Chisel Grind...Why?

Bubba's explanation makes sense to me as well, though I've got to confess I wouldn't be surprised if the opposite were true - I simply don't know & don't claim to. I was surprised a bit by Skimo's post/reply about trolling. I'm sure I'm just not aware of some history here or something, but just reading it isolated in this thread made the reply seem a tad...aggressive. Even if Bubba is 100% wrong, he believes he's right...so why is being possibly misinformed "trolling"? And at the risk of sounding even less cool than I do already, isn't trolling done on a boat with a small motor while fishing?...sorry Skimo, I'm the Dad who tries to act cool in front of my kids' friends by saying "isn't that rad?". Anyhow, I would like to know which of you is really correct as I've often wondered about chisel grinds myself, but not enough to actually research it myself - thanks for the neat-o thread OP.
 
They don't cut as straight? I don't know if the whiskey has already made the rounds, but you can "sight in" a chisel ground blade far easier than a blade that has been ground on both sides. For whittling and woodworking, I far prefer a chisel grind. If you are following the lines of the wood, like with walking sticks and rustic furniture, a double bevel can get sucked into whorls and imperfections in the grain, particularly when removing bark and sapwood. I experimented, and maybe it's just me, but on the same piece of wood the chisel grind left me with no nicks to sand out of the finished project, unlike the other blade. Frankly, let's look at the word "chisel" ground, as in "made to look a bit like a chisel, the premier woodworking instrument since man first turned metal into a tool." Choose the right tool for the right job, and for me that is my EDC in my front pocket, and a Boker War Toad on my belt for making walking sticks while I watch my kids at the playground. I don't particularly like chisel grinds or friction folders, but that one is interesting and useful enough to get the job done and not get me in trouble with the soccer moms.
 
This thread is going to roll!
This might help; the chisel grind is a specialized blade. Use it for those intended purposes; some kitchen work or basic cutting.
About Phill Hartsfield. Phill told me the Japanese style blades he made were, jinto, blades for battle. The chisel grind is not used on the battlefield for utility.
 
It's not about being right or wrong really. I was just offering opinions based on the geometry and physics. Having more material backing an edge and tip is always a good thing if strength is a primary desire. Grinding only one side of a blade blank is always going to give you comparatively more material backing. But debating about blade designs and pros and cons can't really match real-world experience with chisel ground blades, of which I have none other than working with standard chisel tools for home utility tasks. If you try the blade style and it works for you better than something else for the types of tasks you typically perform, then it is of benefit. That's really all that matters in the end. But you won't really know for sure until you try the design. That will deliver the verdict for you.
 
I'm pretty sure its the inclusive edge angle that determines strength and stability, regardless of whether it's ground from one side or both.

~Chip
 
You can't have an opinion on physics. It just is.

The case appears to be what is stronger; a right angle triangle or an equilateral triangle.

Putting my opinion on my sleeve I'd have to side with the equilateral choice.

While in reality the difference may be so small that it's inconsequential.
 
A chisel grind is just another way of putting an edge on steel when it comes to pocket knives, imo. I suppose if I had to make very precise and controlled cuts, I might prefer a chisel grind because the flat would show exactly where the edge is against the material. Shears and scissors are two chisel grinds coming together for a clean precise cut.

Just my two coppers for the pot... :)

-Brett
 
Give this a watch and it'll sort things out. :)

[video=youtube;SuAEGXvKeD0]https://www.youtube.com/watch?v=SuAEGXvKeD0[/video]

The most significant reason for a chisel grind is when you want the centered axis of the edge canted relative to the handle and/or for doing flush paring cuts. Your possible angle of approach is skewed depending on which side you cut from.
 
FortyTwoBlades said:
Give this a watch and it'll sort things out. :)

[video=youtube;SuAEGXvKeD0]https://www.youtube.com/watch?v=SuAEGXvKeD0[/video]

The most significant reason for a chisel grind is when you want the centered axis of the edge canted relative to the handle and/or for doing flush paring cuts. Your possible angle of approach is skewed depending on which side you cut from.
Click to expand...

Yes, thank you fortytwo, I was looking for this video to post.
A chisel grind is not stronger inherently.

As a woodworker, I love chisel grinds. I find the utility consistently evident for all sorts of tasks, with no noticeable disadvantages.
 
Lycosa said:
Yes, thanks for this^
Convex grinds are stronger, no?
Click to expand...

My understanding is that a convex grind is stronger than a flat grind. This is because, assuming the same blade thickness and grind height, the convex is always slightly thicker in cross section at any given point. That means more steel to reinforce the part doing the work. The real mastery in convex grinds is in achieving the benefit without buggering up the cutting geometry (or indeed leveraging convex geometry to improve cutting on some tasks).

Good thread.

I don't have much experience with a chisel grind but I can certainly see their value, for field maintenance alone.
 
