Swedge Grind

[Donald]

Why do the Zero Tolerance models have a swedge grind? What are the advantages and disadvantages? I can obviously see the pictures, but cannot for instance tell if this is flat all the way to the edge without a separate edge face, or how it differs from a saber grind.

I also do not know how, of if, this relates to a, Swedge, an iron chisel with a beveled edge, used for making the groove round the shoe of a horse; or a ‘swedge,’ ‘crease,’ or ‘concave tool,’ a mold through which the hot bar is pulled by the smith, whilst it is hammered by the striker.

In short, I would appreciate some clarification. Thank you.

 

[Cliff Stamp]

Donald:

<font face="Verdana, Arial" size="2">What are the advantages and disadvantages?</font>

They increase penetration by both reducing the cross sectional area (small effect), and by allowing the blade to cut on the top as well on the bottom (huge effect). As well they allow you to drive upwards and/or turn on a stab after the initial penetration much easier than a blade with a full spine.

They also provide another cutting surface which can be used in self-defense applications as well in regards to utility for heavy impact work where you want to save the primary edge, or the reverse if that is your preference.

As for the downsides, they lower the strength of the tip, how much so depends on how deep they are ground. They also hinder using the blade for a lot of applications such as a draw knife, and a splitting wedge and overall increase the damger of use.

They also tend to make the blades look "tactical" and like "fighters" which is a $good$ thing considering the current market.

They usually don't have secondary bevels unless you are taking about swedges so deep they are actually approaching being a dual edged blade.

-Cliff

 

[Donald]

Thanks Cliff. It appears I phrased my question poorly, even if I got a good answer.

Jerry says, “2/3 grind with swedge grind,”and “zero edge geometry.” Upon more careful review, I suppose I met to ask about the significance of the 2/3 grind with zero edge geometry. What are the advantages and disadvantages? Is this like a combination between a saber grind; and a Mora knife where the edge face is essentially 2/3 of the blade? How does this compare to a regular flat grind?

In the event that I am not expressing this clearly, I am trying to ask for more details regarding the sharp part, the cutting edge of the blade.

Thanks.

 

[Cliff Stamp]

Donald:

[2/3 grind with zero edge geometry]

<font face="Verdana, Arial" size="2">What are the advantages and disadvantages?</font>

A sabre grind is just a partial height grind. The primary grind is not the full width of the blade. It can be any kind of curvature, flat, convex or hollow.

On the positive, a sabre grind is stiffer than a full height grind. It is also a lot stronger, both in regards to full lateral strength of the blade as well as edge durability. The reason is just an increased cross-sectional area.

For the exact same reason, a sabre or partial height grind, cuts at a lower level than a full height grind. The only cutting advantage in that full grinds on thin stock can cause excessive binding, but if this is the case you are better off with a different geometry like the convex/hollow/convex, or hollow/flat of hatchets and 'hawks.

As for "zero edge geometry", it is the optimal profile for cutting ability. When you bleed the secondary or edge grind perfectly into the primary grind, it creates a very low drag profile and thus allows a smooth cutting ability.

On the negative, it may be a bit confusing to sharpen such blades as because they don't actually have a distinct bevel, you may be left wondering on what part of the knife do you use the abrasive on.

-Cliff

 

[RokJok]

Quick & dirty answer (not nearly as exhaustive or as elegant as Cliff's):

The primary bevel grind consumes 2/3 of the total edge-to-spine dimension and leaves a ricasso for the remaining 1/3.

The advantage of the 2/3 grind would be a somewhat stronger blade in the absolute extreme limit. More of the blade is at full-width of the stock. On a full flat-ground blade, the only point in cross-section that is really full width is the spine. Of course, with INFI the difference will probably never be noticed under human power.

The disadvantage is extra weight and that there is blade height that is not contributing wedging action against whatever you are chopping. But that upper 1/3 is also not contributing friction to the surface of whatever you are chopping. So there is some balancing of forces going on there.

I will also defer to Jerry, Cliff, and the others here who have more comprehensive or contrary information, since this is just what I see thinking about the grinds.

HTH,
Greg

 

[Donald]

So reading between the lines, the 2/3 grind is to leave a little more steel for strength in the spine to make up for the thinner stock. With the thinner stock the grind will result in an angle approximating the angle of that of the thicker stock, yet have zero edge geometry for better slicing, especially in softer materials. At least it appears that way if you graph it out. (I note that I edited the angle to more or less the same, because after re-graphing it on makeshift paper it is difficult for me to tell the exact angles without more careful measurement.)

In harder materials the effect would be harder to tell, in that the initial cut would be good, then the thicker spine would be reached, but binding might be reduced.

The knife will be sharpened by abrading the whole 2/3 grind area of the knife, which is one reason these knives could not be coated. This zero edge geometry would also improve the cutting or slicing ability. It would leave a very fine edge that INFI steel can handle even on a larger knife that will be used in chopping.

Lastly, the lesser weight of the knife might result in carrying a longer knife which would give the user more leverage. Further, any reduction in chopping ability from lesser weight for the same length would be compensated for by not having to carry so much weight to the cutting area. I imagine most persons would generally walk more than they would chop, unless out testing a knife or cleaning an area.

[This message has been edited by Donald (edited 06-19-2001).]