Spine thickness?

T

thatsaknife

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Mar 27, 2015
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After admiring all the knives on the board and interweb I went back with a ruler to measure my old knives thicknesses. None of my knives I had growing up were more than 3mm or 1/8 inch thick. Also the 3 knives I have made my self measure 3mm or less. Now this begs a question.What is to be gained by a knife 6 inches or under to be made of more than 1/8 inch steel. I have never broken a blade but also I do not baton wood with a knife so maybe ive answered my own question
 
Hacksaw blade knife. First knife I ever made as a kid. Very thin and flexible



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good question that I'm interested in seeing people's opinions of. I've never made any really thick blades 5/32 is as thick as I've gone but I've also never made anything very large either. I see 3" blades made from thick steel and it just seems like clunky overkill to me. My personal preference is slim and sleek so that's how I like to make them.
 
Thinner = better if you're using it for knife tasks and not prying/twisting etc.

I carry a custom small tanto (sub 4" blade) that's 1/4" thick D2; it's basically a glorified prybar and I use it as such... ;):D:rolleyes:

That said; I have a fixed blade in 1/16" ATS-34 that is a joy to use for actual cutting tasks. :thumbup:

It's all about your P.O.U ya know. :D:foot::p
 
I like rather thick blade stock because I just like it. My 710 has a .114" thick spine and that's as thin as I like to go on that size blade.
 
My Mora Bushcraft Black is 3.2 mm and That is the thickest blade I can ever see needing. My other knives in the 2.5mm range have always been plenty strong for cutting tasks.

The only exception is my BK9 but it's in a different class.
 
Thin knives are slicer but generally speaking when you start desiring a thicker stock for a more stout blade, you're no longer talking about slicing tasks anyway.
 
KennyB said:
Thin knives are slicer but generally speaking when you start desiring a thicker stock for a more stout blade, you're no longer talking about slicing tasks anyway.
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Precisely. If you want your knife to chop, smash, bash etc, then you need thicker. "Survival", "Combat", "Hard use", etc. People like that stuff. Even in folders. So makers make that stuff. Not a big mystery.
 
My guess for why blades on small knives can be thicker than 1/8" is simply user comfort/peace of mind. If the blade is thicker you don't worry as much about accidental breakage, making you feel better every time you use the thicker blade. Sure, it might not slice as well, but it makes you feel better afterwards.
 
Thin stock for me. I can go a little thicker but then it needs to be chisel ground with a zero edge. My preference in fact is a thin blade with a chisel grind and zero edge - great cutting, thin stock, but still very strong.
 
A thick spine is more comfortable on my thumb when carving.
With a wide blade and full flat grind, a relatively thick blade can slice rather well. :)
 
Thicker is stronger.

As stabman points out, how well a knife cuts is, in significant part, a matter of blade geometry rather than ultimate thickness at the spine.

The most popular "hunting" knife before WWII was the Marble's Woodcraft. While it was 6/32" (.1875") thick, it was 1.125 - 1.34" wide and full ground to the spine for most of its length, making it quite acute. It is, for example, significantly more acute than a Survive 3.5 that is 4/32" (.125") thick at the spine.
 
Thomas Linton said:
Thicker is stronger.

As stabman points out, how well a knife cuts is, in significant part, a matter of blade geometry rather than ultimate thickness at the spine.

The most popular "hunting" knife before WWII was the Marble's Woodcraft. While it was 6/32" (.1875") thick, it was 1.125 - 1.34" wide and full ground to the spine for most of its length, making it quite acute. It is, for example, significantly more acute than a Survive 3.5 that is 4/32" (.125") thick at the spine.
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For sure.
I have a knife which is 0.090" spine thickness that cuts far worse than all my knives in 0.125" thickness, because it is a narrow blade with a saber grind.
 
Strider SMF has a spine thickness of 0.190". Many paring knives, OTOH, run from about 0.060" to 0.090" thick. The SMF makes a decent pry-bar; the paring knife does not. Sebenzas and Zaans are 0.125"-0.140", which is my preferred range. I do casual EDC, and have little need for pry-bar action.
 
marcinek said:
Precisely. If you want your knife to chop, smash, bash etc, then you need thicker. "Survival", "Combat", "Hard use", etc.
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Yep.

When you need a knife that will not fail under extreme uses that are not typically referred to as 'slicing' tasks.

The 1/4" thick BK2 has been used to cut through a lawn mower. A Fire Rescue team used a 1/4" thick BK3 to dismantle a Dodge Omni.

Not something you're likely to try with a 'thin' slicer regardless of blade geometry. ;)
 
The chord height of the blade plays a big part in the geometry at a given blade thickness.

Fun fact, the 3/16in thick BK9 has the same cutting geometry as the much smaller bk11 (5/32in thick). So, that means that knives with small chords will generally have thinner spines, due to necessity (at least if they want somewhat common edge geometries).

But, for folding knives, I'm with you. I don't see a need for anything really thick on a folder, simply because my use cases for a folder are light. For any hard task, ill grab a fixed blade, and my favorite thicknesses seem to be between 1/8 and 3/16.
 
stabman said:
For sure.
I have a knife which is 0.090" spine thickness that cuts far worse than all my knives in 0.125" thickness, because it is a narrow blade with a saber grind.
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Common mistake with spine thickness = a knife ground from thicker stock does not cut as well as one ground from thinner stock.

So many other variables as you guys have mentioned, as well as, 'what type of cutting do you do?'
Or more precisely, what type of tasks do you do with a knife?
 
Sonnydaze said:
Strider SMF has a spine thickness of 0.190". Many paring knives, OTOH, run from about 0.060" to 0.090" thick. The SMF makes a decent pry-bar; the paring knife does not. Sebenzas and Zaans are 0.125"-0.140", which is my preferred range. I do casual EDC, and have little need for pry-bar action.
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An SMF can slice very well with a good edge at 20DPS.

I have no issues shaving through phone book paper with my FFG. Cardboard is as easy as I need it to be.
Food prep is a breeze.
Are there better knives? For sure, but you make it sound like an SMF can only pry, which makes me think:

A: You can't put an edge on a knife.
B: You've never used an SMF.

It can also pry and chop, the paring knife can't.....

I would think that as an EDC, as a knife that's in your pocket, some versatility would be a big consideration....
 
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