Thickness impact : resistance or slicing ability ?

J

Juicytarget

Joined
Mar 4, 2018
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167
Hi guys,


I'm following a custom maker who's using various lengths and thicknesses.

In fact, i was looking at a high saber gind (the top flat part of the blade is like a bit less than one third of the height wich is 36mm), and i wondered, do you loose that much slicing ability by gaining thickness ?

On something like an "outdoor" multipurpose blade of 130mm, with the grind i described, will you loose that much cutting ability by increasing your thickness by one millimeter compared to the solidity increase it represents ?

if you take a 4mm or a 5mm blade, will the slicing ease be that much different with the same grind ?
Is the extra mm worth ?



thanks for enlightening me guys !
 
Many "bushcraft" knives are produced at spine thicknesses of "0.160" (~4mm) or more. Note, batonning is/may be required. Five mm (~0.200") is certainly not unheard of, for heavier woods duty, but works great as a pry-bar.
Common EDC knives (casual or office use) are usually 0.125"...and sometimes 0.140". Maybe okay but it won't slice an apple in the lunchroom very well. More likely to wedge it and snap it halfway thru.
Kitchen slicing blades, OTOH, often run in the range of 0.060"-0.080" spine thickness. Blades in this range cut apples very well.
One of my fixed blades carried for EDC is 0.085" spine with a 3" blade. Another is 0.140" thick spine for the same blade length...both are flat grind. One slices an apple; the other wedges and breaks it off halfway through.
You can try to have the best of both worlds by copying the ideas of CRK... the "common" large Sebenza uses a hollow-ground blade of 0.125" which allows some rough treatment, but at the same time will slice the heck out of an apple due to the hollow-grind nature of the blade contour as you go up from the edge to the blade top.
I like flat grinds and spines of 1/8" MAX width for EDC...little or no bushcraft expected.
For casual carry, I prefer about 0.110" and flat ground blades. Note, that as you get too thin, the blade-smith will a nearly impossible time trying to hollow-grind it...and will reasonably suggest a flat grind.
In order to do it "right"...you really should fine-tune your requirements, based on your projected use of the knife.
 
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Ok, i dont want to cut apples all the day but i think that a Hollow ground on a "bushcraft knife" wouldn't be that much of a good Idea since it's suposed to be more fragile (even if better at cutting) and you certainly don't want something fragile for small battoning / chopping. (I may be wrong but i find most hollow ground on "slicers" and a never did on something supposed to be hit)

I wouldn't want to cut trees with a knife like that but do battoning on 3 inches diam. Pieces of wood.

Still, 4mm would be ok for general purpose ?
 
I would vote full convex grind in 4mm. That sounds good to me. Between FULL FLAT GRIND and FLAT SABER GRIND.... I would go with full flat grind. Saber grind doesn't do it for me. I have yet to snap a blade in half.
 
IMO, there are less expensive, high value knives that you can accumulate and see the difference in blade width for your purposes. Why not try them out, and then spend the big money on a custom after you figure out what characteristics you prefer? Morakniv has slightly different thicknesses on their knives. In folders, the Opinel's are often overlooked (and why I now prefer a thinner blade and fatter handle for general duty).
 
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General rule of thumb, thinner cuts better. That's why all those traditional knives are thin. But rules of thumb can poke ya in the eye :)
 
Thickness is in cubic proportion to stiffness so a thicker blade will resist flex/bending that much more than a thinner blade, but a difference in stock thickness of 4-5 mm on a blade 36mm wide where the primary grind is 24mm wide, the primary bevel angle on the 4mm blade will be ~4.8' and on the 5mm blade it will be ~6' per side. At those thicknesses, you are not talking about a big difference in stiffness, but the spine thickness is FAR LESS IMPORTANT in reference to cutting ability than the thickness behind the edge, i.e. at the shoulder behind the cutting edge itself. The maker could easily grind the primary bevel to be an identical angle for both knives so that they cut equally well behind the edge shoulder but what really matters is what angle/thickness they have right up to the apex. If you grind the 5mm blade to a thinner edge, I would choose that knife over a thicker-edged blade made from 4mm stock. Indeed, if you ground both blades to the same bevel geometry, then the two will effectively cut the same and it is simply a matter of having a slightly stiffer and heavier blade vs a slightly lighter blade that is minutely more flexible.
 
