Type of blade grinds

[HKG36]

Im not as knowledgeable on knives as I am firearms.

What exactly do the blade grinds mean?

EX. A Hollow grind.

Is there a list of grinds and the deffinition of them?

 

[STR]

Flat V Grind= Good choice for skinning, and carving with an above average slicing ability. Also offers pretty good edge holding and sharpening ease but only fair to moderate at taking abuse.

Modified V grind= great general purpose grind. Seen often around the deer camps. Perhaps a bit harder to hone than the flat, and slicing ability won't be quite as good. It offers better ability to take abuse by a stronger thicker spine. This grind is sometimes seen in Modified V w/ fullers AKA blood grooves. This has also been added for strength along the spine of the knives to condense the steel by compacting it as this groove was usually done when the steel was near molten. It has been used in both swords and military survival and combat knives.

Hollow grind= offers great slicing ability and easy sharpening with fair edge holding ability, but due to how thin it is it does not take abuse very well. Many can be chipped severely by simply hitting a bone. With proper TLC it can last and perform well though.

Concave grind= is like a full hollow grind. This used to be real popular in the early settler days but isn't seen much today. Ability to take abuse is poor. Edge holding is usually poor also. It slices well when it is sharp.

Convex grind= Strongest and best edge keeping, excellent abuse taker here. Usually seen in machetes, axes, and other big hackers and wackers. Slicing is ok to excellent in the smaller knives though depending on the thickness. Some of the better ones are from companies like Bark River or the older Marbles and Randal knives. Sharpening is harder on these and requires a bit of special equipment. http://home.nycap.rr.com/sosak/convex.htm

Chisel grind= Grind on one side of the blade only like on chisels, and Emerson knives, and serrated edge knives as well as some of the finer carving knives.
Usually easy to sharpen until it is time to reprofile. Resistance to abuse is high usually which is why you find it in working tools, and tactical knives.

Tanto grinds= those like in the old Japanese swords along with the tactical knives offering great tip strength and penetration ability. A bit tricky to sharpen at the tip but offers great edge retention similar to the modified V and pretty much the same strength and ease of sharpening along the length of the blade as the Mod V.

Here are the basic shapes with the exception of the last two I wrote of above. Hope that helps.

 

[Cliff Stamp]

...offers pretty good edge holding ...

The nature of the primary grind has little influence on how long the blade will stay sharp, this is due to the properties of the steel and the geometry of the edge itself.

...offers better ability to take abuse

The nature of the primary grind is one factor here, but how it is applied makes a large difference as well.

For example which takes more abuse a TOPS Steel Eagle or Opinel? Which cuts better?

Note here the hollow grind is far more durable and the convex blade is way thinner and cuts much better.

...condense the steel by compacting it

Forging doesn't do that.

HKG36, in general look not only at the type of grind, but its he nature and use the following few simple rules to get a feel for performance :

-as more metal is removed you lose strength this will make the knife easier to bend, so a thin spine makes the whole blade easier to bend and a thin edge makes the edge easier to ripple, a thin tip is also easier to bend / deflect

-as more metal is removed the cutting ability increases, note the only part of a knife which matters is what the material exerts pressure upon, so if you are cutting hemp the edge geometry is very critical, but if you are chopping soft woods the whole profile is significant

Note how these go in opposite to one another, you can't maximize strength and cutting ability at the same time, you have to decide how much of one you are willing to sacrifice.

The other large factor in performance is balance. You will often hear "perfect balance" or "balanced correctly". This implies is a right or wrong balance but again it is a matter of trade off's.

As the balance point is moved back towards the handle the knife will feel lighter in hand and it easier to swing and manupulate, as the balance point moves out on the blade it gets much more powerful on the swing.

So again you have to find the point at which the power on the swing and the fatigue are right for you. Obviously the stronger you are in the wrist the heavier knives you can use for extended work.

If you use khukuris at all for example all bowies seem like fillet knives in comparison. Even something like the Battle Mistress is light in the hand to me, because it has the fraction of the heft of a large Ang Khola khukuri.


-Cliff

 

[STR]

We are talking generalizations here Cliff. Granted you can have an upswept skinner blade and a drop point hunter with the same grinds and get differing results. Of course there can always be exceptions. I see no need to pick apart every minute detail in a generalized review of blade grinds.

