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Flat Vs hollow ground!
- Thread starter R.Taylor
- Start date
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- Nov 13, 2004
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- 878
A druid said:I haven't figured out how and I thought the simple graphics might transfer across. Wasn't trying to take credit for the original idea anything.
Go to the article on the Internet and highlight the URL (THAT'S THE HTT:// ETC.
DO FILE "copy"
"Paste" into a reply here.
Great article and I would love to see the visuals.
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- Aug 19, 2005
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- Mar 26, 2005
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- 184
tim8557 said:
Nice article, but I don't really agree with the assessment of convex grinds. It's no way just an axe grind, as all the happy owners of, among others, Fjaellkniven knives will confirm. For some purposes it's just about the best grind there is.
Hans
The Jan 06 edition of Blade has a nice article on blade grinds. According to the article (which so happens to coincide with my own opinion) the best grind for most applications is a full flat grind with a convex edge. It combines a low profile with a strong edge. However, all that is pretty much meaningless (a Cliff would probably haste to point out) as long as you don't specify the parameters of the grinds, most importantly thickness behind the edge (were the edge grind transitions into the main blade) and edge bevel.
This edge geometry is pretty easily achieved. On any flat ground Spyderco model I like to start with a 12 deg bevel on the edge. Even though I am pretty good at holding an angle free hand I am naturally round over the edge bevel free hand anyways. Depending on the effect that I want to achieve, I raise, after polishing out the scratches of the previous stone, the angle on the finer stones (usually I progress 700, 3000, 10000) a little bit, this ensures that I work on the edge and naturally rounds the edge to a slight convex shape. I end on the finest stone at about 15 deg. The final stropping with CrO increases the angle naturally ever so slightly further.
I have reduced the thickness behind the edge on my Pacific Salt a little bit more as an experiment than a necessity, but usually I don't adjust the thickness behind the edge. I find that Spyderco does a decent job of adjusting the thickness behind the edge depending on their model and its intended task. The Lil'T for example is pretty thick behind the edge (about 0.03 in) while the Caly Jr. is about half that, which is in keeping with the indended usage of the two models I would say (the Caly Jr. is a performance slicer, the Lil'T is a brute). Adjusting the thickness behind the edge is not easy on a flat ground model (much easier on a hollow grind, a lot less material to remove) without a motorized grinder. Still possible with a good coarse stone though, but it takes a lot of elbow grease and will scratch up the blade a lot.
There is something to be said for a full convex grind or even better a median ridge geometry. I wish Ed Schempp would say something about the latter since his fixed Camp blade will feature this grind and the arguments sound very exciting. But basically a full convex grind will limit the contact of the material to be cut with the blade if the cut is deep. This reduces potential binding. The median ridge geometry has the same advantage but with the additional plus of a more balanced weight distribution between edge and spine. Obviously an argument that is irrelevant for a small slicer but important for large blades like a Katana (which all sport a median ridge geometry).
I don't really see any advantages in a hollow grind except for the ease of adjusting the thickness behind the edge, but especially for deep cuts I would say that the hollow grind is at a clear disadvantage compared to a flat grind. At shallow cuts I doubt it will make a difference.
Hope that helps. As always, just IMHO of course.
This edge geometry is pretty easily achieved. On any flat ground Spyderco model I like to start with a 12 deg bevel on the edge. Even though I am pretty good at holding an angle free hand I am naturally round over the edge bevel free hand anyways. Depending on the effect that I want to achieve, I raise, after polishing out the scratches of the previous stone, the angle on the finer stones (usually I progress 700, 3000, 10000) a little bit, this ensures that I work on the edge and naturally rounds the edge to a slight convex shape. I end on the finest stone at about 15 deg. The final stropping with CrO increases the angle naturally ever so slightly further.
I have reduced the thickness behind the edge on my Pacific Salt a little bit more as an experiment than a necessity, but usually I don't adjust the thickness behind the edge. I find that Spyderco does a decent job of adjusting the thickness behind the edge depending on their model and its intended task. The Lil'T for example is pretty thick behind the edge (about 0.03 in) while the Caly Jr. is about half that, which is in keeping with the indended usage of the two models I would say (the Caly Jr. is a performance slicer, the Lil'T is a brute). Adjusting the thickness behind the edge is not easy on a flat ground model (much easier on a hollow grind, a lot less material to remove) without a motorized grinder. Still possible with a good coarse stone though, but it takes a lot of elbow grease and will scratch up the blade a lot.
There is something to be said for a full convex grind or even better a median ridge geometry. I wish Ed Schempp would say something about the latter since his fixed Camp blade will feature this grind and the arguments sound very exciting. But basically a full convex grind will limit the contact of the material to be cut with the blade if the cut is deep. This reduces potential binding. The median ridge geometry has the same advantage but with the additional plus of a more balanced weight distribution between edge and spine. Obviously an argument that is irrelevant for a small slicer but important for large blades like a Katana (which all sport a median ridge geometry).
I don't really see any advantages in a hollow grind except for the ease of adjusting the thickness behind the edge, but especially for deep cuts I would say that the hollow grind is at a clear disadvantage compared to a flat grind. At shallow cuts I doubt it will make a difference.
Hope that helps. As always, just IMHO of course.
- Joined
- Oct 10, 2003
- Messages
- 395
One of the main differences has been mentioned is the thickness behind the edge, now go a little further back on the blade and you see in a cross section the the flat grind gets thicker the futher back you go, the hollow grind will have an area behind the blade that is parallel arcs. This will make the hollow ground knife easier to sharpen as you wear away the factory edge.
I prefer to have a varible geometry on the edge. Before the knife is sharpened after it is ground, edge thickness is not parallel. A Spyderco folder is ground to about .007 on an inch parallel. I might have .012-.015 at the plunge and the tip and .003-.005 at the belly, then I sharpen the blade with a slack belt producing an appleseed edge. This gives me several advantages. The tip is stronger and will hold the strong geometry for a long time. The plunge is where I do heavy force cuts and strip wire. The belly is extremely sharp. You can use this system on either hollow or flat ground knives. For me this system reduces sharpening frequency and adds to durablilty.
I have done all the types of grind but I do perfer the flat grind the best. Hollow grinds and convex grinds can be used to compliment the design of the knife if not functionally then artistically. Any of the grinds done properly will give good performance with the differences noted in the posts on this thread...Take Care...Ed
I prefer to have a varible geometry on the edge. Before the knife is sharpened after it is ground, edge thickness is not parallel. A Spyderco folder is ground to about .007 on an inch parallel. I might have .012-.015 at the plunge and the tip and .003-.005 at the belly, then I sharpen the blade with a slack belt producing an appleseed edge. This gives me several advantages. The tip is stronger and will hold the strong geometry for a long time. The plunge is where I do heavy force cuts and strip wire. The belly is extremely sharp. You can use this system on either hollow or flat ground knives. For me this system reduces sharpening frequency and adds to durablilty.
I have done all the types of grind but I do perfer the flat grind the best. Hollow grinds and convex grinds can be used to compliment the design of the knife if not functionally then artistically. Any of the grinds done properly will give good performance with the differences noted in the posts on this thread...Take Care...Ed