I've used an Old Hickory butcher knife for woods stuff with no damage. It's fairly thin. I think knives are generally made too thick these days.
 
W. Anderson said:
I've used an Old Hickory butcher knife for woods stuff with no damage. It's fairly thin. I think knives are generally made too thick these days.
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This ^
I would start out thin and if you damage or break the knife go thicker the next time until you find out what you like / need then get the custom or what ever.

Also you could go look at Froes at a woodworking tool supply to get an idea of what the actual tool designed for "batoning" looks like as far as thickness. Note the handle allows you to lever with it to split the wood faster with less banging on it.
images-2.jpeg
 
chiral.grolim said:
Thickness is in cubic proportion to stiffness so a thicker blade will resist flex/bending that much more than a thinner blade, but a difference in stock thickness of 4-5 mm on a blade 36mm wide where the primary grind is 24mm wide, the primary bevel angle on the 4mm blade will be ~4.8' and on the 5mm blade it will be ~6' per side. At those thicknesses, you are not talking about a big difference in stiffness, but the spine thickness is FAR LESS IMPORTANT in reference to cutting ability than the thickness behind the edge, i.e. at the shoulder behind the cutting edge itself. The maker could easily grind the primary bevel to be an identical angle for both knives so that they cut equally well behind the edge shoulder but what really matters is what angle/thickness they have right up to the apex. If you grind the 5mm blade to a thinner edge, I would choose that knife over a thicker-edged blade made from 4mm stock. Indeed, if you ground both blades to the same bevel geometry, then the two will effectively cut the same and it is simply a matter of having a slightly stiffer and heavier blade vs a slightly lighter blade that is minutely more flexible.
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This is the kind of answer i wanted tout read, thanks a lot !
 
I can’t leave either thick (5mm)or (thin >.125”)blades behind if I want to be prepared. Same with short (3”) or long (9”) blades. I can always “waste time” sharpening by the creek. But leaving without a hatchet is like leaving without boots or pants. Is 4 knives plus a hatchet too much gear? A weekend could turn into a month pretty fast in the summertime, and the one thing I can’t “make” is a decent knife. Doesn’t answer op’s question, but it seems chiral.grolim already did that, and wanted to add my nickels worth.
 
I understand having not only a knife but also a machet is a basic but when i go hiking i sometimes like to have this multipurpose knife, it only involves me.
So firstly it looks like i should have some nice geometry before thinking about thickness (the less steel behind the edge the better)
Now can you feel the différence between 3,8 or 4.6mm thick ?
I guess, since i'm battoning with Mora pro that 3,8mm would be far enough, and would even make some ok slicer.
Plus the fact that such knife would be made of vanadis 4e, looks pretty though.
 
I'm not clear on your uses but I'll try to offer some of my experiences.

I think 5mm is about as thick as I would want in any knife, even choppers, given the choice. I have a swamp rat (a brand of busse) ratweiler and it's very thick but it's also a very wide blade so it does well to thin the knife once you get to the edge. However, it's a heavy knife for a 7.5" blade but the handle is amazing. If Heavy batoning wasn't something I cared about, then I don't think anything above 4mm is worth it, maybe even 3.5mm. I think 3mm is a great all-around thickness for your basic knife, just don't baton with a club, use a smaller stick and then move to a wedge. However, I've beaten on a mora with 3mm sandvik steel and it's held up very well.

Take spine thickness with a grain of salt because a wide blade with a thick spine can get a nice, slicey edge because of the longer distance to grind it down but the weight can hurt your fine movements some. Similar going the other direction with a thinner spine. Some of the thickest edges have been on some of the "hard use EDC" knives; I actually thought the BM 943 was a horrible slicer, as an example, because of the standard thickness steel but the flat grind starting so low with little blade width to work with hurt it a lot. That's why a lot of the full flat grind spydercos get acknowledged for their great slicing ability, wide blades which a long grind coming to a decently fine edge.

Becker's knives, as a whole, are right around the .2"/5mm range for much of their line and I think that's why they are so well liked.

