Thread: How do not make it worst?

Originally Posted by gssixgun

Here is the math


(2 * asin(w / (2 * h)) * 180) / pi = a


w = Width of the spine
h = Height of the blade
a= Bevel angle


Plug in the original then subtract the depth of the largest chip and figure for after grinding

We know that razors are shaving from 12° - 23° from when we did the measurements on our razors, so if it falls inside there, life should be sweet, if not then you need to wear down the spine some too...


ps: I have never linked that vid to this forum in the past because of the negative connotation to breadknifing, so as the warning on the vid states "Use at your own risk" it is not the technique that is lacking if you can't get your razor sharp again it is your skillset....

Ok Glen, what do you do for a living? Are you a physics teacher or something? That equation just blasted my mind! You'r level of wisdom boggles my mind some times!! In a good way!

(2 * asin(w / (2 * h)) * 180) / pi = a

Ok, just to put this in words. What I'm reading says "Two multiplied by the arcsin of (blade width divided by twice the blade height, then multiplied by 180), then divided by 3.14 equals the angle I hope is equal to 17-22 degrees.

Anyways, to the OP, a smart fellah once told me that if you go into the edge too deep, you're likely to hit "durable" metal, which won't take an edge no matter how hard you try. I won't give his name, just in case my understanding of what he said is screwy. At any rate, I think you'll do fine grinding it away on your DMT. And then being very patient on hones. But if you can do the math, it would get you there sooner probably. Having a goal always helps you get there faster than just sitting down and saying, "I'm not getting up til it's sharp."

Originally Posted by HARRYWALLY

Ok Glen, what do you do for a living? Are you a physics teacher or something? That equation just blasted my mind! You'r level of wisdom boggles my mind some times!! In a good way!

No Gugi and Hoglahoo posted the Math long ago you don't need to do anything other than simply plug that formula into Google and Voila' magic happens

The hope is to hit as close to 16 as possible, that is the mean average bevel angle we found,, BUT there are razors out there that shave fine with bevel angles between 12 and 23... The majority by a very large amount fell between 15 and 17...

Here is a thread where the formula is used
http://straightrazorpalace.com/advan...-theories.html

Also about the "Belly of the blade" theory, honestly I agree with this to an extent, however there are way to many old razors that are well worn into the belly of the blade (durable area) that simply keep right on shaving... This flys directly in the face of the theory
I would agree that the shaves may have a different feel to them but I would not go so far as to say they are no good when worn into the belly

It's too bad about that blade, makes you wonder what the previous owner was using it for?! Hope you figure something out, because I sure love them scales.

I think it was never used. I think it was taken out of the box, damaged and put back to the box. I looked closely. It was stored in good home for many years. no rust, no sign of use. Blade looks like from factory. No spine wear. The only job I did was to clean up the scale. Now honing. I hope it will come OK. Glen actually did breadkinifing on one of my razor. Come out great... but he is a champ :-) Me-just still learning :-)

Originally Posted by Firefighter2

It's too bad about that blade, makes you wonder what the previous owner was using it for?! Hope you figure something out, because I sure love them scales.

Originally Posted by gssixgun

No Gugi and Hoglahoo posted the Math long ago you don't need to do anything other than simply plug that formula into Google and Voila' magic happens

The hope is to hit as close to 16 as possible, that is the mean average bevel angle we found,, BUT there are razors out there that shave fine with bevel angles between 12 and 23... The majority by a very large amount fell between 15 and 17...

Here is a thread where the formula is used
http://straightrazorpalace.com/advan...-theories.html

Also about the "Belly of the blade" theory, honestly I agree with this to an extent, however there are way to many old razors that are well worn into the belly of the blade (durable area) that simply keep right on shaving... This flys directly in the face of the theory
I would agree that the shaves may have a different feel to them but I would not go so far as to say they are no good when worn into the belly

I'm curious. What is the "durable metal" theory? I can see the blade being more tempered at the edges to allow for easier sharpening with the metal being harder as you leave that area but that wouldn't equate to not holding an edge. It would just be more difficult to get there.

What am I missing?

Originally Posted by gcbryan

I'm curious. What is the "durable metal" theory? I can see the blade being more tempered at the edges to allow for easier sharpening with the metal being harder as you leave that area but that wouldn't equate to not holding an edge. It would just be more difficult to get there.

What am I missing?

The way I have heard it told is that, the hardening is the other way around actually, ie: the edge is hardened better to hold the edge and as you move higher into the belly the steel is softer so it doesn't hold the edge..

Also there are different grinds that change this whole equation totally, two that come to mind are the Bellied Hollow and the Double Grind on either of those logic tells us something has to change as there is a definite thickness variant at about 1/8 inch from the edge..

However as I said above there are tons of well worn razors that are deep into the belly and they still shave

An simpler formula to calculate your bevel angle is

a=2(arctan({0.5x]/y})

a = bevel angle
x = spine width
y = blade width

Eh! Breadboard the hades out of it until you get a flat line. Like an airport runway!
Put a layer of tape on the spine and run it up and down a DMT 325 for 50 laps. Put another layer over that worn layer and go on the DMT until the runway diappears into oblivion. Change the outer layer often, but leave the inner layer be.
Once you get the edge invisible, go to a 1000 and spend the afternoon! Then, you will have something to hone which will work. Just keep the bottom layer of tape as-is and change the top layer thru the 1000. I never have tape wear below 1000 to appreciate. If the edge is to be kept smiling, this is how I would do it. (mebbe a 3rd layer?) JMHO, YMMV

About the "durable metal" statement, Glen is pretty much on the right track. Back in the day before "high carbon" ( I use the term loosely ) was invented, iron was hardened by a process known as case hardening.

The piece to be hardened was wrapped in leather and then placed in somewhat airtight (I'd bet they learned the hard way to leave a vent in it and it probably didn't take but one explosion of hot metal to teach them) container. The whole thing was heated to cherry red. During this process the leather would carbonize and the iron would absorb some of the carbon. The carbonized layer was rarely very thick as you can imagine. It was harder than iron. It was also somewhat more brittle.

I'm thinking that the "durable metal" would have been the iron below the case hardened layer. I'd also think that probably refers to cutting instruments made before the 19th C.

End of lecture, class dismissed.