Clearing up Confusion over Knife Bevel Angles

[Rob]

Hi Folks

I've noticed a number of posts recently where we're getting our wires crossed with two things related to knife bevel angles:

1) The terminology - specifically the notion of "included angle" versus "bevel angle"
2) An appropriate angle setting for sharpening depending on the job the knife is to perform

My sense is its worth a post to try and develop this so we can do two things: have a common language so we understand one another and maybe if it ends up as a definitive piece - a summary for the learners sticky.

The problem is clear - multiple input sources name things differently.  We now have inputs from Tormek, Jeff, the forums own experience, Ron Hock and the CEO of Lee Valley Tools to name the obvious ones.

So here's my attempt to run it up the management flagpole....see what drops out

Included Angle

This is the sum of the two bevel angles (naturally it is only relevant in double bevel knives) ie if a bevel angle is 10^o then the included angle is 20.  Critical to defining which angle you grind to of course.

Whats the right angle for the job?

My personal view out of the sources I've come across....the Leonard Lee approach from "The Complete Guide to Sharpening" Taunton Press.  The only reason I choose this is because out of all the editorial I've read...he makes the most sense to my intuition.  Mr Lee has this to say (incidentally I use his kitchen knife angles every day in my kitchen and it works for me)

- The practical test of sharpness for a kitchen knife is if it will slice bread, meat, soft veg.
- since these materials exert minimal forces on the cutting edge, you do not have to police your bevels very closely.
- You can sharpen most at bevel ranges from 5 to nearly 20 (10 to nearly 40 included) without being overly concerned about edge retention.
- Great flexibility resides here and within this range whats right for you is what you feel comfortable you can consistently achieve
- exceptions exist for knives that are destined to chop, cut through bone, divide frozen meat etc ie have to work harder then slicing
- for chopping he recommends included of 30deg, for cleavers 50deg

So in short the principle is clear....a yielding substrate (tomato etc) requires only a fine angle.....the more resistance the substrate offers the more obtuse the angle should be.

So once on to pocket knives etc that are out of the kitchen and cutting all manner of things from fishing line to stripping the bark off a willow stick to make your sons first bow and arrow.....over to you.

What would be helpful at the end of this is a short summary table something like

Knife type          Bevel Angle          Included Angle

kitchen slicing         5                        10
Kitchen chopping     15                      30
Kitchen cleaver        25                      50
pocket knife            20                       40
Fish filleting knife    5                         10

etc                         

[Ken S]

Good thoughts, Rob.

Leonard Lee was a Canadian government worker who started a very small tool business over a kitchen table conversation with Gary Chan, the owner of Garrett Wade.  Fast forwarding, he has turned over the day to day operations of that business, Lee Valley (and the manufacturing arm, Veritas) to his very capable son, Robin.  His semi "retirement" job is running a related business he established designing and manufacturing specialized surgical instruments.   He grew up on a farm in western Canada, and is no stranger to using sharp tools including azes.  He has a wealth of tool knowledge. I also find his dry and candid humor refreshing.  (Enjoy it in the DVD on sharpening he did sold by Lee Valley.  It, and his fine book should be part of all of our personal libraries.)

Another off shoot of Garrett Wade is Thomas Lie-Nielsen.  He was working in the sales department of Garrett Wade when a favorite plane was discontinued.  He moved back to Maine and set up shop in a converted chicken coop to manufacture that plane.  The rest is history.  By the way, his sharpening book should also be part of our libraries.  (I am embarrassed to admit that although I have read it, I have not yet purchased my own reference copy.) 

Ron Hock is a knife and blade maker of lifelong experience. He has been an early pioneer in premium replacement blades for planes and scrapers.  His book is a must have for us.  He writes an interesting and informative blog.

Lie-Nielsen has produced quite good you tubes demonstrating use and sharpening of their tools.  So have Lee Valley and Ron Hock.  All are well worth our time in exploring.

Jeff Farris certainly needs no introduction here.  While most of us are various levels of beginner to intermediate in some areas, Jeff has been demonstrating and trouble shooting the Tormek for many years.  While some of us (myself included) have fairly solid educations in parts of this work,  Jeff is a long time veteran of many campaigns in the trenches.  We are most fortunate to have him and his expertise.

I am certain there is much expertise and experience at Tormek.  Some of that I have seen and some I take on faith.  I would like to see more training material from Tormek.  The new you tubes are a definite step in the right direction.  There is room (and a need) to grow.

I also believe there is value in this forum.  That value will continue to be directly related to our desire to expand our knowledge and proficiency.

I am positive about the future.

Ken

[Rob]

Thanks Ken

I should add that In Leonard Lees chapter on knives he stipulates that he free hands his own.  For our purposes I don't think that's particularly relevant. Reason being that one of the driving thirsts behind this forum is the desire to get a very refined repeatable bevel.