Where I think thick spines/blades are helpful:
  1. adding weight for a dedicated chopper
  2. more surface area for batoning, eats up the baton less
  3. increased side loading for prying split wood apart, or whatever
  4. being careless with a knife, a lot more steel to work with if/when you damage the edge
  5. FUN, they can be a lot of fun
Lastly, my experience has been that the thick, heavy blades are tiring to wield on a regular basis but the reduced length and straight shape, over a small axe, make them nice and portable. I've started to think machetes and axes were designed the way they were for a reason. BUT, the big blades are a heck of a lot of fun if you want a good arm and cardio workout in the woods.
 
Juicytarget said:
I understand having not only a knife but also a machet is a basic but when i go hiking i sometimes like to have this multipurpose knife, it only involves me.
So firstly it looks like i should have some nice geometry before thinking about thickness (the less steel behind the edge the better)
Now can you feel the différence between 3,8 or 4.6mm thick ?
I guess, since i'm battoning with Mora pro that 3,8mm would be far enough, and would even make some ok slicer.
Plus the fact that such knife would be made of vanadis 4e, looks pretty though.
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Yes and yes, especially in the weight and balance department.

Generally speaking, the scandi grind on moras is not a great slicer when looking at cutting deep into material (think like cutting cardboard) but they work great on wood. However, they work adequately. My preference has gone to full flat grind as an all-purpose, convex or flat for heavy work, and scandi/scandi-vex for wood specific use and ease of sharpening.

As much as I like some of my knives, the more budget friendly, but still not cheap, HK feint has been my favorite in terms of a lightweigt, multi-purpose knife. It's long enough to some trail clearing and light chopping, thick enough to handle some batoning, and fairly portable due to it's size and weight. The rubber handle is also a nice touch and I wish more knives had these as they are pretty shock resistant.
 
Alright alright, how thick would you want such knife behind the edge ?

Again i wanna handle LIGHT battoning and chopping, 2-3 inches wood un the worse possible case (for battoning) and 1 inches for chopping.

It feels like every time i talk about battoning people are like "alright, you mean putting down giant sequoias ?"

No.

And it will certainly be more meat cutting than anything else.

Thanks you guys, be sure all this information will be taken in account :)
 
Also you could go look at Froes
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Go for the froe, bro'. Be a trend setter. The new Schrade makes one for < $30 delivered that you can beat to death. Get a nice custom slicer you can show indoors or out.

But, get what you want.
 
I love hatchets but honestly will likely never carry one ever again. I personally prefer an edc slicer pocket knife, a medium or even small fixed blade and a silky saw. For me, the fixed blade is mostly a food knife that I can bash through wood to get kindling in an emergency so I want something I can baton with. If I didn’t want to have access to that ability I simply wouldn’t carry a fixed blade. I’d just take a couple folders. All that said I’ve never broken a mora at sub 3/32 inch thick and 22 degree inclusive edge but I gravitate toward 1/8-5/32 inch thick knives for this purpose. The izula 2 disappears on my belt.
 
Juicytarget said:
Alright alright, how thick would you want such knife behind the edge ?

Again i wanna handle LIGHT battoning and chopping, 2-3 inches wood un the worse possible case (for battoning) and 1 inches for chopping.
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I'm far less analytical about knowing the measurement behind the edge (don't have a way to measure) but generally it seems like if I can distinctly feel the shoulders of the bevel, running my fingers from spine to edge, then it's too thick, with the scandi grind and the use mentioned being an exception. IMO, it should feel like a smooth transition from primary grind to edge bevel, if I'm using that terminology correctly.

For handling 2-3 inches of wood, without knots or really fibery wood like ash (all over the place by me, and dead from ash borer infestations), you shouldn't need much. A 5" blade so there's a little tip to hit and you're golden. I've used a mora companion on such wood without a problem. I've read that you can use a wedge on the spin of the knife instead of the using the tip as a means to drive it through harder to split wood or wood where the tip doesn't expose enough to hit it with a baton.

These are just my opinions and I've found it more fun to get a knife and test it and then get something else and test that one and see how it all works out. Schrade has a few decent designs in their frontier line for cheap pieces to test different designs if you can overlook some of the blatant copying of other's designs. I like ontario knive from a budget standpoint for nicer made knives than schrade but many I've had are thick behind the edge but are superb after a re-profile. Most of my fixed blades come off of the knife maker's market on the exchange these days though, unless I want a bigger chopper.
 
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