Question about bevels

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Jason H
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Question about bevels

Post by Jason H » Thu Sep 28, 2017 5:55 pm

I have a question and am hoping to hear from the pros here. I have watched and read conflicting ideas on creating a primary and secondary bevel- I'm thoroughly confused. Why do some people create a primary bevel that is more acute than the secondary and others create a primary bevel more obtuse than the secondary? Maybe I'm missing the obvious.

J david
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Re: Question about bevels

Post by J david » Thu Sep 28, 2017 6:11 pm

Maybe I am missing something as well. Per my math, one is possible while the other is not.

RickR
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Re: Question about bevels

Post by RickR » Thu Sep 28, 2017 6:49 pm

There is contention concerning the definition of primary and secondary bevels. I've noticed that bladesmiths tend to call the first bevel they grind the primary, which makes the next one they grind, the cutting edge, the secondary bevel. Sharpeners and users tend to call the cutting edge bevel the primary, so the other one is the secondary. So your confusion is caused by this disagreement over terminology. One solution, which is slowly being adopted, is to stop referring to primary and secondary bevels, and call the bevel that is at the cutting edge the edge bevel and any bevel, if one exists above it, a relief bevel.

Jason H
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Re: Question about bevels

Post by Jason H » Thu Sep 28, 2017 9:34 pm

Well that makes sense, no wonder I couldn't envision in my mind about what they were talking about. Thanks!

Radar53
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Re: Question about bevels

Post by Radar53 » Thu Sep 28, 2017 11:53 pm

Hi There Guys, I'm probably just going to add to the confusion as I have also got caught up in the duplicate terminology. My preference, just to get away from the terms primary, secondary etc, is to try & use terms which help describe the function the bevel takes on. I often have three bevels on an edge I create.

The bevel at the edge-of-the-edge I refer to as the "micro bevel". Its usually somewhere between 0.1 to say 0.25mm wide and its at the most obtuse angle, which provides some strength & support to the edge without sacrificing much in cutting abilities.

The bevel above it, I call the "main bevel" for no other reason than that is what it is.

Finally, the tertiary or relief (there's another ill defined term) bevel is what I refer to as the "thinning bevel" or angle, because when done every 2 or 3 sharpenings, it maintains the proportions of the whole cutting cross-secction as the edge-of-the-edge creeps ever closer to the thicker part of the blade over multiple sharpenings. This is the most acute angle.

Just to confuse the issue some knives only have one single bevel, which can be quite wide & is often called a zero grind. Yeah, its a mess I think I've just added to :roll:
Cheers Grant

Just because you're not paranoid doesn't mean they're not going to get you!!

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ken123
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Re: Question about bevels

Post by ken123 » Mon Dec 11, 2017 9:28 pm

Have to agree - there are contradictory definitions in use. I specifically define the angle at the edge of the edge whether it is zero grind or a microbevel etc. It's worthwhile to specifically define the referenced bevel even if it takes a bit more effort to reduce ambiguity.

---
Ken

ChipB
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Re: Question about bevels

Post by ChipB » Thu Mar 08, 2018 12:48 am

Interesting, perhaps b/c I spend more time on the knife vs. Sharpening side of the forum, I haven’t noticed the same level of confusion. I tend to think of “grind” and “bevel” distinctly. I.E. anything that is not an edge bevel is part of the final grind and any sharpening done above the edge bevel is an adjustment to the geometry of the knife or grind profile (usually thinning). Radar, I see exactly how you are conceiving your bevel hierarchy, and it makes complete sense to me in the context of the EP. You’ve got the edge bevel (I also almost always keep it b/w 15 - 16 deg per except for rare occasions where the final grind is ultra thin and the steel is very well done), the final grind, and then any adjustments up the grind geometry. Really tough to integrate all that with the EP though. I’m a big fan of the jig, but this is one of the reasons I’m working on improving freehand

Low-n-slow
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Re: Question about bevels

Post by Low-n-slow » Sat Mar 10, 2018 11:53 am

Hello all,
New to the forums but I saw this thread and had to ask: I am finding a discrepancy with my edge pro angles on my MAC knives. According to MAC they are ground at 15 degrees but when I put them on the Edge Pro (with Chosera Stones) and use the sharpie method, I find that the angle is much steeper, More like closer to 10 degrees. I checked it against my angle cube and Phone level and they both read the same. Is this because there is a secondary bevel and its under 10 degrees and Im missing it? I just curious and dont want to hijack this thread but I thought the content was appropriate. Thanks

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Otaku19
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Re: Question about bevels

Post by Otaku19 » Sat Mar 10, 2018 8:57 pm

Are you zeroing the angle cube on the blade table and then checking the angle? 10 degrees per side seems very acute for European knives. If your reading of 10 degrees is accurate, I would set the angle to 20 degrees per side. The European steels are a little softer on their heat treat and benefit with a more obtuse angle than Japanese knives.

ChipB
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Re: Question about bevels

Post by ChipB » Sat Mar 10, 2018 11:31 pm

Agree with Otaku, 10 deg per on any gyuto is thinner than one should likely go and suspect there is hang up during measuring. Unless a knife has a perfectly flat grind/wide bevel it can be challenging to accurately read the angle of the edge bevel (indeed, many knives may not even have an edge bevel applied by the sharpener). The sharpie method could also be to blame here. Aside from numerous other issues, if the pen's tip isn't ultra, ultra thin it will tell you to take an edge that is too acute by a wide margin. In fact, I'd recommend never using the sharpie unless you have a very, very precise pen and a high magnification loupe. But if your using a loupe, you won't need a pen, so basically never use a sharpie.

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Kit Craft
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Re: Question about bevels

Post by Kit Craft » Sun Mar 11, 2018 3:12 pm

Hah, not to get things going again but you should see how the term single bevel is used on a lot of outdoor forums. Particularly the UK bushcraft forums I belong to. :D I was seriously confused when I started out on CKTG forums because EVERY term dealing with knives and their grinding seems different than what I was used to.

Now, as for the most recent question at hand. My Mac's all came with an obtuse angle at between 18-21 degrees if I had to guess, I don't measure as a freehand sharpener. They now have something that is somewhere between 12-16 degrees by my estimate and closer to 16. But 10 dps or less seems very extreme.

Radar53
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Re: Question about bevels

Post by Radar53 » Sun Mar 11, 2018 6:00 pm

+1 to what Otaku said, plus a couple of other things.
1) Generally the grind on a blade is not flat from the spine to the edge. So when using an angle cube or phone you have to ensure that you are measuring it from a consistent setup. eg if you press the edge of the knife into a flat surface and measure the angle and then press at the spine and measure a second angle they will be different so you need to be consistent. The thicker the blade the bigger the discrepancy & on a thick euro knife the difference could be 3+ degrees.
2) Secondly, the angles that are talked about are the angles relative to the centre-line of the blade (from spine to edge). So when measuring on the EP you need to zero the angle cube on the blade table of the EP, press the spine of the knife into the blade table, rest the stone on the knife edge and then measure the angle off the back of the stone in the stone arm.

There are other ways of achieving this as well, and it can all be a bit confusing for a while. Try and work through this and then come back with more questions if needs be.

HTH
Cheers Grant

Just because you're not paranoid doesn't mean they're not going to get you!!

Low-n-slow
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Re: Question about bevels

Post by Low-n-slow » Mon Mar 12, 2018 11:09 am

Thanks all! I really appreciate the advice. I will try this out and if I have any other questions Ill start another thread

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Otaku19
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Re: Question about bevels

Post by Otaku19 » Tue Mar 13, 2018 5:57 pm

Glad we could help! Enjoy the sharpening!

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