blade grind difficulty?

N

nybble

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Nov 9, 2001
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I hope this is the right place to post this. I would like to know if it is more difficult, in general, to hollow, flat or convex grind a given blade? I mean, all things being the same, if you had to grind the exact same profile in those three ways, would any of them be easier or harder than the others? Or is it sort of whatever you're used to grinding?

And for knives that have a transition (i.e. hollow for most of the body of the blade, transitioning to flat or convex at the tip) - is that particularly difficult as well?

Ok, while I'm at it, are certain profiles generally harder to do? i.e. is a hawkbill harder than a wharncliffe or spear point? etc...

I hope these are OK questions to ask, I really just have no clue as to what goes into the art of blade grinding and am trying to get an at least basic sense of what is harder to do than not. I do not want to be in the position where I ask a maker to do something that I (in my ignorance) assume to be easy only to find out I just asked for the moon to be delivered to me. It happens all the time to me (as a computer programmer) where clients assume some things are easy and some hard - only to have the exact opposite, the things they thought were hard were trivial and easy things took weeks. It really messes up planning. :)
 
I think the questions that you have asked are very good indeed. I am interested in the answers you will get. Since I have no experience making knives I do not know the answers myself.
 
Nybble, I hollow grind for the most part, and find that easiest, for me at any rate. I have talked to those that mainly flat grind, they claim that, easier than hollow. The convex, I wont comment on.
As to what type of blades are harder to grind, I would say the hawkbill, of the three types you listed.
Don't worry about talking to makers. Ask all the questions you want, makers are glad to answer them. If they aren't, find another maker.
An informed customer, is usually a happier customer. That is not exactly the description I mean, but it's late in the day, alzheimers is setting in, so I hope you get the picture.Again, don't be afraid to ask questions of the makers. Thats what we are here for, besides making knives. :D
 
Well said Mike.

This is a question that generates many different answers. Typically when you ask a maker which grind is harder to do he will tell you whichever one it is that he does ;)

Personally, I think there are trade offs as far as which is harder. I think it's a little easier to do the initial grinding with a hollow, but a flat grind is easier to hand sand, so...

Which is "better" is a whole other argument :rolleyes:

Without question if you do one more than the other...you've got practice on your side.

Like Mike said, don't be afraid to ask... :)

Nick
 
My vote:
Hollow grind easiest-work is done against a rubber wheel, which results in less bounce, heat and belt wear. Also, once the grind is established, the hollow provides a trough which tends to keep the wheel in the grind. You can grind with lots of pressure, and have lots of control over the frind line.
Flat grind-next hardest-work is done against a hard, stationary platen. More heat, more bounce and shorter belt life. Finer belts produce coarser scratches than when used on a rubber wheel, due to the splice on the belt and the hard platen. Also, harder to "feel" the desired grind and keep it even when grinding.
Convex grind-hardest-I do this against slack belts, starting with a flat grind. This grind has the least angle at the top of the grind, making it harder to maintain a clean grind line. It's also harder to remove coarser belt scratches with a convex grind, because the pressure against the belt is not even across the blade. The plunge area can be very difficult on a convex grind.

Opinions may vary on this, because, I'm sure there are other techniques used to produce these grinds-My answer is based on my experience in my shop.

Hope this helps,

RJ Martin
 
The easiest grind is the one that you enjoy the most. I like challenge, enjoy pushing the design to the maximum potential.
 
And that modified Price grind of yours sure does that Ed. The grind on my Pronghorn is a work of art. It also looks like it is not the easiest way to grind a blade.
 
Ed: With all due respect, your answer is not an answer to the question asked. Specific questions have been asked here, and, you're just changing the topic.

RJ Martin
 
RJ: Thanks for the comment. I did not mean to change the subject, what you read and felt was my possibly too simplistic statement attempting to place the real issue in the spotlight. A flat grind is simple, until we ask specific questions concerning performance, final edge angle, how to blend into the guard how to maintain tip and edge strength with the nature of the steel and task. The same appleis to hollow grind, there are many ways to hollow grind, some better than others. When it comes to convex grinds, they also can be simple or highly complex.

The novice tends to consider the grinds in simple boxes, Hollow Grind, Flat Grind, Convex Grindand thus place knives in three simple boxes. You would think there are only three grinds. The truth of the matter is that there are as many variations of the three chapters in blade lore as there are makers. When you consider knife makers who think, who test blades, and seek specific answers to the many questions suddenly we have some very complex issues.

The maker who tries to execute a grind on a knife he hates will make,for him, the most difficult knife. For example: When a good man horseback rides an individual horse, blends his ability with the nature of that horse in concert, he will get the most out the horse possible, he will travel further and expend the least energy, both his own and that of the horse. The same senario exists with knives, for some the flat grind is simply flat, no questions asked. If that knife is put to the test both he and the client will probably be disapointed. For the maker who knows the nature of his steel and the variables surrounding the flat grind, the execution of that grind is a pleasure to him and the man who needs a knife. He may make the knife in less time than the novice, ease of execution comes with practice and experience. The questions of why and what for carefully considered and answered by how.