I think Tormek have set the benchmark with their jigs in that respect. Other home made jigs have also facilitated a much simpler path to that nirvana of a known and repeatable bevel angle on a small knife.  Free handing does work for sure, but you can't control the bevel angle to anything like the extent you can with a jig.  So I've omitted that bit of his text in case anyone wonders where it went

I also omitted but its probably worth mentioning his recommendation for soft slicing ie meat, bread etc.  He actually advocates an ever so slightly serrated edge (at the microscopic level).  You've all cut a tomato with a sharp serrated knife and know how well it seems to part the skin, he's taken that to science degree level. He advocates honing between 800 and 1200 on a water stone which puts a "bit of tooth" on the edge to use his words. This puts us in great shape for the Tormek tuned to 1000 grit

I love the idea that ground at 1000 grit, the blade has a "bit of tooth" :-)

Anyway, I appreciate this might be deemed too detailed but it seems worth mentioning to me

[Rob]

Perhaps master blade smith Bob Kramer can guarantee his 12deg freehand but for the rest of us mere mortals...

[Herman Trivilino]

Ron, what you are calling the included angle, along with many others in the literature, Tormek refers to as the edge angle.  I have tried to consistently use the terms bevel angle and edge angle in my posts, not only to be consistent with the Tormek literature, but because I find them more meaningful.  The bevel angle is the angle of the bevel, and the edge angle is the angle of the edges.

I find it interesting that multiple sources seem to be recommending a bevel angle as small as 5^o.  We can't measure that with the Tormek Angle Master, and I can't reach it with my homemade jig.  I'm pushing it to get 10^o because at that angle the blade has to extend past the edge of the platform by a significant fraction of it's total width.  It may be possible to modify the jig to accommodate a 5^o bevel, but it would be of practical use at that angle only for wider blades such as the blades of some kitchen knives.

Ron Hock also states that he free hands his knives.  I think many professionals, if not most, do it this way.  The 10 000 hour rule applies here.

[grepper]

I can't figure out what your problem is Rob.  I mean, according to Master Blade Smith Bob, it's "Very easy and accessible"!

Yea.  Maybe with 10 years of practice!

I've got to agree with that "bit of tooth".  For general purpose kitchen knives I do 1000 grit, and even sometimes less, and then don't generally hone them.  That little bit of tooth makes a big difference in breaking that oddly tough tomato skin, onion skin and bread.

One year here was pretty droughty, and the poor tomatoes suffered.  By the time they ripened their skin was extremely tough.  The only way to slice them with a smooth edged knife was to pierce the skin with the tip first.  I didn't have the Tormek then.  Now I'm hoping it will happen again as it will be great for testing different edge types!

Maybe I'm just a rather insensitive clod, but for kitchen and general use knives I really don't notice a 5 ⁰ bevel angle difference.  I have not really experimented, but I'm not sure I'd even notice the difference between 10 or 20 degrees!   If it's good and sharp.., that's what I notice the most.

[Rob]

Ron, what you are calling the included angle, along with many others in the literature, Tormek refers to as the edge angle.  I have tried to consistently use the terms bevel angle and edge angle in my posts, not only to be consistent with the Tormek literature, but because I find them more meaningful.  The bevel angle is the angle of the bevel, and the edge angle is the angle of the edges.

I find it interesting that multiple sources seem to be recommending a bevel angle as small as 5^o.  We can't measure that with the Tormek Angle Master, and I can't reach it with my homemade jig.  I'm pushing it to get 10^o because at that angle the blade has to extend past the edge of the platform by a significant fraction of it's total width.  It may be possible to modify the jig to accommodate a 5^o bevel, but it would be of practical use at that angle only for wider blades such as the blades of some kitchen knives.

Ron Hock also states that he free hands his knives.  I think many professionals, if not most, do it this way.  The 10 000 hour rule applies here.

Herman

That's interesting. This is precisely my point....the terminology is confusing. So for you...edge angle and included are synonyms but all sources agree on bevel.

You see to my mind edge is more confusing than included because included suggests more than one angle is in play. Edge on the other hand is ambiguous ie which edge?

So personal preference would be included but you've obviously been careful in choosing your terms given you've referenced Tormek so you're equally correct. Thus its important we now understand these terms are synonyms and interchangeable.

As to the low as 5deg point on kitchen knives, I couldn't agree more. I've seen many references to ultra fine angles. But as you rightly point out....the jigs struggle to achieve that.  This is another reason I like Lee's perspective ie a range from 5 to 20 is ok because he's practical minded about it. He says just hone at the angle that works best for you (within that range).  I have to say, the more I read about kitchen knives the more I'm inclined to think of these sub 10deg angles in the same way as those expensive salon scissors.......ego maybe the driver. All the authors that have credible authority in the tools world seem to agree that a range is permissible within that tolerance and that the angle isn't critical ( because meat, veg, bread pose little resistance to the edge)

[Herman Trivilino]

That's interesting. This is precisely my point....the terminology is confusing. So for you...edge angle and included are synonyms but all sources agree on bevel.