Most all of that info on different grinds was learned and was paraphrased from Jim Mayes book, 'How to Make Your Own Knives', from Chapter 6, Blade Design, sizes, shapes, and grinds. It isn't word for word but basically the same jist. My bad on that as I inteneded to edit that info into the post when I got up this morning but since you have already commented I'll just add it here with my reply.

If you disagree with the above statements take it up with Mr. Mayes. I've found most of the info to be generally true.

There are two type of fullers or blood grooves used in knives and swords. There are the ones that are cut or carved in to reduce weight without significanty affecting the structural strength of the blade (same concept as I beam construction) and there are those that are hammered in during the forging process using a shaped piece of iron to indent into the steel when it is still molten and malable.

The first type is generally believed to weaken the blades it is done on but not enough to take away from the performance but enough to help reduce the weight of the blade to varying extents. This was especially helpful with long swords where weight was an issue.

The second was for many centuries believed to actually create two spines to make the blade more rigid and stronger. When a fuller is forged onto a blade it repacks the crystalline structure and forms it into a flexible spine that reduces weight and gives the sword both strength and flexibility. As for the discussion as to whether any of these statements are true feel free to speak your peace. Stength and rigididy with flexibility is why a fuller was done and many may still believe that to be the case. We are talking about the uses of fullers in mediaval cutlery to the present not about what is true or false. The term 'blood grooves' is not accurate though, as that was not really why these fullers were done. Why would you need blood grooves on a Khukri for example? Many Khukris have them including my own.

 

[averageguy]

The "modified v" grind is also known as sabre or saber ground.

 

[Cliff Stamp]

I see no need to pick apart every minute detail in a generalized review of blade grinds.

It isn't a detail, what I was noting was that the perspective of drawing such conclusions about the curvature is fundamentally flawed. You want to look at it from a point of view of cross section.

Now once you have that down you move on to the finer details, such as hollow grinds, especially the t-bar ones like on the Sebenza tend to wedge more than a flat/convex grind of similar strength.

The second was for many centuries believed to actually create two spines to make the blade more rigid and stronger.

A forged blade with a fuller isn't going to be stronger or rigid than the same blade without the fuller, all the metal removed is going to lower strength / stiffness.

It is trivial to see why this has to be true. Simply extend the fuller in scope and width, keep expanding it and eventually you will get a hollow ground blade. This then is massively weaker than the origional profile.

When a fuller is forged onto a blade it repacks the crystalline structure ...

When you hit steel with a hammer it just induces dislocations in the steel, as will any plastic deformation. The crystal structure is only transformed during the heat treating which will effect the grain size, carbide dispersion and size, as well as the actual base crystal structure.

-Cliff

 

[STR]

Average guy, thanks. That is a detail I should have added. We were just talking about that on another thread the other day and it still slipped by me to put that in there.

The nature of the primary grind has little influence on how long the blade will stay sharp, this is due to the properties of the steel and the geometry of the edge itself.

You are kidding me right? The primary grind most certainly does have more than a little to do with the ability of the blade to keep an edge and how long it stays sharp. Hell, it has to do with how well the blade holds up at all on both the primary grind areas and the edge. What good is a razor edge if it breaks off from a weak blade? Have you ever noticed why the thinner a blade is the more sharpening and touch ups it needs? There is a reason for this.

Properties of the steel also have a lot to do with edge holding as do hardness and on and on you are correct. The strength of the blade behind the edge is also a factor in edge keeping just from a strength standpoint alone. For example: the primary reason why a convex grind is preferred for heavy chopping tasks is because that added strength behind the edge from the thicker more robust blade allows the edge to take more abuse and last longer where a hollow or concave or even some thin flat grinds would chip or break from the stresses. If the primary grind didnt matter for edge keeping there would be no need to have so many different options and grind types because it would be redundant.

It is trivial to see why this has to be true. Simply extend the fuller in scope and width, keep expanding it and eventually you will get a hollow ground blade. This then is massively weaker than the origional profile.

This is only true if the fuller is one that is cut into the steel removing steel from the blade like has been done to lighten the weight. There is no steel removed from the blade on the ones that have this done during forging. The steel is simply crunched up and out and displaced to other areas without being taken out of the blade. The mass of the blade remains the same in this case. The jury is still out as to if this technique during the forging process added strength and/or flexibility and rigidity to the the blade which was the main reason it was done in the first place so it could withstand wacks and abuses better. To claim one way or the other is premature at best as this is still highly debated by many.

