically you're correct about the unit of measurement, however a force gauge works in exactly the same way as a scale it just displays the result in a different unit. Not surprising really considering that weight is merely the measurement of force exerted on a mass by gravity.

Without having a force gauge to hand a scale will perform just as well if all you want is a relative measurement.
Click to expand...

We have gone from trying to measure sharpness, to measuring force, to measuring weight, to gravity.

1) Sharpness isn't measured by force.
2) F = mass x acceleration (Newton's 2nd law). Measured in Newtons, alias kg x m/sec.

A scale measures in kg. Hence, it doesn't measure force. Even if it measured force, as seen in the link above, for sharpness they measure Force in relation to cutting depth.

Unless, one wants to believe that Derby is sharper than Astra or Feather, at which point, i rest my case. :D
 
Obelix said:
A scale measures in kg. Hence, it doesn't measure force
Click to expand...

If I may draw your attention to definition 2 below, you'll see (that's) exactly what it does do.

weight

[weyt]
See more synonyms on Thesaurus.com
noun
1.
the amount or quantity of heaviness or mass; amount a thing weighs.
2.
Physics. the force that gravitation exerts upon a body, equal to the mass of the body times the local acceleration of gravity:commonly taken, in a region of constant gravitational acceleration, as a measure of mass.
3.
a system of units for expressing heaviness or mass.
 
chris.hale said:
If I may draw your attention to definition 2 below, you'll see (that's) exactly what it does do.

weight

[weyt]
See more synonyms on Thesaurus.com
noun
1.
the amount or quantity of heaviness or mass; amount a thing weighs.
2.
Physics. the force that gravitation exerts upon a body, equal to the mass of the body times the local acceleration of gravity:commonly taken, in a region of constant gravitational acceleration, as a measure of mass.
3.
a system of units for expressing heaviness or mass.
Click to expand...

So your reply to physics is...dictionary? Then, pray tell, why is force measured in Newtons and not in kg?

This is why:

https://en.wikipedia.org/wiki/Mass_versus_weight

What does this have to do with measuring sharpness by weight? Nothing. Does measuring weight equals to measuring force? No. The weight is only the particular force the earth exerts on everything on it. What does this have to do with a blade sharpness of cutting force? Nothing. So Isaac Newton's reputation can live another day.
 
BoldSpice said:
Yes, you're reading it wrong.
Click to expand...

Either way i try to read it, since there is no visible explanation next to the chart, "i am reading it wrong". Because in any case, Derby is sharper than Astra or if i read it the opposite way, sharper than Feather.

At any case, everyone is free to believe what he wants.

Derby Extra
(Green) 53 44 51 49
Astra
Superior Platinum 49 46 44 46

So, assuming that lower number is sharper, in shave 2, a Derby is sharper than Astra in shave 2. Then Derby becomes duller, slightly so.

Similar to Astra, which starts duller, gets sharper, sharper. So shave 3 is the sharpest in the Astra and overall they are very close to sharpness with Derby.

It's a theory...

EDIT: Wow, i noticed Kai blades are so similar to Derby! And to imagine that people claimed it's Feather-like!

EDIT 2: Also it seems almost all blades, are sharper after shave 3, than they were in shave 1. Amazing... I would have expected them to be duller.
 
Last edited:
Obelix said:
So your reply to physics is...dictionary? Then, pray tell, why is force measured in Newtons and not in kg?

This is why:

https://en.wikipedia.org/wiki/Mass_versus_weight

What does this have to do with measuring sharpness by weight? Nothing. Does measuring weight equals to measuring force? No. The weight is only the particular force the earth exerts on everything on it. What does this have to do with a blade sharpness of cutting force? Nothing. So Isaac Newton's reputation can live another day.
Click to expand...

OK, so in the second part of your post you have finally acknowledged that weight is a measure of the FORCE the earth's gravity exerts upon a mass. Walking you gently through this, the scale is measuring that FORCE.

As you correctly point out, weight is referring to one specific force, gravity (or at least its effect on a mass), which is why newtons are used for measuring force in other scenarios. As the gravitational force on a 1kg mass on Earth is 9.8 newtons, you could attach your kitchen scale to the wall, press on it with your hand, and when it reads 1kg you're exerting approximately 10 newtons of force on it. 2 kg = roughly 20 newtons. This is how a scale can be used to measure force even though it reads in KG and not newtons. All a force meter is is a scale calibrated to display in newtons.

The amount of force required to push a blade through a consistent medium can be taken as a measure of its sharpness as a sharper blade will cut through more easily, hence if a blade requires 1 newton of force to cut through 1cm of medium, and another blade requires 5 newtons of force to make the same cut, the conclusion can be drawn that the blade which requires less force is the sharper of the two. This is how force can be used to compare sharpness, and how a scale calibrated in KG can be used to measure force.

I've done my best to clarify this, but if you're still not following I don't think I can help.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom