Dagger Geometry Questions

[TIZWIN]

Hey hey guys...as a consumer rather than a producer, I rarely visit this sub-forum. However, recently I have been curious about the blade geometry of double-edged daggers. I thought some folks here might help me out.

Basically, I'm wondering if a double-edged "stilletto," or "dagger," could ever be a good slicer. I know that generally they are made to pierce more than slice.

Is the diamond-shaped cross-section inherently contrary to slicing? Can a dagger be ground to serve as both a slicer and a piercer? Is it due to the width of the blade, or the thickness of the stock?

Consider the classic Fairbairn/Sykes dagger. It has a reputation as being a poor slicer. Perhaps this is due to the sturdier construction of the earliest WWII knives, because the NATO marked, 70's era pattern 3 F/S of mine can actually take a reasonable edge. But it's blade is a rather thin piece of steel, and definitely not hand-ground. It bends readily. Is the thickness of the earlier knives the main reason they supposedly take a poor edge?

Any thoughts on dagger construction, and grinding would be appreciated.

 

[bikermikearchery]

Look at some historical knives. Medieval eating knives were typically double edged. Davie Crockett was a renowned bear hunter and he carried a double edge knife. Both of those examples were used as utility/ slicing knives.

 

[the possum]

Consider this-
Go to the wilderness section here, and you'll find all kinds of praise for the slicing ability of Moras. The grind on those generally goes less than halfway across the blade's width. You could grind a second edge onto the spine without changing the geometry of the existing main bevel/edge.

I generally see more problems with the thickness and geometry at the edge of most knives, rather than the spine.

 

[Jared Stenoien]

Straight edges don't slice as well as curved ones, it still comes down to the profile.

 

[sunshadow]

Someone's sig line is that steel doesn't cut, geometry cuts, I forget who it is, but it is absolutely correct. many daggers if they are real have a relatively steep angle of the edge bevel which gives huge stiffnes and strength for punching into/cutting a resistive object like a chest cavity . Yes you can get the edge to a really clean polished smooth line that will look like flaked glass under a microscope, but as soon as you have parted your material with the concentration of force along that line you are suddemly trying to stuff a huge wedge in behind it. Great if you are trying to create a sucking chest wound through a steel covered rib cage, but not so good if you are trying to make transparent slices of a tomato without tearing them. The reason a straight razor works so well is that the edge geometry is super thin, it takes almost no pressure to push a straight razor through something and there is almost no drag. A cold chisel has a 90 degree edge angle for a reason, it needs to be sturdy to do its work, it doesn't have to be particularly sharp. WhenI'm sharpening a chef knife for a professional chef I try for something in the neighborhood of a 7 1/2 to 10 degree included angle for fine cutting knives, about 12 -15 degree for general purpose knives. The Mora knives that were referred to have about a 14 degree included edge angle if I remember correctly, and you are supposed to sharpen them by laying that bevel flat on your stone so that bevel is maintained. I will probably cheeze off a bunch of folks by suggesting that a dagger was not really a general purpose utility knife, it was a specialized tool for killing. Most folks in the middle ages who carried a dagger also carried a single edged plain utility knife for eating, preparing food, etc. For reference look at the Museum of London book "Knives and Scabbards" (I am currently trying to create a metallurgically correct replica of several of their finds)

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