Grind types

A

ATaylor

Joined
Nov 23, 2013
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I've looked up and read about different grind types but don't quiet understand grind types relationship with sharpening. Do you need to sharpen each grind type differently? And if you sharpen at the wrong angle can you completely destroy or change the type of grind that was originally put on the blade? Any info will be helpful
 
The relationship with some grinds and sharpening could be concerning the thickness behind the edge. A hollow ground knife will stay thin behind the edge longer than a flat ground blade which will need to have the bevel reset (relatively) sooner.

For what it's worth I've not had to reset the bevels on any of my knives even my heaviest users.
 
If you want durable outdoor chopping edge go convex if your a whittler go with a 25 degree angle if you want to whittle hair and be dull after one cut go with 15 degree angle
 
ATaylor said:
I've looked up and read about different grind types but don't quiet understand grind types relationship with sharpening. Do you need to sharpen each grind type differently?
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Yes, you have to sharpen specific way to get specific grind. Some of them are not really achievable freehand, you'd need a system.I doubt any human can produce straight V edge w/o bionic augmentations. It will be convex...
Chisel grinds you sharpen on one side, asymmetrical edges require different angles for each side and so on...

ATaylor said:
And if you sharpen at the wrong angle can you completely destroy or change the type of grind that was originally put on the blade? Any info will be helpful
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Yes, you can change grind type, destroy the edge, knife, or even the sharpening stone...

Gregmking said:
If you want durable outdoor chopping edge go convex if your a whittler go with a 25 degree angle if you want to whittle hair and be dull after one cut go with 15 degree angle
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Angles should be more or less influenced by alloy, its properties, hardness and job type.
25 for whittling is rather vague. 25 per side? that's 50 deg total, might be necessary for very soft steel blades, but for anything at 60HRC or above, that would be tons of wasted cutting ability.
Same for 15. I have kitchen knives at 5 per side, lasts for weeks with steeling. And I do cut quite a bit of food with those.
I can't put 5 per side on mainstream 55-57hrc stainless steel knives for sure, but 64-65 HRC Aogami 1 steel handles that fine for what I use it.
I have Phil wilsons CPM 10V utility knife, 10deg per side, 64HRC. Very thin blade, works just fine for wood whittling. Keeps shaving sharp edge after hours of cardboard cutting and whittling...
 
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ATaylor said:
I've looked up and read about different grind types but don't quiet understand grind types relationship with sharpening. Do you need to sharpen each grind type differently? And if you sharpen at the wrong angle can you completely destroy or change the type of grind that was originally put on the blade? Any info will be helpful
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Would you mind clarifying your question? By "grind types" do you mean hollow (concave) vs flat vs convex? And are you referring to the primary bevel or the secondary/edge bevel?

Starting from a blank or billet, the primary grind/bevel can be "chisel" = only one face is ground down to an edge with the flat of the opposing side
- or it can be "symmetrical" = each side is ground in the same way / at the same angle to create a mid-line edge
- or it can be "asymmetrical' = each side is ground in a different way / angle to an edge.

As posted above, a bevel may be ground hollow (concave), flat, or convex at a given angle of incidence (i.e. the angle at which the hone and billet intersect). Once the primary bevel is set, usually < 5 degrees per side, a secondary edge-bevel is applied to retain strength at the apex. This secondary bevel is often < 1/16" wide depending on thickness at the edge - thinner knives may have secondary bevels only ~1/64", a "microbevel". The edge bevel can be ground any way you want - hollow, flat, convex, any angle. Less metal needs to be removed so, depending on the steel and the thickness/width of the bevel, it can be applied and adjusted relatively rapidly. Indeed, a more obtuse bevel can always be added to the apex "on top of" the edge bevel - a "tertiary" bevel. Changing the edge-bevel does NOT change the primary grind of the blade, does nothing to "destroy" the primary grind. To "completely destroy" the edge via sharpening at the "wrong angle" implies either poor technique - i.e. uneven or non-linear edge, burr, apex-rounding - or implies too low of an angle - i.e. the resulting edge is too fragile for the task and chips/folds readily. In general, with good technique, no you cannot "destroy" an edge by sharpening at an angle other than what was applied at the factory. Knife edges are customizable!! Learn/practice technique and have at it! Enjoy :)
 
Thanks for all your help. I understand now. When I was thinking of the grind type I thought it only envolved the bevel/edge of knife. I didn't realize that the grind starts at the spine and endea at the bevel. So under that assumption I couldn't under stand how you could sharpen a hollow grind type with out messing it up if the arc was located at the bevel. I understand my mistake. And understand how the grinds work and there relation with sharpening. Not an expert by no means but understand the concept. Thx again to everyone who chimed I. To set me straight.
 
I went a very very long time in my sharpening career without stopping to think about ANY of the geometry of the blade. Once I slowed down and identified the various facets (faces) of the blade that make up it's overall shape, it really helped me to understand what part of the blade I needed to grind. Of course learning how the overall geometry effects cutting took more time, but it shouldn't have. "Thin is sharp" is SO true!

Brian.
 
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