22.5 deg????

B

Byrdmando

Joined
Nov 26, 2014
Messages
26
My three sided sharpening stone came with a 22.5 degree angle guide. I used this for many years because I did not know any better (and has since been lost)....But my question is, Would this not make a 45 degree "All inclusive" knife edge? If that is the case, that seems more appropriate for a chisel or maul but not a real sharp kitchen knife or hunting knife.

Where did the 22.5 deg "rule" come from and this mostly just ignored? I was thinking I wanted my knives more of the 20 -30 deg. variety.

Any thoughts?

Byrdmando
Coleman Falls, Va.
 
Yep, 22.5 dps makes for a 45º inclusive bevel. Chisels are much thinner than that. Even axes are more acute. That setting was probably chosen to make a micro bevel easier to apply which means that an uninformed person would think that he was getting good results fast. Thing is, that if you continue with micro beveling at that angle, then is that it will eventually rebevel your knife at that angle which is way too thick for efficient cutting.
 
Your on the right path.

Where did it come from? Someone that didn't understand geometry.

If you stay between 15-20 dps your good, just try to not go over 20 dps.
 
Jason B. said:
Your on the right path.

Where did it come from? Someone that didn't understand geometry.

If you stay between 15-20 dps your good, just try to not go over 20 dps.
Click to expand...

Thanks Jason. I have spent hours on your sharpening threads and really appreciate you putting all that together. I have learned much but also learned how much I dont know.

That said...What is DPS?
 
A lot of quick & basic sharpening 'tutorials' on the web, or maybe even within the published instructions for a given knife or sharpening tool, will often start with a demonstration of how to 'set' the angle with some repeatability. To do this, they'll start by placing the knife blade perpendicular to the surface of the stone (@ 90°; edge down & spine up), then turn the blade to 'half' of that (45°), then turn again to half of that (22.5°). I'm convinced this is where that 'odd' number got started, as a thumbrule for setting (or better described as 'eyeballing') the angle. It's a starting point to make the beginner's process easier in creating a new 'edge', but not even close to optimal for most uses.

As mentioned, you're better off staying somewhere at/below 40° inclusive (20° per side) or lower, and many of us around here would still prefer to go somewhere near the 30° inclusive mark, or even lower. At that level, you'll really see cutting performance change for the better, as compared to using the same blade at 40° inclusive or wider.


David
 
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yea in culinary school we were taught the half of half thing for use of a steel
you start with the edge perpendicular to your steel (90deg) then you angle it to half that (45deg) and half of that (22.5deg)

its obviously not ideal but on a basic steel, not one of the diamond coated sharpener ones. a steel is just to re align the edge not to actually sharpen the knife so even if your knife was sharpened to a 20 or less deg per side there isnt any issues with using your steel at a more obtuse angle since all your doing is pushing the edge back to the middle so its properly aligned. If you use a steel at too acute of an angle your just wasting time since the apex of the edge wont make contact with the steel. I think thats why they taught us 22.5 as it works for all the different brands as long as they have an edge of 22.5 or less and because its an easy angle to learn. later on they did teach us how to properly use a stone and most students were taught how to do it at 15deg per side, except for a couple students that had Japanese knives that only had a single edge

i cant remember the brand but i sharpened a few knives for my friends in class that had a factory edge of 22.5 on a chef knife! thats a pretty common factory edge on pocket knives but i had never seen a chef knife at such an obtuse angle. I was also very shocked to find out benchmade does a 30 deg per side or 60 deg inclusive as their factory edge on most of their pocket knives. I had to double and triple check that when customer service told me that, i thought for sure they meant a 30 degree inclusive (15 per side) but they do in fact use a 30 degree per side!
 
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