Edge geometry?

MikeC

MikeC

Joined
Sep 16, 2005
Messages
1,364
Okay, can someone please clear this up, I think I have it but am not sure.

Edge geometry is the angle at which the edge is sharpened on the blade, correct? If this is the case if I use a sharpening system at 25 degrees per side I have a finsihed edge which is 50 degrees? Is this right. If so I have read that most knives come from the factory at 30+/- degrees, so this means 15 degrees per side, right, or am I reading this wrong and there just quoting the angle used on one side and not the total angle, which would at 30 degrees per side be a total of 60 degrees. I have seen so many youtube vids, and read so many post where people use the terms intermidently I can't tell who or what is right? Can someone please straighten this out. I have tried using my system at 15 degrees which is the lowest angle provided and it is just too much and the edge is just too thin, but 15 on both sides equals t30 degrees which by definition is for heavy use. So something is wrong here. I think people such as myself aren't clear on what the right measure of angle is, because too many people use the terms incorrectly. When people say a 30 degree angle is for heavy use they mean 30 degrees per side which is actualy a 60 degree edge, is this right? HELP??
 
Generally the edge angle for a knife is from 50 to 30 degrees total. So divided that by two to get per side angle. Most hard use knives are 40-50 degrees total for the edge stability as you found out when you tried the 30 deg edge. 30 deg is more for soft materials and is more suited for tougher steels.

If you find that 30deg is too thin for your use go to 40deg. If even that is not working out go to 50deg. If even that goes bust, you need to find a new knife with better steels for the blade or you need to get a crowbar. ;)
 
kevtan said:
Generally the edge angle for a knife is from 50 to 30 degrees total. So divided that by two to get per side angle. Most hard use knives are 40-50 degrees total for the edge stability as you found out when you tried the 30 deg edge. 30 deg is more for soft materials and is more suited for tougher steels.

If you find that 30deg is too thin for your use go to 40deg. If even that is not working out go to 50deg. If even that goes bust, you need to find a new knife with better steels for the blade or you need to get a crowbar. ;)
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I would disagree with that. Thinner angles are for Harder steels, not Tougher steels.

The thinner the blade, the stronger the alloy must be to prevent rolling of the edge. That requires a harder steel, not a tougher steel.

Normally, if I were talking to folks about edge angles, I would say "30° inclusive" if I am talking about both edges together. I would say "15° per side" for a single side. That way wrong assumptions are not made.
 
knarfeng said:
I would disagree with that. Thinner angles are for Harder steels, not Tougher steels.

The thinner the blade, the stronger the alloy must be to prevent rolling of the edge. That requires a harder steel, not a tougher steel.

Normally, if I were talking to folks about edge angles, I would say "30° inclusive" if I am talking about both edges together. I would say "15° per side" for a single side. That way wrong assumptions are not made.
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I have had good results from plain old mild steel grinded and sharpened to 15deg per side cutting something with the consistancy of cheddar cheese. Never seems to need sharpening or steeling unless the edge hit something harder than a the cutting board. I have also had a ceramic blade sharpened to 40deg total that chips like crazy when whittling wood. Never happens to my M2 convexed blade from a hacksaw blade. So take your pick on what works for you.
 
knarfeng said:
I would disagree with that. Thinner angles are for Harder steels, not Tougher steels.

The thinner the blade, the stronger the alloy must be to prevent rolling of the edge. That requires a harder steel, not a tougher steel.

Normally, if I were talking to folks about edge angles, I would say "30° inclusive" if I am talking about both edges together. I would say "15° per side" for a single side. That way wrong assumptions are not made.
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Yep, that is why all those TV-chefs with german knives (Henkels, Zwillings etc) continously steel their blades. They have a hardness range of 55-56 which means that they roll very easily and requires constant steeling.

High hardness prevents rolling. Small carbides prevent tear-outs and chipping.
 
What does steeling mean? I have Henckels and they seem to get dull easily especially the steak knives.
 
ratdog said:
What does steeling mean? I have Henckels and they seem to get dull easily especially the steak knives.
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Cutting on a plate probably has a lot to do with that. Glass is harder than steel on Mohs Scale of Hardness

Hardness Substance or Mineral
1 Talc, graphite
2.5 to 3 Pure gold, silver, aluminium
3 Calcite, copper
4 Fluorite
4 to 4.5 Platinum
4 to 5 Steel
5 Apatite
6 Orthoclase
6 Titanium
6.5 Iron pyrite
6 to 7 Glass, fused quartz
7 Quartz
7 to 7.5 Garnet
7 to 8 Hardened steel
7.5 Tungsten
8 Topaz
8.5 Chrysoberyl, chromium
8.5 to 9 Tungsten carbide
9 Corundum
9 to 9.5 Carborundum
<10 Ultra-hard fullerite
10 Diamond
>10 Aggregated diamond nanorods, Rhenium diboride
 
ratdog said:
What does steeling mean? I have Henckels and they seem to get dull easily especially the steak knives.
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Steeling means making sharpening motions of the knife against a smooth steel rod. It does not sharpen the blade. Sharpening means you are removing steel from the blade. Steeling a blade straightens the edge and does not remove steel from the blade.

When you are cutting with a soft steel, you sometimes cut with so much force the the thin edge of the blade bends over and is no longer straight. When you steel, you force the blade edge back to a flat straight edge.
 
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