Sharpending Angle for Various RCs

[pastormarty]

Does anybody have a guideline for 40deg vs 30deg vs even sharper given different RC values? I know that something like ZDP189 at 64+ can be taken very acute. I know my cheap Gerber paraframe cannot. I am still trying to figure it out on my Moras, Kabars, VG10 Sydercos and Beckers.

 

[Robs92XJ]

I would say it depends on more than hardness. It will also depend on toughness and intended use, and what you will accept in terms of edge damage if it is occasionally used rougher than you intended. For example, chopping with two different steels at the same hardness and same edge geometry, the tougher one may roll if you hit a rock, the more brittle one may chip. You might tolerate the rolling but not the chipping, so the brittle steel will have to get a more obtuse edge when resharpened. Also, some steels with very large carbides will not tolerate an extremely acute edge.

However, I think most steels can handle a 30 degree edge and many can go finer, for most things you would want to do. It seems to me knife manufacturers overbuild their knives to limit warranty claims and negative reviews from the lowest common denominator of knife users. That's sensible, but there is a lot of performance you can unlock if you remove a bit of steel at the edge. Try taking one down to 25 inclusive and see what happens. If you find it's too fragile, but a 30 degree micro bevel on it. If that's too fragile, but a 35 degree micrco bevel on it, and so on.

I doubt there is anything like a published guideline for this, because there are a lot of variables and several of them are determined by the user. Some people want an edge that is nearly impossible to damage, some want the highest performance possible and don't mind if they have to treat it like it was made of glass.

 

[Belker]

Robs92xj, from what little I know, that seems like a very good explaination to me.

 

[diff_lock2]

30 inclusive without a micro bevel is pretty weak. spydercos VG10 with a true single bevel V edge at 15deg per side is only strong enough for light duty tasks and soft materials. Just a few more degrees per side will add tremendous amounts of durability. micro bevel is almost necessary.

 

[Robs92XJ]

30 inclusive without a micro bevel is pretty weak. spydercos VG10 with a true single bevel V edge at 15deg per side is only strong enough for light duty tasks and soft materials. Just a few more degrees per side will add tremendous amounts of durability. micro bevel is almost necessary.

This is kind of what I am talking about. I have a different opinion on this. My Paramilitary 2 in S30V holds up fine to heavy wood cutting (by heavy I man cutting seasoned hardwoods and not being particularly careful about cutting through knots) and other utility tasks I have put to it so far. Its only notable ding is from tapping a ceramic coffee mug while sitting on my desk. It is sharpened freehand at the factory angle which is about 30 degrees. It should have similar edge geometry to the VG10 Spyderco.

This could be a difference between S30V vs. VG10. I doubt the S30V is any harder than the VG10 (I imagine both are about HRC 60), but it might be tougher. It could also be a differing usage. The hardwood is about the hardest thing I cut with that knife. IMO its pretty rough on an edge, especially cutting across the grain or into knots. But I haven't had to cut electrical wires or heavy rope or anything like that.

My first real knives were moras and other scandi blades. These have edge angles of 20 to 25 inclusive. They are definitely more fragile than most edges, but if you use them correctly they hold up. I came to favor the lower edges angles despite having to take more care, and having to sharpen more frequently. That is what influences my opinions now, so that when I get a new Benchmade with a 40 degree inclusive angle it doesn't seem to work right until I lay the bevel back a bit.

I guess my point is, you have to experiment and see. Knowing the steel type and rockwell hardness alone will not be enough. I like the approach of starting out very acute and then micro-beveling at more obtuse angles until the durability is acceptable.

 

[Lagrangian]

I like this post by Cliff Stamp about Rockwell C Hardness:

"Steels which are one HRC apart can have very different properties, but it is not because of the hardness itself. The hardness itself is linear with strength, so moving from 58 to 59 HRC would give an increase in strength of about 2%. There is no way that itself would make a significant effect, CATRA machines have a one to one variation an order above that.

When heat treatments are modified to improve steels microstructure of the steel they can increase the hardness as a side effect. But again it isn't the fact that the steel is harder that made the significant difference. The microstructure also can cause a steel which is softer to be more brittle or a steel which is harder to be weaker."--Cliff Stamp
https://www.spyderco.com/forums/sho...d-CrimsonTideShooter-test&p=732127#post732127