Personally it would seem to me that if a warrior class of swordsman and those that made the swords for them were doing something repeatedly over time there must be a reason for it. This suggests to me that they would have tested their products and seen for themselves that it did in fact make the swords last and suck up abuse better when the fuller was added this way to create 'two spines' or they would not have done it repeatedly throughout history. In fact we would probably not even be having this discussion if it didn't prove to them that it worked and was worth the time to do on every sword they made because there would only have been a handful ever made and they would have stopped making them that way. When you are going to the trouble of making a sword from scratch why add steps if it isn't necessary?

 

[Cliff Stamp]

Have you ever noticed why the thinner a blade is the more sharpening and touch ups it needs?

No, if anything it enhances edge retention slightly because it decreases the overall force applied to the blade and thus the cutting is done with more control. In general when knives blunt the steel which is effected is constrained to very light penetration into the edge, about 0.1 mm or less, thus the edge thickness doesn't matter let alone the spine thickness.

Edge angle reduction doesn't tend to cause loss either on soft materials, cardboard, ropes and the like, as you decrease it the performance increases, you can cut more material not less. As you progress to heavier work, impact and metal cutting you need heavier edge angles to prevent rolling, but this has nothing to do with the primary grind.

This is why in old axe books you will see references to adding a few passes at a high angle, 30+ degrees to the final edge of an axe. Now if you want to talk about edge durability, then the primary grind comes into play, but the nature of the grind is as I noted more critical than its curvature.

The primary grind is only relevant in regards to edge damage in really heavy work, batoning, chopping small dead limbs and similiar which can actually ripple the edge, and it matters first how thick the edge is behind the bevel, again not the curvature of the primary grind, but its extent.

Where the curvature comes into play is in extreme situations where the damage is so severe it exceeds the edge toughness and you get damage creeping up into the primary grind. In these cases hollow grinds are problematic as they provide the least support and convex grinds the most, but note this is constrained again to an issue of thickness not simply curvature.

You can easily pick a low sabre hollow grind which has much more edge support than a high convex grind. Look at the cross section first for strength and cutting ability, not the curvature.

For example: the primary reason why a convex grind is preferred for heavy chopping tasks is because that added strength behind the edge from the thicker more robust blade allows the edge to take more abuse and last longer where a hollow or concave or even some thin flat grinds would chip or break from the stresses.

Actually, that isn't why convex grinds are used. Axes made for hard woods for example have primary hollow grinds, only softwood axes have convex primary grinds. The reason the primary grinds are used is due to the wedging effect I noted. Soft wood axes need convex grinds to keep them from binding in the wood.

If the primary grind didnt matter for edge keeping there would be no need to have so many different options and grind types because it would be redundant.

No, they are needed, just not for that reason.

This is only true if the fuller is one that is cut into the steel removing steel from the blade like has been done to lighten the weight. There is no steel removed from the blade on the ones that have this done during forging.

Strength isn't linear in all dimenstions, it is above linear along the axis of deformation. Take a butter knife and bend it across laterally and then vertically.

Even though the cross section of the knife is the same in both, the strength is many times greater in the vertical. Any adult man can bend it trivially laterally, it is *very* difficult to do it vertically.

If you forged out a large hollow in a blade and for example make the blade wider as a result with the same spine thickness it would be weaker laterally than the same blade with out the fuller.

If you forged out a fuller and made the blade thicker by hammering out an I-beam shape then it would be stronger, you could also of course just take a large enough piece of steel and stock grind out the identical shape.

When you are going to the trouble of making a sword from scratch why add steps if it isn't necessary?

There are lots of reasons why something was done in the past which are not relevant today, like the old joke about the woman cooking a roast.

A woman cooks a roast and chops the end off, her husband asks her why she does it, she says her mother always did it, there must be a reason and hell it works, the roast is great.

Time passes and months later they are at her mothers who is cooking a roast and is doing the same thing, the husband still being curious asks again, and again get the same answer.

Finally with his curiosity peaked they take a drive out to her grandmothers and he is barely in through the door when he starts asking about the roast.

The old woman cocks her head to the side with a puzzled look on her face "Because the roasting pan was too short."

-Cliff

 

[STR]

Ok, so all the ancient metalurgists and sword makers knew nothing and you do. I get it now. It is a shame they didn't have you there to coach them on how to do things right isn't it Cliff?

