Thread: Tape

Wowza.....you'se guys is killin me......I'm ok with the 15 to 17 degree angles and these are basically based on the razor geometry itself in any case. Please keep measuring......lol. I have used the Chromium for years off a leather flatbed hone without any of the problems discussed here. I have also used it on paper over a glass flatbed and then with the edge into it vs. the stropping stroke and again no problem. The amount of strokes being advocated is excessive in my unlearned opinion, but as always, I bow to your expertise. Randy who.............

Lynn

Randy Tuttle for every time I mention a Randy in a honing-related discussion
As for the number of strokes.. Well, many people do about 10 strokes on 1.0 before doing another 10 on a 0.50. I just do 20 on 0.50 instead and there are no adverse consequences.

Oh well.......I don't use the 1.0 either.......and I still don't do more than 10 strokes on the .5 but I can't be honing anywhere near as many as you. The part of all this is what causes all the confustion for new people. This stuff is not mystical but a process and nobody's word is gospel no matter how much they post. There are some basics that work most of the time and get people started and then it's getting to know all the different blades out there and then how the condition of the blades effect the honing.

You guys have fun.....I'm done with this one.

Lynn

Most of this is just experimenting around with the hones and pastes. When I leave the 15k Shapton I only give the razor about 5 laps on the chrome oxide paddle. But for touch-ups I don't usually want to haul out the Shapton while I'm standing there lathered up so I grab the paddle and I may well do 20 laps or so on the chrome oxide paddle, depending.

Unfortunately I've got pretty acidic skin: most jewelry starts dissolving on me within hours unless it's high-quality stainless or high-carat gold*, and this seem to be the big culprit for my razors as well. I can get two weeks** on an edge, whether I use it every day or use it once and put it away. But once I use and edge its days are numbered.

*Chrome-plated digital watches do better, but they corrode internally before my skin bubles the metal under the chrome. Stainless steel mechanical watches seem to survive because the jewel bearings insulate the important moving parts. So all my watches are stainless mechanicals.

**stainless razors are more like two months. I really like my Friodurs and Puma INOX razors.

Added a 8/8 W&B "Celebrated" to the angle measurements post.

Originally Posted by mparker762

Unfortunately I've got pretty acidic skin...I can get two weeks** on an edge, whether I use it every day or use it once and put it away. But once I use an edge its days are numbered.

Interesting, I've never heard of this sort of thing before. If you rinse, dry, and oil your blades after use is this still true?

In a PM to Lynn I handwaved off any error from the lack of right angles. I apologize, it's been a long time since I've done this for real and I didn't want to calculate chords on the curve the the honing flat makes as you sweep it around the fin of the blade, and I knew that my original calculation was understating the actual angle a bit. I smacked my head this morning when I realized I was being stupid, I simply had to correctly use the blade width measurement as the tangent and half the spine thickness as the sin and everything becomes simple again. The correct calculation is 2 x ASIN((spine thickness/2)/blade width), which gives you the correct right angle needed for the calculation. The asin calculation gives you the angle for one half of the blade. Corrected figures below...

Originally Posted by mparker762

Nope, that's in the ballpark. Most razors I've measured have been between 15 and 19 degrees.

First three I grabbed at random:

5/8 Clauss Barber's Special (mint):
0.65" by 0.18".
ATAN(0.18/0.65) = 15.5 degrees

The correct value is 2 * asin(0.09/0.75) = 15.9 degrees

Originally Posted by mparker762

6/8 Henckels Friodur (new, honed once):
0.75" by 0.24".
ATAN(0.24/0.75) = 17.74

The correct value is 2 * asin(0.12/0.75) = 18.4 degrees

Originally Posted by mparker762

6/8 Robeson Shuredge (NOS, honed once):
0.73" by 0.23"
ATAN(0.23/0.73) = 17.48

The correct value is 2 * asin(0.115/0.73) = 18.1 degrees

Originally Posted by mparker762

8/8 Wade & Butcher "Celebrated Razor for Barber's Use":
0.97" by 0.31"
ATAN(0.31/0.97) = 17.72

The correct value is 2* asin(0.155/0.97) = 18.4 degrees

Originally Posted by mparker762

For computing the angle, only the distance from the edge to the wear mark on the spine matters. If you mistakenly measure from the edge to back of spine then most of these wind up in the 12-15 degree range.

I apologise for the error.

Yea, ummmmmm thats just what I was thinking . . . either that or "holly cow this is getting complicated."

Are you saying you're dividing the Blade thickness by the height measured from where the shoulder hits the hone and then hitting your tangent button??

Lynn

The calculation needs right angles for correctness.

You can think of the blade as an isosceles triangle described by the edge and two honing flats, with the two sides of the blade as equal length, and the base of the triangle being the distance across the flats. If we divide this into two triangles, one for each half of the blade, then we get a right angle between the line down the center of the blade and the line between the two honing flats. We know the distance between the honing flats - that's the thickness of the blade, so half of that gives us the length of the short end of this right triangle. The length of the long side of the triangle is the width of the blade from edge to honing flat. Given the length of two sides of a right triangle we can calculate the third side (using the pythagorean rule) or any angle in that triangle. Let me see if I can draw an ASCII picture:

Code:

     h  /|  (T)
    t  / |   h
   d  /  |   i
  i  /a  |   c
(W) -----|   k (T)
  i  \a  |   n
   d  \  |   e
    t  \ |   s
     h  \|   s

The width of the blade is W, the thickness at the spine is T. The angle that's easy to compute is "a", half the angle of the blade. Since we know W (the width of the blade along the side) and T (thickness of the blade), and the height of this half-blade triangle is half of that (T/2) we can calculate the angle "a" by the inverse sin function ASIN( (T/2) / W). But this only gives us half the angle of the edge, so we multiply that by 2 for the final answer.

The differences between the inverse tangent, inverse sin, and inverse cosine functions are that they calculate the angle "a" using different sides of the triangle. Inverse cosine would be used if you knew the blade width across the side of the blade and the blade width through the center of the blade, and inverse tangent would be used if you knew the blade thickness and the blade width through the center of the blade. In this case we know the thickness of the spine and the width along the side of the blade, so we need the inverse sin function. On a calculator these functions are represented by ASIN, ACOS, and ATAN, or sometimes as SIN-1, COS-1, and TAN-1 (where the "-1" is an exponent).

Edit: It just occurred to me that some of the confusion over the blade angle may be because I'm calculating the full blade angle, whereas knife guys generally talk about the half-angle, since this is what they set on their honing jig if they're using a Lansky, or eyeballing the angle between the knife and stone if they aren't. So if you want to compare these numbers to knife angles, don't multiply the ASIN value by 2....