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back bevel
- Thread starter EdLin
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Resharpening is a heck of a lot easier.
Also, you can make a back-bevel of any degree. You can make a five degree back bevel if you have the right steel and that will make a 15 or 20 degree edge cut much better.
Also, you can make a back-bevel of any degree. You can make a five degree back bevel if you have the right steel and that will make a 15 or 20 degree edge cut much better.
If you take a hunting knife and thin the edge out, to say, 15 deg, then putting a microbevel on it (anything over 15 deg) is much faster than if the original grind was, say, 20 or so. A lot less metal to remove. I find that it only takes a couple of strokes on a diamond hone to re-sharpen. Faster, and in my case, much easier to hit a free hand angle a couple of times, rather than 20 times or so. This makes my freehand sharpening much more accurate as well.
Cliff Stamp
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You do lose some cutting ability by applying the more obtuse bevel, in fact various people have quantified just how much is lost :
http://www.bladeforums.com/forums/showthread.php?t=305456
The advantage as Thom noted is in ease of sharpening, if 15/20 doesn't cut as well as you like then use 10/15. I run 3/6 on some of mine.
-Cliff
http://www.bladeforums.com/forums/showthread.php?t=305456
The advantage as Thom noted is in ease of sharpening, if 15/20 doesn't cut as well as you like then use 10/15. I run 3/6 on some of mine.
-Cliff
Cliff Stamp
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Yes it is freehand, getting the three part is easy, the knives are hollow ground so you just lay them on the stone, it takes no skill at all. Applying the secondary more obtuse bevel is done by raising the knife essentially the thickness of the blade, though I go more by force as you can feel the difference in pressure and I raise them up until I feel just the edge biting it for a 0.1-0.2 mm microbevel. They sharpen almost immediately as the knife is so thin, you can set calipers at 0.005" thick and it rides up into the *secondary* edge bevel. Everything machines easily when there is almost no steel to remove anyway.
-Cliff
-Cliff
I agree with Thombrogan. Since I read and learned John Juranitch's book: The Razor Edge Book Of Sharpening and learned the importance of grinding in relief and his methods of primary and secondary edges it seemed like I was sure sharpening a lot less of the time. The method turned out to be very similar to Sal Glesser's 204 Sharpmaker method. Actually it doesn't really take that much more time to do it right. The other brother is also well in line saying that you can use much more extreme angles in some of the different steels. It seems like I can get away with using a much more narrow angle with ZDP-189 than I can with VG-10 for instance. JD
And here I just thought that Canadian dimes were slimmer than American dimes... 
You want to talk about speed of steel removal, I'm posting in the shaving forum about my results in re-profiling a DOVO straight razor. Just as Cliff described, you lay the razor flat on the finest stone that you can find to hone it. I had somehow put a secondary bevel on mine by mistake (I know, I know), and had to cut down the shoulder back to where it should be. I put the razor down flat on a Spyderco fine ceramic hone, and 5 strokes per side had re-beveled the razor, knocking out the shoulder and all. That's some thiiiiiiin steel.
You want to talk about speed of steel removal, I'm posting in the shaving forum about my results in re-profiling a DOVO straight razor. Just as Cliff described, you lay the razor flat on the finest stone that you can find to hone it. I had somehow put a secondary bevel on mine by mistake (I know, I know), and had to cut down the shoulder back to where it should be. I put the razor down flat on a Spyderco fine ceramic hone, and 5 strokes per side had re-beveled the razor, knocking out the shoulder and all. That's some thiiiiiiin steel.
D_R_Sharpening
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One other thing to note....
Backbeveling will keep the thickness of the edge the same (assuming the same backbevel angle is used all the time) throughout the life of the knife.
--Dave--
Backbeveling will keep the thickness of the edge the same (assuming the same backbevel angle is used all the time) throughout the life of the knife.
--Dave--
Edlin - Great question.
When I first started learning I wondered why all knives where not "flat ground" with only one bevel. After sharpening for a few hours I realized the purpose of the primary bevel and the micro-bevel. It is lots easier and involves far less steel removal with very little degredation in cutting ability. I have discovered that some very thin knives like some kitchen knives or filet knives don't really need a primary back bevel because so little steel is involved in sharpening the edge that they are essentially "flat ground".