Who brought up laterally forcing the blade? I didn't. I'm talking about strikes, wacks and chopping strength not side forces. If the fuller makes the blade more flexible then obviously it isn't designed to increase lateral strengths in the steel.

As for small thin blades cutting better. I didn't say they didn't cut better. They don't cut as long because they lose their bite faster. Anyone can verify this fact in their own kitchen knives. It doesn't mean they can't be forced into something because they can due to their thinness but they don't cut that well anymore.

This is why in old axe books you will see references to adding a few passes at a high angle, 30+ degrees to the final edge of an axe. Now if you want to talk about edge durability, then the primary grind comes into play, but the nature of the grind is as I noted more critical than its curvature.

The only reason this is suggested is to help the axe penetrate better so it takes out bigger wedges faster with less wacks. This can actually weaken the axe over time though if it isn't done right. I think I said this also in a different way.

The primary grind is only relevant in regards to edge damage in really heavy work, batoning, chopping small dead limbs and similiar which can actually ripple the edge, and it matters first how thick the edge is behind the bevel, again not the curvature of the primary grind, but its extent.

Isn't that exactly what I said?

Where the curvature comes into play is in extreme situations where the damage is so severe it exceeds the edge toughness and you get damage creeping up into the primary grind. In these cases hollow grinds are problematic as they provide the least support and convex grinds the most, but note this is constrained again to an issue of thickness not simply curvature

You can easily pick a low sabre hollow grind which has much more edge support than a high convex grind. Look at the cross section first for strength and cutting ability, not the curvature.

I don't know where you get this 'curvature' and the 'nature' of the grind, and 'cross section' terms from or why you feel the need to even bring them up because they are not relevant to this thread on info about the basic grinds anyway. I never mentioned anything about these terms in anything I said. Everything you wrote above just confirms what I already said in my last post so where is your difference of opinion to warrant a rebuttal? You are trying to make it sound like you differ in opinion with me but what you wrote is pretty much what I already said. Sounds like back peddling to me.

And by the way, I grew up in hard wood forests. I never knew anyone that used or owned a primary hollow grind axe nor did we want one. Several in my family were loggers in West Virginia and Pennsylvania and only used convex grind anything for their jobs. This picture below is the best way to show why even if the comparison blade isn't a hollow grind. Convex axes hang up less plain and simple especially in wet green wood. A convex grind tends to act as a wedge, parting the material being cut, and reduces friction or drag created by the wood, but more importantly the convex grinds also tend to have a longer usable life than any hollow grind. A full convex grind will cut just as well after years of use, as it will when brand new. This is pretty darn important to people whose tools are needed for their jobs.

 

[Cliff Stamp]

Who brought up laterally forcing the blade? I didn't.

Yes you did :

"Stength and rigididy with flexibility is why a fuller was done ..."

Being rigid means the resistance to bending.

It doesn't mean they can't be forced into something because they can due to their thinness but they don't cut that well anymore.

This implies they go blunt faster in general, they don't for reasons I noted.

The only reason this is suggested is to help the axe penetrate better so it takes out bigger wedges faster with less wacks. This can actually weaken the axe over time though if it isn't done right.

The secondary edge bevel is added to remove any possible burr and greatly raise the edge durability, it is also a v-grind and not a convex bevel. It does reduce penetration not increase it, but not significantly as the bevel is so narrow. It doesn't weaken the edge, it strengthens it.

I don't know where you get this 'curvature' and the 'nature' of the grind, and 'cross section' terms from or why you feel the need to even bring them up because they are not relevant to this thread on info about the basic grinds anyway.

Hollow, convex and flat are simply diffent curvatures, I used nature instead of saying hollow/convex/flat each time. Cross section means the thickness of the steel, it is relevant here because that is the viewpoint from which you should start with, not the curvature.

As for edge damage, you started off saying things like :

[hollow grind]

"Many can be chipped severely by simply hitting a bone."

As I noted if the edge chips is dependent on the thickness and grind of the edge *not* if the primary grind is hollow / flat / convex.

TOP's knives for example have primary hollow grinds but can be used to cut heavy bone because the edge is quite heavy in cross section.

Again, look at the cross section and not the curvature.

I never knew anyone that used or owned a primary hollow grind axe nor did we want one.

