MEMBER ITEMS FOR SALE
Custom Knives | Other Knives | General Items
-------------------------------------------
New Posts | New PhotosAll Photos



Go Back   The Knife Network Forums : Knife Making Discussions > Custom Knife Discussion Boards > Knife Making Discussions > The Newbies Arena

The Newbies Arena Are you new to knife making? Here is all the help you will need.

Reply
 
Thread Tools Display Modes
  #1  
Old 12-13-2016, 01:58 PM
Johnnyjump Johnnyjump is offline
Member
 
Join Date: Nov 2010
Posts: 27
Blade Geometry Question

I have to admit, I am confused on how to calculate primary and secondary bevel angles. Using angle blocks or angle gauge, I have in the past determined the primary grind angle at say, 4 degrees. Other sources describe the angle as much larger. For example, one article describes the idea of "doubling" angles: "The complete cutting angle of the knife (which is rarely referred to and is composed of the sum of both edge angles) is called the included angle. Since most knife blades are ground symmetrically, in most cases, the included angle for a knife is simply twice the edge angle." http://kitchenknifeguru.com/knives/knife-edges-101/

I think I understand the doubling aspect of the knife edge angle; but are we talking about the primary or secondary bevel? In my 4 degree illustration above, is the primary complete cutting angle 8 degrees? If I grind the secondary bevel at 15 degrees would the complete cutting angle be 30 degrees?

Still confused.
Reply With Quote
  #2  
Old 12-13-2016, 04:54 PM
Ray Rogers's Avatar
Ray Rogers Ray Rogers is offline
Founding Member / Moderator
 
Join Date: Jun 2002
Location: Wauconda, WA
Posts: 9,840
I've been making knives for 20 years and with the exception of about the first 15 minutes as a newbie trying to understand exactly the same thing you are puzzling over I have never needed to calculate an angle. I'm pretty sure the vast majority of makers who have been making knives for a while long ago gave up any such thoughts because it simply is not necessary.

You take your profiled blade and scribe a line down the center (or two lines slightly apart if you like that way better). Then you grind the blade by hand from the edge to the spine, working each side alternately, until you have the primary grind completed. That's all there is to it, who cares what that angle might be? It will be different for every thickness of blade stock and every different width of your blades.

For the secondary - which only gets done after the HT and all finishing work is completed - I like to set my platen to the angle I want, say 10 degrees. Then I can hold the blade perpendicular to the floor and just stroke the belt working side to side until the edge is sharp. Then I go to my Edge Pro (a large Lansky) which I set to the same angle and finish the edge. That gives me a 20 degree included angle which is good for most general purpose work. There are many other ways to do the same thing and other guys will likely throw some out here for you but they are all more or less the same.

Finally, you might use 8 degrees included angle on a sushi knife or some such but for most knives that would be too thin. The secondary angle is chosen based on the work you expect to do with the knife but probably the majority end up around 20 degrees ...


__________________

Your question may already have been answered - try the Search button first!






Reply With Quote
  #3  
Old 12-14-2016, 08:20 AM
ricky_arthur's Avatar
ricky_arthur ricky_arthur is offline
Skilled
 
Join Date: Dec 2012
Location: Utah
Posts: 524
Ray said exactly what I was thinking. Don't over think it. Just make knives till you figure out what works.
Reply With Quote
  #4  
Old 12-14-2016, 10:59 AM
Wrankin Wrankin is offline
Enthusiast
 
Join Date: Dec 2013
Location: Durham, NC
Posts: 42
I would look for a better, or at least clearer, source of information than that page you cited. For example:
Quote:
BEVEL: The term bevel is commonly used for any surface on the blade that has been ground to form the edge. The primary bevel is the largest (and most visible) and can vary greatly in depth?from a 32nd of an inch to 3/8ths or larger. Go to the kitchen and look closely at the blade of your chef knife. You?ll notice near the edge of the blade there?s an area where it angles more steeply?that?s the primary bevel.
That's an incredibly confusing statement no matter how you read it.

Some of the confusion stems from the fact the Japanese terminology (which is often used in the context of kitchen knives) reverses the two terms. What they refer to as the "primary bevel" would be better translated as "primary edge bevel" and is what we think of as our secondary bevel. Their secondary bevel is our primary.

The "compound bevel" examples on that site we would refer to as a secondary bevel plus a micro-bevel.

The figures on the size are misleading because they are only showing the geometry for the very edge (maybe the last 1/8 inch) rather than the cross section of the full blade.

-b


__________________
-bill rankin
Reply With Quote
  #5  
Old 12-14-2016, 01:58 PM
Johnnyjump Johnnyjump is offline
Member
 
Join Date: Nov 2010
Posts: 27
Hey, I appreciate your suggestions! Especially with years of experience behind it.
Reply With Quote
  #6  
Old 12-14-2016, 04:07 PM
jimmontg jimmontg is offline
Guru
 
Join Date: Jan 2016
Location: Now live in Las Cruces NM.
Posts: 1,345
As said above material and use makes a difference

I am going to make some filet knives out of 3/32 CPM S30V and will put a compound bevel on the edge. I will make the edge a little steeper than the rest of the 10 degree edge as it will have to cut through bones and a 15-20 degree or so edge is what I'll use. For a skinning knife I wouldn't go so steep. Now I read, but have never used it, but CPM 3V can take a much thinner edge without chipping as it is very tough, but at only 7.5% chrome it isn't stainless and many fishermen don't want a non stainless filet knife even though 7.5% would definitely be noticeably more resistant to rusting and won't rust if cared for.

I have angle blocks and precision protractor (worked in metal trades), but I never use them except to set my grinding table to the platen. I finish sharpen by hand anyway and use no guides at all. Mostly I use an almost 20 year old EZE Lap medium diamond on a wood block for most things and that's where I stop as it has worn down to a medium fine and that's good enough for most applications, certainly don't need hair popping sharp for a filet knife as it cuts through the skin when trying to take the skin off. Same for a kitchen knife, just needs a working edge not a leather cutting edge or for wood carving.

Last edited by jimmontg; 12-14-2016 at 04:09 PM.
Reply With Quote
Reply

Tags
angle, bee, belt, bevel, blade, blades, degrees, edge, fishing knife, grind, hand, how to, japanese, knife, knives, make, makers, making, newbie, sharp, thickness, throw


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
A question on blade geometry Doug Lester Ed Caffrey's Workshop 2 05-24-2010 11:39 AM
Question on edge geometry DiamondG Knives Ed Caffrey's Workshop 6 09-09-2008 07:52 PM
Blade geometry & steel recommendations for an EDC folder blade? mark23 The Folding Knife (& Switchblade) Forum 7 07-15-2004 06:33 AM
Blade Geometry Bernie Pavlik Knife Making Discussions 2 04-17-2003 06:13 PM


All times are GMT -5. The time now is 11:09 AM.




KNIFENETWORK.COM
Copyright © 2000
? CKK Industries, Inc. ? All Rights Reserved
Powered by ...

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
The Knife Network : All Rights Reserved