If you scroll down this link you will see various grinds and discussions.
http://www.jayfisher.com/Blades.htm#Knife blade relief angle and the cutting edge
When I first started learning I wondered why all knives where not "flat ground" with only one bevel. After sharpening for a few hours I realized the purpose of the primary bevel and the micro-bevel. It is lots easier and involves far less steel removal with very little degredation in cutting ability. I have discovered that some very thin knives like some kitchen knives or filet knives don't really need a primary back bevel because so little steel is involved in sharpening the edge that they are essentially "flat ground".
If you scroll down this link you will see various grinds and discussions.
http://www.jayfisher.com/Blades.htm#Knife blade relief angle and the cutting edge
tim8557 said:
You can take the EdgePro to zero by lifting the blade height on the table. Wraps of Painters Tape will do it with enough layers. Heavy plastic shims will do it as well. I took a heavy plastic back from a desk pad used a hair dryer to mold it, slips right on friction tight. Of course this will throw out the angle indicator dots but once you are done at zero ° just remove the pastic (or tape) and you are good to go.
The vast majority of blades out there do not work well with low relief grinds (back bevels) the steel and/or hardening & tempering just will NOT handle this. Even many so called high end kitchen knives are too soft for relief grinds much under 15°, they just won't last long.
I've done some experimenting with relief grinds as low as 6° and sharpening with multiple bevels. 9°, 12° 15°, 18°, 21° and 24° and various combinations there on. Back bevels starting at 6° through 15°-17° and even 20°-25°. The primary gind from 3° to 5° above that.
No true tests to confirm it but my feeling is that the more obtuse angles over the primary grind are a detriment to true "sharpness" and longevity. 3° seems to be about the best. Ie. Relief grind at 12° and primary grind at 15°. For most sharpening I am putting 17° relief grinds, polished out to 4000 grit with polish tapes then the primary grind is put on at 20° and rarely going higher than a couple of strokes with a 600 grit EdgePro stone (if that). No complaints from any customer as yet and the return customer level is high. Though for most it's only a few times per year. Average of 3.
The multi bevel route does seem to suffer past the 3rd edge. The up side is that the longevity "seems" considerably increased and touchups are a breeze. I don't think the extra work is worth the effort though.
Cliff Stamp
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QuietOned said:
Going by raw numbers, yes the vast majority of blades are really low end.
This would depend on what you are cutting and the steel, Alvin Johnson described the profile he runs on his multi-blades which all typically have the same primary edge grind but the secondary runs from just slightly more obtuse to much more for scraping blades.
In regards to the optimal micro-bevel, I don't think you can generalize to a specific increment as this implies a fixed force(depth) function and this will vary widely through various materials, it is for example much steeper for hardwood than cardboard, almost exponential decay for hemp rope and pretty much constant for working through heavy plastics.
I have a Sebenza set with a primary grind of just a few degrees, with about 15 degrees is optimal for the secondary bevel. The Sebenza can't handle a secondary bevel of 6 degrees, but the primary is fine really low assuming I am cutting soft materials like ropes, cardboard, woods, foods, etc. . I would not take it to heavy knots or work in thick plastics as it could crack the primary edge.
In regards to cheap kitchen knives, I cut all mine flat to a bench grinder which is usually 8-12 degrees depending on the blade thickness and grind. I set the edges at 20 degrees as this is where people tend to hone naturally and it is pretty easy to free hand being just half of half of 90.
I would hollow grind the edges thinner if I could on the small knives, paring and vegetable slices and meat cutters, but don't have a wet wheel. It depends on the person though, will they take that knife and try to force it through a frozen piece of minced meat.
-Cliff
After I get the desired edge by doing a Primary and Secondary edge I then take one of my Spyderco 204 Ultra Fine stones and I very gently "steel" it on that stone to remove any "micro-burrs". I have been doing a little bit of studying on "De-burring" and it is amazing how much there is to know about it. There has even been a book wrote about it.
Probably a subject that you could do an individual thread on.
Probably a subject that you could do an individual thread on.