Yes, but this is the Tormek forum.  Newbies coming here, and experienced users too for that matter, are looking for information that clarifies and goes beyond what's found in the Tormek manual and other Tormek literature.  To my mind it'd be better if we use the same terminology as Tormek uses. 

You see to my mind edge is more confusing than included because included suggests more than one angle is in play

Not in the case of a wood chisel, some Eastern knives, etc.  In those cases there is only one angle in play, and it's the edge angle, which is equal to the bevel angle.

Edge on the other hand is ambiguous ie which edge?

If we say we're grinding edge tools, or putting an edge on a knife, there's no ambiguity about which edge.  It's edge of the knife or tool that takes care of the business at hand.

And what is an edge?  It's an intersection of two planes.

And what is an edge angle?  It's the angle at which those two planes intersect.

[Elden]

All you lawyers, get your terminology straightened out!
Actually I agree with Herman. Because we are dealing with Tormek equipment, I don't feel we need to muddy the drinking water by excavating a new path through their operators manual that comes with the machine.

[Herman Trivilino]

All you lawyers, get your terminology straightened out!

Lawyers may have a reputation for arguing over terminology, Elden, but I'm in academia and I think we're even worse about that sort of thing.  It's just that when we do it there's far less at stake. 

[Rob]

So personal preference would be included but you've obviously been careful in choosing your terms given you've referenced Tormek so you're equally correct. Thus its important we now understand these terms are synonyms and interchangeable.

So at the risk of repeating myself....we have synonyms that describe the same scenario. This isn't about right and wrong, the goal here is to unite our understanding about terms so we all share the understanding of common terminology. You might like edge, I might like included, someone else might like " the tapering metallic molecular structure reaching its apex". The point is by discussing common terms we share understanding and move forward

If ever there was area for angular confusion it's knife bevels.

Your post brilliantly illustrates my original point.

[Rob]

That's interesting. This is precisely my point....the terminology is confusing. So for you...edge angle and included are synonyms but all sources agree on bevel.

Yes, but this is the Tormek forum.  Newbies coming here, and experienced users too for that matter, are looking for information that clarifies and goes beyond what's found in the Tormek manual and other Tormek literature.  To my mind it'd be better if we use the same terminology as Tormek uses. 

You see to my mind edge is more confusing than included because included suggests more than one angle is in play

Not in the case of a wood chisel, some Eastern knives, etc.  In those cases there is only one angle in play, and it's the edge angle, which is equal to the bevel angle.

Edge on the other hand is ambiguous ie which edge?

And what is an edge?  It's an intersection of two planes.

And what is an edge angle?  It's the angle at which those two planes intersect.

Again....thank you for reinforcing my original point Herman about the ambiguity of the terms, in this case edge angle.  Which intersecting two planes do we refer to?  Is it the plane between the top side and bevel one, is it the apex of the two bevels or is it the intersection of the second bevel and the under side of the knife?  Each is by your own definition an "edge" ie the intersection of two planes.

The point is not to split hairs but to genuinely highlight how downright confusing this terminology is (and why my personal preference leans to Leonard Lee and his included angle which through basic linguistic meaning must refer to more than one angle).  Whilst you're correct about the Tormek adoption of edge angle, as I've just demonstrated, academically it could legitimately refer to three different intersecting planes in one double bevelled knife.  If that's not confusing then I don't know what is.

So, knowing all this, every time I read data about knife sharpening angles, I'm always trying to establish if they refer to the bevel only or both bevels. Armed with all possible synonyms my arsenal of understanding is complete and I can stampede towards my chosen sharpening method without fear of contradiction, as can someone new to this world.

They can read the manual, find the term edge angle and if that suits, great, on they go.  Or...they might find one of Kens many recommendations for Lees book, just as I did.  They may come to the table armed with perspective from a myriad different backgrounds. Wouldn't it be nice if after one post they had all confusion expunged for all time having encountered all common and likely alternatives.
The collection and uniting of those confusing basket of terms is the goal here. It's not binary, not black, not white, not right, not wrong. It's about understanding to facilitate efficient action to yield the desired result. I'm losing the will to live now!

[Herman Trivilino]

Which intersecting two planes do we refer to?

The two that intersect to form the cutting edge.

[casher50]

I am experimenting with putting a toothy microbevel (edge) on a bevel polished up on a SJ (4000) wheel. This should be the best of both worlds: a beautiful bevel with an edge that cuts tomato skins cleanly.

Do this by:
Step1: Polish the bevel to a high shine with a 4000 grit Japanese Water Wheel.
Step 2: Establish a microbevel: Make the edge toothy by sharpening just the edge of the polished bevel with a coarse stone like the original 220 grit Tormek wheel. This will likely require using the marker method and making one or two light passes on each side. Most likely little or no be burring will be needed.
Step 3: Test results.
Step 4: Repeat and refine as needed.