The knives of Richtig were flat, because he started out with flat steel. 50 hears ago he made knives that today still stand in the top 5% level of performance. Was the grind simple? Yes, but blended with a very complete understanding of his steel blended with performance.

When we challenge ourselves, the task is simple for our level of involvement renders it enjoyable and rewarding. When we chose to make many simple knives, the rewards come from without rather than from within and for me that would be the most difficult knife to make.
 
Thanks everyone, it has been a helpful thread to me. I found it interesting to see the differences in perspective between the makers and no consensus! I guess that is the beauty of custom knife makers, everyone has their own strengths and ways of doing things. And Ed's more metaphysical viewpoint was very good to read as well, I really appreciate RJ's call for clarification as I was a little intimidated to do so and the outcome was worth it.

Thank you again.
 
Nybble: Never - Ever be intimidated to ask or challenge. If the person challenged does not accept the question and seek to answer with a satisfactory statement, he wasn't worth the worry. If you don't ask, you will have to find the answer yourself or go without. Every one of us puts his socks on one at a time. Thanks for the comments and the opportunity.
 
Personally, I like Ed's first answers. Most knifemakers have an idea of what their knives should look like when they begin making knives and start grinding with an eye to making them that way. Some like the flat grind for their style of knife; some prefer hollow grinds. Whatever you like best is usually what you become best at doing, simply because you are happy with the process and like the result. There are many who flat grind who couldn't do a decent hollow grind if their lives depended on it, and vise versa. I flat ground a couple kitchen knives once and they really sucked, but I've never had anyone tell me my hollow grinds looked particularly easy to do.

It's really no different than which grind you prefer to buy. Whatever floats your boat is the best, for whatever reason. Whatever you think best is the one you buy most. If after buying those knives for a number of years you decided to start making your own, it's a good bet you would use the same grind as in the knives you bought, and you'd still think that was best. It would be what you practiced at most, and would then become easiest for you to do. In fact, you'd proabably become as pig headed as most other knifemakers and insist that whichever grind you are best at doing is the ONLY grind worth doing at all... :)
 
My kudos to my pal Jerry :D Well said.

Hey Jerry, I heard a rumor that you're coming to the OKCA show this year...any truth to that?

Nick
 
Well, metaphysics aside, the question asked was a technical one, and, I gave the only technical answer. The question wasn't about which grind is preferred by a maker, or, which suits a given blade best, it was about ease of execution.
Grinding against a moving, cushioned convex surface will ALWAYS be easier and more efficient than working on a fixed, hardened surface(flat grind), or a variable surface (slack belt). That's due to the physics of metalworking, and, simple geometry.
So, assuming a maker is competent in all 3 styles of grind, my answer stands. The hollow grind is going to get done faster and with less effort from both the maker and the belt, the flat grind will be next, and, accomplished at a slower metal removal rate and with more belt wear, and, the convex grind will take the longest.

Note, the question was a general one, and, compared grinding the same blade 3 different ways. I can think of no blade shape that would change the order of ease of execution. I can think of several, such as a severe recurve, that would make flat and convex grinds far more difficult than the hollow grind.

We all know that, any good maker can execute any grind he wants(or, for that matter, all three, in combination!!), on any blade, and, make it look easy.
One grind is not more simple or more complex than another, but, the simple fact that the machinery available to produce these grinds is more efficient at yielding the hollow grind than either the flat or convex grind.

RJ Martin
 
Personally, I find the convex grind easiest, but that's just me on my equipment. It's not generally a grind I'm fond of though, except for an edge.
 
i agree with RJ, that from a machining point of view the hollow grind would be easiest to teach to a machine operator. not one of us pig headed knife makers:)
 
Hate to dissapoint you folks but it doesn't take any longer to flat , convex or hollow grind. The degree of difficulty is in the mind and is related to the amount on practice that you have.
 
Hollow grinding may not technically be "easier" for someone who is practiced, and therefore proficient in flat grinding, but it is technically more "efficient". When you flat grind you work on the surface of a belt which is moving over a stationary surface of a platen, creating drag, friction, heat, etc. against both sides of the belt at once, as opposed to a belt running on a moving, rubber coated wheel creating resistance only against the blade being ground.

Also, no one mentioned the fact that using a "serrated" contact wheel improves the grinding effectiveness of the belt. You don't have this option while flat grinding. Ever see a serrated platen? Given equal pressure and time, a serrated wheel will remove metal faster than a flat backing, thus making it technically "easier" (and faster) to grind, depending of course on what "your" meaning of "easier" is.

Therefore, "technically", I agree with RJ. Otherwise, I agree with doing it the way you like doing it to get the results you want.
 
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