Primary hollow grinds are really common, note all Gransfors Bruks axes are ground this way, and lots of people use them and speak well of them, all cheap hardware store have them primary hollow grinds, a full convex grind axe looks like a splitting wedge.

If you check "The Axe Book" by Cook his "perfect" axe has a hollow primary grind, he describes all axes of this profile with no mention of a convex primary grind for anything. But there were different axes used outside of the states.

-Cliff

 

[STR]

Ok then, so let me get this straight. Taking steel off a blade to make a fuller weakens it, but taking steel off an axe strengthens it. Which is it Cliff? I don't know where you pull this stuff out of sometimes but I have a good idea. I give up on you, I've wasted enough energy on this thread. It was supposed to be a helpful aid for someone that didn't know much about basic grinds by giving him a starting point and basic history of the uses of different grinds and you turned it into the science of a blade shape according to Cliff Stamp.

 

[Cliff Stamp]

Ok then, so let me get this straight. Taking steel off a blade to make a fuller weakens it, but taking steel off an axe strengthens it.

Yes. When you apply the secondary edge bevel to an axe as noted in the above, at a very obtuse angle the edge durability increases even though you are removing metal. Of course you are weakening the edge slightly laterally but by a trivial amount. Look at the percentage change in cross section from the point of view of what is being changed, the very edge bevel and then the blade profile as a whole.

To be clear if you were to take a bowie with a 10 degree edge and reprofile it so that it had a 20 degree edge, the edge would be *FAR* more durable. However if you then flexed it it would be *slightly* weaker, the change in laterial strength is pretty much insignificant as the percentage change in cross section of the blade is a small fraction of a percent.

However the change in edge durability is many to one because the percentage change in cross section there is 100%.

-Cliff

 

[jungle]

Good points all Mr. Stamp. Thanks for taking the time to share them.

 

[STR]

I see. I have had to re read your descriptions a few times to try to follow you. It is hard to know where you are coming from at times Cliff. Pics or drawings would help a lot. I want to understand what you are describing and I think I have it on that last post. It would be weaker laterally because it is thinner but you content it is stronger still than the thicker edge which loses me somewhat as to how.

When I think 'cross section' in my mind I think of the blade cut in half looking at it from the tip or point back. Is that where you are in your head? Because if not you lost me.

 

[Cliff Stamp]

Pics or drawings would help a lot.

The one in the middle bottom shows a steep secondary edge bevel, even though metal has been removed the edge is way stronger because the angle has been raised :

http://photobucket.com/albums/y269/CliffStamp/misc/?action=view&current=secondary_edge.gif

The blade as a whole loses some strength with the loss of metal, but a trivial amount, near impossible to measure and usually ignored. It takes a massive amount of sharpening to actually effect blade properties as a whole.

When I think 'cross section' in my mind I think of the blade cut in half looking at it from the tip or point back.

Yes.

 

[AcesAndEights]

I must say you guys have a mighty fine pissing match going on here.

 

[Anarcus]

I must say you guys have a mighty fine pissing match going on here.

Yes but it is important to acknowledge that the ph of the urine also plays a contributory factor in making the little blue stones erode.

Splash back will be lessened by the jet angle as well as flow rate reductions.

Got to love the man

 

[Practical Use]

My goodness, I really just wanted to know if the knife would cut.

 

[STR]

Cliff and I actually communicate quite well. One thing about Cliff, he can take it as well as dish it out and he is very mature and calm for the most part in his responses usually even after being chewed on for a while.

Which in it's own kind of weird way is quite refreshing here really as it gets uncomfortable for all of us when it gets 'adversarial'. My apologies if it seemed that way here. Sometimes it appears that way in the written word and it isn't the tone intended so it is hard to read into it for sure at times. But I assure you Cliff and I get on well enough for the most part. At least I think we do. I have no issues with Cliff really that have not already been said pretty much to his face and if he had any with me I'm sure I'd hear about it. I don't agree with him sometimes and happily make that known but X- President Clinton doesn't agree with George Herber Walker Sr. either and they are friends.

Again I'm sorry if this came across as a pissing match. It is all in good fun really and I really am trying to understand where Cliff is coming from in this to further my own knowledge, not be a total smart a$$.

Thanks Cliff.

I think I follow what you are saying now. I'm still not sure I agree with you on all points but am willing to stop at this and agree to disagree and move on. My basic tennant as a history buff was to give a simple historical perspective without judgements but it got off some. My bad if it soured things a bit.