Primary bevels and microbevels

[catamount]

The primary bevels on :spyder:s from the factory vary from well below 30 degrees (inclusive) to above 40 degrees. This can sometimes be frustrating for those of us who use a Sharpmaker, and don't have the equipment, skill or patience to reprofile.

When sharpening my :spyder:s, I like to use the 30 degree rods to form a microbevel. Obviously, this is only possible when the primary bevel is less than 30 degrees. My question is this; would it be better to form the microbevel at 40 degrees, even if the blade will take one at 30 degrees? How will this affect sharpness and edge retention?

[Lostification]

Hmmmm.... I dunno. I only use the 30 degree angle. :D

[merciful]

Well, 40º inclusive is less sharp than 30º, but it'll be a little more durable. Trade-offs, trade-offs. I've got my Yojimbo sharpened to 30º with a 40º microbevel, and I can tell ya that it's pretty wicked sharp.

[dalefuller]

I've gone back and forth several times on a couple of my knives (a D4 and an H&K14210). Honestly, I can't tell the difference in the cutting I do except that when I use a 40 degree microbevel, the edge seems to last a bit longer.

I can get the edges to shave and push cut at both settings. When I use either edge in the real cutting that I do, they both work well. If I'm cutting something stiff like cardboard, the 30 degree bevel seems to glide through it a little better, but that might be because I expect it to, since the angle is more acute.

On my work knives like the D4s, I actually think I prefer a 40 degree microbevel, even on the ZDP ones. It gives me a strong, sharp edge that can go a long time before it needs more than a touchup.

[Simple Man]

I have found that for my uses, a thin 22º-25º reprofiled bevel, with a 40º microbevel finished on the 204 brown stones works best. It is sharp enough to pop hair and filet newsprint and stays that way quite well.

[Left Hand Path]

I use a 40 degree microbevel on all my knives. I do this b/c many knives are >30 degrees from the factory, and I reprofile to 30 degrees then apply a 40 degree microbevel.

Even when I am sure the knife is below 30, like on my Yang kitchen knife, I still use 40 degree micro - the microbevel is so small that I don't think performance drops, and it gives a little room for error if the primary bevel is not perfectly consistent. 40 degrees is a stronger edge with better retention, while 30 is sharper in theory but I can't tell the difference.

I think the primary bevel has a much larger effect on performance. If a knife is at 28 degrees primary, I don't think the 30 degree micro will make a big difference compared to using a 40 degree micro. However if you change the primary from 28 to 20, that will make a big difference in performance.

[LJK]

I'm always playing around with different sharping systems and different angles. So far on Spydies VG10 or S30V I like 30 primary 40 mirco the best. I'm carefull not to overdo that 40. A dozen low pressure swipes at the most seem to give me the best results. I'm only happy when its shaving sharp. Some days the same routine gets it hair popping sharp. Its a fine line between the two. One bad swipe and it goes from popping to just shaving :o

[barbes]

This is interesting. I sometimes do what you're all describing, but use a really rough stone for the microbevel -- just a few light strokes. It cuts like serrations, but doesn't hang up in fibers like serrations sometimes do. An edge like this done right will cut as well as really fancy zero grinds.

[Cliff Stamp]

I still use 40 degree micro - the microbevel is so small that I don't think performance drops, and it gives a little room for error if the primary bevel is not perfectly consistent.

Both of these are two very strong points. As some data :

http://i7.photobucket.com/albums/y269/CliffStamp/edge%20retention/lil_bear_15_20.jpg

This is a comparison of a 15 vs 20 degree microbevel, there is no significant difference in sharpness after 40 m of cardboard, but it was much easier to apply the 20 degree micro to the primary bevel for the reasons you noted.



I think the primary bevel has a much larger effect on performance.

Yes, you can estimate it by the width fraction, if the primary bevel is 1 mm wide and the micro bevel 0.1 mm then you would expect the primary grind to be 90% of the cutting ability. Generally for most knives the primary bevel is several mm so this number is usually 95% or better.

-Cliff

[Left Hand Path]

Yes, you can estimate it by the width fraction, if the primary bevel is 1 mm wide and the micro bevel 0.1 mm then you would expect the primary grind to be 90% of the cutting ability. Generally for most knives the primary bevel is several mm so this number is usually 95% or better.

-Cliff

Thanks for the data, Cliff. That confirms what I have found in my everyday use, and the quote above makes it even more clear.

[bladese97]

:spyder: :spyder: :cool: :spyder: :spyder: I like to use 30deg primary, and 40deg micro...It seems to work best on all my :spyder: s'