Proper sharpening angle

[schoolmaster]

What is the best angle to properly sharpen a knife for edge retention and sharpness?

[Ranger99]

never checked it.
i do all mine freehand with a stone.
i would imagine it would vary with
the way it was edged when made
and material and hardening would
factor also.

[Bugflipper]

Depends on the steel and what you cut. I like about a 25 degree angle on a good knife . It seems I read something a long time ago as 5 quarters stacked was the right angle for a pocket knife. Seems like 4 was for a light use knife like a small game knife. Assuming that translates to about 25 and 22 degrees. I have one in the toolbox that's probably about 30 degrees though. Inevitably I will have to abuse that one every now and then.

[FPH]

I try for 22 degrees.

[Joel]

I really don't bother with numbers, I just grind the blade to as thin an edge as possible; given the steel hardness and  thickness.  One thing to keep in mind when people discuss sharpening angles is the the actual angle is not 20 or 22 or 25 etc degrees; that is the angle of one bevel.  The INCLUSIVE angle( the sum of both bevels) would actually be 40 or 44 or 50 degrees.  It sort of gives a different picture, to me anyway.  I'd read years ago that the actual "cutting edge" of a knife is only 1 to 3 microns thick..the area directly behind that is more correctly called the "shoulder".  It stands to reason the flatter the shoulder angle(more degrees) the more force is required to shove that tiny cutting edge through a material....not that it involves King Kong or something. The less force placed on the bitty edge, the longer it lasts and the easier it moves through the material; which is why thin edges cut so well.  At the same time that shoulder does help support the tiny cutting edge from rolling to one side of the other, so steel hardness is a definite factor in choosing an angle.  In some cases a thick bevel is good, especially when the knife is not used for cutting directly into a material, i.e. knives used in woodworking/carving/shaping can benefit from a thick bevel since it's being slid at a very shallow angle along the material, rather than into it.....it gives better control.  My own knives are all thin bladed and when I sharpen them I hold them often only a few degrees from the vertical on the belt so I'm thinning an already thin material...but then again I use steel with a hardness of around 60-62 Rockwell C.....I'm probably using an inclusive angle of around 25-30 degrees( 10-15 degree single bevel).  Even my machetes are ground thin.  It's different with my axes, even though I do thin the material.   I also grind with a convex edge so it's a different geometry.  On softer, thicker steels you may need a bit more shoulder to keep that "cutting edge" from rolling quickly on you, so you can go with a 40 or 44 degree inclusive...it may not be as "sharp" as a thinner edge, but it will last a bit longer....and so on.

[jamaldog87]

my stone came with a 25 degrees angle guide on it and all my swords and machete  i used a 30-35degrees angle. i was always told for fine cutting like meat or grass a 25 was best and for heavy cutting like wood   a 30 to 35 was best.

[gcrank1]

I cant count the number of times Ive run some blade across the stone at an angle I thought would be good and after a few strokes and inspection found I was stoning up on that 'shoulder' Joel so aptly described. So, yes, I fully agree it will depend upon what kind of grind you are starting with, a convex with a beefy shoulder will not take as fine an angle as a flat ground blade. I know there are some illustrations of grinds 'tip on' to see how this translates to what kind of angles you might intend.
Ive thinned a few blades by hand to get that shoulder down so I could use a finer angle and have been pleased with the results. Too much beef makes a knife more like an axe edge and I want a knife to be more of a slicer. If I have my druthers I'd rather have a flat grind or a very thin convex, too many convex are too fat for me.

[mechanic]

It's all about usage for me.  I carry a cheap pocket knife for work to cut hoses, wiring or whatever.  I take a coarse carborundum stone to it at a steep angle so  the edge does not roll or break easily.
 
The knife I carry hunting is closer to a straight razor, hollow ground and sharpened at almost no "angle".  I don't cut bone with it, only flesh, and certainly I don't use it like the guy on the survival show and force it through wood to split it.
Ben