April 30, 2014 at 1:01 pm #11879
Article by Author: Joe Talmadge
Welcome to the blade geometry FAQ. Our objective is to provide a working knowledge of blade shapes and grinds. After reading the FAQ, I hope you’ll be better able to answer the question, “I need to do job X, what kinds of knives should I consider?”. We will start with some general characteristics of blade shapes, then talk about blade grinds, then put it all together to discuss specific blade patterns. The last section, a brief analysis of some common designs, will build upon the previous sections. It’s important to keep in mind that the characteristics can be as important as blade shape. When you’re done with the FAQ, you should be able to make decisions not only on blade shape but on other attributes. If you need to slice, you’ll know to look for a nice curving belly — and not get hung up on what the ostensible blade shape is supposed to be.April 30, 2014 at 2:18 pm #11885
How blade sharpening angle effects cutting abilities:
From the sharpening supplies web site: http://www.sharpeningsupplies.com/?gclid=CPmTk5uziL4CFaVxOgodwmUAKw
“Under 10 Degree Angles
The lowest angles are reserved for edges that are typically cutting softer materials. In this case, the edges are not subject to abuse so the lower angle can be maintained without damage or edge failure. The lowest angles that we typically see are on straight edge razors. These are sharpened to an angle which is roughly 7 to 8 degrees (although the back of the blade is used as a guide so knowing the angle isn’t important and nor is it adjustable). A straight razor has a very delicate edge that is very easy to damage. In proper usage, a straight razor would never see the type of use that would damage the edge.
10 to 17 Degrees Angles
A sharpening angle of 10 to 17 degrees is still quite low for most knives. With a total angle of 20 to 34 degrees, this is still a very fine edge. This edge is typically too weak for any knife that might be used in any type of chopping motion. Also consider that harder steels are also more susceptible to impact damage because they are more brittle. If your knife is used for cutting soft items or slicing meats, this lower angle can hold up and provide a very smooth cutting action.
17 to 22 Degree Angles
A 17 to 20 degree angle covers most kitchen knives. Some knives (typically Japanese manufacturers) will sharpen their knives to roughly 17 degrees. Most western knives are roughly 20 degrees. It is our experience that kitchen knives sharpened to 15 to 20 degrees cut very well and are still durable. These angles are still not highly durable as a total angle under 40 degrees will not respond well to rougher treatment in harder materials.
22 to 30 Degree Angles
In this range, the knife edges are considerably more durable. A pocket knife or a hunting knife will inevitably see abuse not seen by knives meant primarily for slicing or chopping softer materials. While the edge may not ultimately be cut as well (but you may not notice a difference) it will be considerably more durable.
Over 30 Degrees Angles
Any edged tool or knife that is sharpened past 30 degrees will be very durable. Its cutting ability will be noticeably reduced. This durability has an advantage because more force can be used to make the cut. While the majority of knives won’t benefit from this sharpening angle, an edged tool like a machete, cleaver or axe must be durable as the typical cutting action of these tools would damage other edges”
It’s interesting how such simple tools can have the effectiveness altered by a change of only a few degrees of angle in the shape of the edge.April 30, 2014 at 5:04 pm #11928
Interesting & useful topic. Thanks 1974.April 30, 2014 at 5:06 pm #11929
74 thanks for the article. I had never looked into why different grinds were used, I just knew what they were. This will definitely be useful building knives in the future.April 30, 2014 at 6:03 pm #11936
If you get into forging knives you might want this video. http://usaknifemaker.com/dvd-rob-hudson-blade-forging-to-shape.html
I lived near Rob and had a chance to be in his shop just after he passed the guild test for Master Smith. If you look up his name you will find his knives and swords that were made at the highest level of craftsmanship.
(Not to be confused with Robscustom knives in Pa.)
Attachments:You must be logged in to view attached files.
You must be logged in to reply to this topic.