My appologies for such a simple question, but an answer is fundamental to me.

T

Thonord

Joined
May 10, 2012
Messages
5
I have searched, but there is simply to much information available to create a "Search" for basics.

So, please bear with me, for I see no purpose in attempting to sharpen a knife until I understand "an angle".

8511366982


Sorry, I need to pause here. I have to check if the image becomes visible. It does nor do so by previewing.

Edited:

Well, no image. I need it to support the question.

Please disregard this thread.

Edited:

http://www.flickr.com/photos/7302939@N06/8510387697/in/photostream

Edited: Alright! A link that works.

So, my question: Recognising that the 20/15 degrees double bevel is suitable for my chef's knife, is the included angle C-e'-D 20 degrees, or is the edge angle C-e'-F 20 degrees?
 
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All you have to do to post a pic is start a photo bucket account and post a link to the image......
 
Thanks 9blades. I have a Flickr account and I asume it will work.
If not, I'll create an acount on photo bucket.
 
That pic is somewhat confusing and seemingly over-complicated. But, as it's labelled, it would seem to imply the included angle of what it labels as 'primary' ('CD') is 20°, or the sum of the 'edge angles' of each side (presumably 10° each). The angle labelled as 'relief' ('AB', though the 'B' appears obscured) in that pic appears to be 15° included (7.5° per side).

Managed to finagle a way to link the pic here:
8510387697_93a394fb63_z.jpg



David
 
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Weird notation in the figure, but what you probably want at this point is 15/20 per side (C-e-F = 20 degrees), which is 30/40 inclusive (see the little picture in the corner).
 
mtangent said:
CeF is 20 deg, not CeD.
Click to expand...

Thanks mtangent.
Exactly my point.

I have come across several references to the 15/20 and thought I understood it, but then I came across the drawing (the red stuff is mine to make my point). I also read the CeD in the drawing drawing to be 40 degrees and not 20 as written, but I am a total Newb.

So, to what angle do I lift the back of my kitchen knife, from a horizontal bench stone, to - first grind the 15 relief and then the 20 bevel?

Personally, I think 7.5 and 10 degrees, but thats just because I don't think a 40 degree edge can be sharp. If I lift the back of my knife 15 and 20 degrees the edge will be 40 degrees.
 
Thonord said:
So, to what angle do I lift the back of my kitchen knife, from a horizontal bench stone, to - first grind the 15 relief and then the 20 bevel?

Personally, I think 7.5 and 10 degrees, but thats just because I don't think a 40 degree edge can be sharp. If I lift the back of my knife 15 and 20 degrees the edge will be 40 degrees.
Click to expand...
Yes, you'll want to lift the back about 15 degrees. Then you can, optionally, lift it a little higher for a micro bevel. you could also try and leave it at 15 per side and hold off raising the angle until you see how the edge holds up. Forget that picture. The edge angle in the figure is drawn at about 70 degrees inclusive (35 per side). Your edge won't look like that. Also, the sides of your blade won't be parallel like that.

The general recommendations you've seen that say 15/20 refer to 15/20 degrees per side. I guess some recommendations have mentioned the Spyderco Sharpmaker. The sharpmaker uses 15/20 per side (30/40 inclusive).
 
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mrdeus said:
The general recommendations you've seen that say 15/20 refer to 15/20 degrees per side. I guess some recommendations have mentioned the Spyderco Sharpmaker. The sharpmaker uses 15/20 per side (30/40 inclusive).
Click to expand...

OK, that makes sence.

Maybe the text in the drawing CD = 20, means angle C=20 degrees and angle D=20 degrees. And consequently angle A= 15 and B= 15.
 
Obsessed with Edges said:
As the pic is labelled (verbatim), 'Angle CD=20 degrees'. Seems odd, and probably should be wider, based on the appearance of the drawn angle. But, there it is.


David
Click to expand...

I agree. Hence the general confusion around angle statements and drawings. They are sometimes contradictory and mis-labeled. This adds to the confusion for noobs.

Thonord said:
Thanks mtangent.
Exactly my point.

I have come across several references to the 15/20 and thought I understood it, but then I came across the drawing (the red stuff is mine to make my point). I also read the CeD in the drawing drawing to be 40 degrees and not 20 as written, but I am a total Newb.

So, to what angle do I lift the back of my kitchen knife, from a horizontal bench stone, to - first grind the 15 relief and then the 20 bevel?

Personally, I think 7.5 and 10 degrees, but thats just because I don't think a 40 degree edge can be sharp. If I lift the back of my knife 15 and 20 degrees the edge will be 40 degrees.
Click to expand...

I think you are right. As you say, using the terminology in the drawing, lift 15 degrees for relief and 20 for primary - that's my interpretation anyway.

Thonord said:
Yes, but I think the drawing is explanatory and not to scale.
Click to expand...
Definitely not to scale. Most of these types of illustrations are no where near accurate in their representation of angles. I think that just adds to the confusion.

mtangent said:
CeF is 20 deg, not CeD.
Click to expand...
.
 
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