Chris Larrikin said:
My understanding is that a convex grind is stronger than a flat grind. This is because, assuming the same blade thickness and grind height, the convex is always slightly thicker in cross section at any given point. That means more steel to reinforce the part doing the work. The real mastery in convex grinds is in achieving the benefit without buggering up the cutting geometry (or indeed leveraging convex geometry to improve cutting on some tasks).
Click to expand...

And you don't "bugger up" the geometry by having the same edge angles. And for a given edge angle....convex is thinner than flat.

Since we are being all about geometry and reality and stuff.

Of course that all goes out the window once you say "convex is thinner."
 
Curves meet an an angle determined by their tangents at the point they meet.

tangent_zpsv4neo5ta.gif


tangent2_zpskzpnsnza.gif


Red line is tangent to the blue curve. Reflect it all over a line passing though A (the green line I added), and you have a convex edge and a flat edge that have the same angle.

And the flat is thicker.

I'm sorry. It's mathematics.
 
marcinek said:
Curves meet an an angle determined by their tangents at the point they meet.

tangent_zpsv4neo5ta.gif


tangent2_zpskzpnsnza.gif


Red line is tangent to the blue curve. Reflect it all over a line passing though A (the green line I added), and you have a convex edge and a flat edge that have the same angle.

And the flat is thicker.

I'm sorry. It's mathematics.
Click to expand...

Apology accepted :p
Very good point and thanks for the diagram. Am I right in thinking the addition of a secondary bevel on the convex changes this? I realise it changes the conversation from being about the edge to being about the grind more generally. I've done a crappy diagram for my own reference but I clearly haven't had enough coffee today :)
 
Lycosa said:
But, the "apple seed" is curved line, not straight. I'm confused.
Click to expand...

The blue part is curved. And you TRY to avoid rounding over the very edge of a convex edge. You round it over, you make it dull. That's what dulling is.

So you have two curves that meet at a point. The angle between those curves is the angle at which the tangents to those two curves at that point meet.

Its really the only way to cross sections of grinds having the same edge angle.

You can compare the cross sections of grinds holding stock thickness constant, but at that point all you are saying is that more obtuse edge angles have a thicker cross section than more acute edge angles.

Hell I can have a v grind thats 175 inclusive. Its has a thicker cross section than a 30 inclusive v grind, but its cutting geometry, as Chris put it, has been buggered.
 
Chris Larrikin said:
Apology accepted :p
Very good point and thanks for the diagram. Am I right in thinking the addition of a secondary bevel on the convex changes this? I realise it changes the conversation from being about the edge to being about the grind more generally. I've done a crappy diagram for my own reference but I clearly haven't had enough coffee today :)
Click to expand...

Thanks. Hate to turn this into math class!

But drawing some pictures for yourself helps!

They are an abstraction of what is really going on at the edge, but they illustrate the concepts.

And, just for the record...I take my v grinds and convex the edges by knocking off the shoulder. I love a flat primary/convex edge grind.
 
I like chisel grinds for special tasks, but they are by no means stronger than a dual-ground blade.
Easier to sharpen? Yes.
More precise? Generally, yes.
Easier to grind/re-profile? Yes.
Stronger? NO.

If nothing else, the issue with a chisel grind for me comes in when you cut anything that is semi-abrasive, or is generally very tough and fibrous. The edge then has some lateral force put on it, or the abrasive material will start to fold the edge over off the flat side of the blade. I have had it happen to me a few times, and it's why I don't carry a chisel-ground knife as a main blade anymore.
That, and a chisel-ground edge is a little more prone to being rounded out than one that is dual-ground, just because the steel on the flat side is not kept at a consistent angle over time, like you do when you sharpen a knife that is dual-ground.
I hope that makes sense. It was kind of hard to put into words accurately.

I really like convex edges for a lot of reasons, but they are a pain to sharpen because you have to consistently remove metal from the entire convex surface, or else your blade will gradually become a steeper and steeper angle on the primary bevel.
You have to do the same thing for flat-ground bevels as well, but they are easier to do since there are a plethora of systems that can set a standard angle for a flat plain...not so many that can do a curve...
 
Convex grinds also have much less resistance while cutting heavier material, and keep a more consistent dispersal of force behind an edge than a flat grind does. You can't just focus on how much steel is behind an edge. You also have to look at how the force from cutting and impacts is being dispersed across the steel behind the edge.

Plus, not all convex edges follow the same, or even a regular, curve. I know some people elongate the curve near the edge to make the blade itself thinner there, and then broaden the curve as they go out to make the thickness of the blade increase more quickly, while still having a thing edge, which is nearly flat-ground.

There are a ton of factors with convex-ground blades, and the real issue with them is that every one is going to be a little different since human hands are doing the grinding in most cases.
 
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