bevel angle terms

[Ken S]

I find some of the terms used for angles unclear at times. This pertains to double bevel tools such as knives. Yesterday I found words which I think solve the confusion. Steve Bottorff's Sharpening School DVD has an excellent chapter on edge sharpness theory. Steve uses the terms "half angle" and "whole angle". With a typical kitchen knife, the half angle would be fifteen degrees. The whole angle would be thirty degrees.

I have watched Steve's DVD perhaps ten times. My quiet study time is usually very early in the morning before the rest of my household awakens. Each time I study Steve's video I learn something new. Thanks, Steve for producing an excellent training program.

Ken

[grepper]

The bevel angle is the angle from the side of the blade to the cutting edge.
The included angle is the sum of both bevel angles. In general, the angle between two sides.

[Herman Trivilino]

In Tormek lingo the bevel angle ß is the angle the center line makes with the cutting edge.

The bevel angle is the angle from the side of the blade to the cutting edge.

That matches Tormek lingo when the sides of the knife are parallel. However, if the sides of knife are not parallel then the Angle Master will not correctly measure the Tormek bevel angle. This is one reason why the kitchen knives I buy all have parallel sides, all the way to the cutting edge.

The included angle is the sum of both bevel angles. In general, the angle between two sides.

This is what I call the edge angle. It will not equal the sum of the two bevel angles as you've defined them, but it will if you use the Tormek definition of the bevel angle.

And doubling the bevel angle to get the edge angle works when the bevel angles are equal.

[Herman Trivilino]

Steve uses the terms "half angle" and "whole angle". With a typical kitchen knife, the half angle would be fifteen degrees. The whole angle would be thirty degrees.

Then the half angle equals Tormek's definition of the bevel angle. Note the Angle Master will give you this angle only if the sides of the knife are parallel.

The notches on the Angle Master will give you what you are calling the whole angle. What I call, and what Tormek calls, the edge angle.

Note that on a typical wood chisel the bevel angle equals the edge angle.

The rule I remember is that the sum of the bevel angles equals the edge angle. This is consistent with the Tormek definitions of these terms.

[Jan]

I find some of the terms used for angles unclear at times. This pertains to double bevel tools such as knives. Yesterday I found words which I think solve the confusion. Steve Bottorff's Sharpening School DVD has an excellent chapter on edge sharpness theory. Steve uses the terms "half angle" and "whole angle".

Ken

Ken, thanks for drawing our attention to Steve's denominations. The terms "half angle" and "whole angle" are intuitively clear. Similarly the term "included angle" mentioned by Grepper.

Tormek however recommends and consistently uses the terms "edge angle" and "bevel angel". 

Jan

[Jan]

That matches Tormek lingo when the sides of the knife are parallel. However, if the sides of knife are not parallel then the Angle Master will not correctly measure the Tormek bevel angle. This is one reason why the kitchen knives I buy all have parallel sides, all the way to the cutting edge.

Herman, I fully agree with your important note. 

Since I know about this AngleMaster issue, for all knifes which taper from the spine to the edge, I set the bevel angel using the kenjig. 

Jan

[Elden]

   I like that Ken and Steve. To me, it requires no memorization.  Yes, that memorization should not be a large hurdle to accomplish.

[Ken S]

Realizing that formany of our members English is a secondary language, I try to explain English idioms or avoid them. In this case, the English idiom "hit the nail on the head" meaning to address the issue quite correctly comes to mind. Elden and Jan, you hit the nail on the head. I was looking for terms which required no memorization; words which are  intuitive.

I certainly understand the preference for using standardized Tormek terminology. I will try memorizing them. At this point they are not yet intuitive for me. I am also concerned with writing for new users. In the words of a wise retired woodshop teacher I know, I want words which are "stone simple" meaning direct and not confusing. I am not as math fluent as Herman and Jan. I appreciate the value of more exact and mathematical terminology and am in process of developing that fluency.

At the risk of being ken and recommending the kenjig (if you recall, I originally called it the KS-150 but started a renaming contest for it to avoid confusion with official Swedish jigs), I think the kenjig is the quickest most accurately repeatable method of setting knife angles. The black market would be the second most convenient method. I find the anglemaster better suited for chisels and bench plane irons. Jan's point is well taken.

I almost included something about knives with two separate bevel angles in my original post. I left it out for simplicity. I do not presently have any knives with different bevel angles. I also have not put any double bevels on my bench plane blades. (Double bevels on plane blades raise thebevel angle to assist in planing exotic and highly figured wood. I use only more garden variety in my humble woodwork, although I believe a well trained sharpener should be aare of such things.) I believe I would handle knives with didderent bevel angles with two kenjigs, one for each bevel angle. Being able to sharpen these knives accurately and efficiently should increase a professional sharpener's prestige and profit.

Like Herman and most of us, I live in the simpler matching bevel world.

Thanks, all, for sharing your thoughts.

Ken