How much do sharpening angles matter?

J

J1427

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Sep 2, 2013
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Hey guys, so I've been wondering how big a difference there is between a 30 degree edge and a 40 degree edge (inclusive of course). And don't say about 10 degrees haha. Is there a very noticeable ease of cutting with the 30? Is it noticeably weaker? I'm talking for light EDC, but also for harder use. Will the 30 cut through cardboard easier? Will it chip/roll easier if used for woodwork? How would 14C28N hold up with a 30 degree angle? Sorry for all the questions, you guys are who I come to for answers though! Thanks in advance guys.
 
Allot depends on how well it was heat treated. I would try a 30 degree bevel with a 40 degree micro bevel for that add strength to the edge.
 
It's does make a noticeable difference in ease of cutting at normal production knife thickness behind the edge..... .025" +

However if the behind the edge thickness is very thin, say in the .015" range or less it's less noticeable.
 
It would be in the skyline. Not quite sure what the thickness behind the edge is.
 
I use DMT diamond stones and sharpen at around 20-25 degrees for most of my knives.

I don't really concern myself with bevels and micro-bevels, just sharpen at what I feel is a good/fairly acute angle. Seems to work really well.

My question (if I may piggyback here for a moment J1427)... SHOULD I be more concerned about these bevels and other things?
 
Without seeing the blade, or knowing what your intended use is, I wouldn't feel comfortable taking 14C28N down to 15 dps. That's getting pretty thin, IMHO. I typically run my Millies at a 17 dps, and my heavier use knives at a 20 dps. It takes a pretty tough, hard use steel to support that angle. I use it on steels like: CTS-204P, M390, M-4, S90V, etc. I know from experience that those steels will stand up to those thinner edges. I also know that I only slice/cut with my Millies. I use them for "knives". :) I run my Strider SMF in CPM-154 at 20 dps. That is a great steel, but that's a bit more of a hard use knife. I would be more tempted to "push it" a bit harder in use than my Millies. Same for my Hinderer Spanto in Duratech 20CV.

I guess what I'm saying is match the edge to the steel and the use.

And yes, there can be a huge difference in 15 dps (30 inclusive), and 20 dps (40 inclusive). The difference can be amazing with the right steel, disastrous with the wrong. I would personally go with the 40 inclusive on that steel. Ultimately I would start there. You can go down if you want later.
 
Edge geometry dictates what the possibilities are; steel type and heat treat is second. Or, you can't put a straight razor edge on a meat cleaver and have a good outcome.
 
Angle matters enough that 420HC can out cut BG 42 if it has a thinner edge.
 
J1427 said:
Hey guys, so I've been wondering how big a difference there is between a 30 degree edge and a 40 degree edge (inclusive of course). And don't say about 10 degrees haha. Is there a very noticeable ease of cutting with the 30? Is it noticeably weaker? I'm talking for light EDC, but also for harder use. Will the 30 cut through cardboard easier? Will it chip/roll easier if used for woodwork? How would 14C28N hold up with a 30 degree angle? Sorry for all the questions, you guys are who I come to for answers though! Thanks in advance guys.
Click to expand...

Most any decent cutlery steel will hold up just fine at normal cutting/slicing chores, with a 30° inclusive angle; oftentimes, even lower. The benefits gained by the thinner geometry will far outweigh any small gains in edge durability at a thicker angle.

I've looked at it like this: there's not much incentive to protect the geometry of a 40° inclusive edge, when it won't cut nearly as efficiently after the crisp apex is gone (and that usually happens pretty fast). A 30° inclusive edge, or thinner, will continue to cut reasonably well in the vast majority of 'normal' knife tasks, after the hair-splitting/shaving apex is gone, whereas a 40° edge will become obviously 'blunt' and nearly useless. The geometry behind the apex makes the bigger difference, because a crisp apex is almost always a fleeting thing, regardless of which steel is used.

For some real-world perspective, Buck Knives changed the edge grinds on all their knives a few years ago, to 26-32° inclusive; most of their standard line is 420HC. They did this, because after extensive testing, they realized the gains in cutting efficiency actually made their useful edges last longer. Previously 'thicker' edge grinds maintained their geometry well, but never performed (cut) as well in the first place.

I never really knew what 'sharp' meant in a knife edge, until I started regularly producing crisply-apexed edges at 30° or lower. There's a big and very noticeable jump there, in cutting ease and efficiency, as compared to thicker edges. I've since done all my edges this way, regardless of steel, and have never regretted it.


David
 
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J1427 said:
Hey guys, so I've been wondering how big a difference there is between a 30 degree edge and a 40 degree edge (inclusive of course). And don't say about 10 degrees haha. Is there a very noticeable ease of cutting with the 30? Is it noticeably weaker? I'm talking for light EDC, but also for harder use. Will the 30 cut through cardboard easier? Will it chip/roll easier if used for woodwork? How would 14C28N hold up with a 30 degree angle? Sorry for all the questions, you guys are who I come to for answers though! Thanks in advance guys.
Click to expand...

I have a Kershaw Barrage in that steel and have gone as low as 25-26 inclusive, it should handle 30 no problem.
 
On most stuff I'll reprofile to 30 degrees then use it for awhile and see how it holds. When it needs resharpening, I'll usually go with a 40 degree micro for how quick it is to sharpen and maybe to save a little metal, and this 30-40 combo seems to work well on just about everything in my use. Some steels however, it seems it's almost a disservice to them to have them more obtuse than 30 degrees.
 
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