Thick Blade Geometry vs. Thin Blade Geometry

[iamerror]

Lately, I find myself noticing more the difference thin blade geometry can have in cutting... creates a lot less drag when cutting things like cardboard. But, with a thinner blade you do lose strength. A few things...

1. Has anyone broken a blade, if so, what knife and how did it happen?

2. Is strength the only reason knives are made thicker?

3. Do you think some knives are made too thick? I think the Salsa is great, but it seems like the thickness is a little overkill on a knife this size. Even on a knife like the Delica, the steel seems pretty thick to me. Is this type of thickness really needed on a small folding knife?

Your thoughts and preferences?

[The Deacon]

Lately, I find myself noticing more the difference thin blade geometry can have in cutting... creates a lot less drag when cutting things like cardboard. But, with a thinner blade you do lose strength. A few things...

1. Has anyone broken a blade, if so, what knife and how did it happen?

2. Is strength the only reason knives are made thicker?

3. Do you think some knives are made too thick? I think the Salsa is great, but it seems like the thickness is a little overkill on a knife this size. Even on a knife like the Delica, the steel seems pretty thick to me. Is this type of thickness really needed on a small folding knife?

Your thoughts and preferences?

1. Have never broken the blade on a Spyderco, any other knife I've broken was while doing something that involved twisting or prying.

2. No and yes. As far as the working portion of the blade, pretty much NO, athough there MAY be some specialized instances where the "wedge" action of a thick blade is beneficial. As far as the blade tang, YES, as it gives greater lock strength and/or lock enagement surface. It qlso provides a larger bearing surface for the pivot pin.

3. Yes, I can't see carrying a knife with a 4mm thick blade much under 4" long. Can't see the need for 3mm on sub-3" blades either. But tastes differ, and I know I don't fall into the "mainstream" of Spyderco users. The good news is that Spyderco does offer alternatives. You might want to take a look at the Centofante III and IV. They have the thinnest blades (2mm) of any 3" :spyder:.

[JD Spydo]

I pretty much agree with everything Deacon just said with one exception. I myself have found practical use with thick blades like the one you find in the Manix or Chinook III models for instance. Even the fairly thick blade on the fixed blade Temperance model is very useful but is just a bit more time comsuming to sharpen.

Like Deacon says when you use a thin blade like the one on a C-52 Calypso Jr for instance is to be used only for cutting and shearing only. He is right on when he says that a knife is only to be used for it's intended purpose. The only time I have ever snapped any blade is when I put too much pressure on the tip area of a Spear Point blade or one of like design.

The one advantage that I find in a thicker blade is that you can get away with using a bit more force pushing through a cut. But I can't stress enough that they are still for cutting chores only. JD

[fellyjr]

I pretty much agree with everything Deacon just said
JD, Are you feeling alright this morning?:confused: :eek:
I think you need to check your temperature or something! :p
I just marked today's date on my calendar. :D :D

[thombrogan]

On blades like the D'Allara Drop Point, Manix, Chinook, and ATR, a thick edge may be of benefit (assuming the knife is used as an all-purpose tool), but unless the knife has a steel that can withstand Thomfoolery, I want it thinner than thin. Spyderco's edges tend to be thinner than most other production knife edges (especially in priced-to-own-and-use knives), but they still can be thinner.

The good news is that if the edges don't please you, DMT of Marlboro, MA sells the D8XX 120 grit diamond hone and Tom Krein of Gentry, AR offers a regrinding service for folks who appreciate the magic of high hollow grinds with striking good looks.

[gunmike1]

Once again Thom nails it. For pure cutters I have sent some knives (and been lent some) that Tom Krein has reground to VERY thin high hollow grinds, including a Native, Jess Horn ZDP, Meadowlark, Fallkniven U2, and a Caly Jr. ZDP (Sodak from Blade Forums was nice enough to front me that one, and it should arrive in a day or two). They are all tremendous cutters that sharpen up in no time flat, but they need to be kept straight through the cuts, with no twisting on tough cuts or else you will get some chips. Plus, most were sharpened flat to the stone before going to him and were extremely ugly, and he made them look like factory (and nice factory at that) finished knives, which is nothing short of a miracle on a couple of those knives. For my Manix and most other general use knives I reprofile the primary down to 10-12 per side and then microbevel at 15, and leave it at that. Those knives cut very well and are very durable short of cutting metals.

Mike

[cobrajoe]

I definately vote thin over thick in use for cutting, and I have never broken a blade on any knife.

Let me get this straight though, you think the blade on the salsa is thick? I agree that it may be about as wide as a delica (I don't have them both here, so I'm not completely sure), but the tall flat grind thins out the blade very quickly, and I would never think of prying with the little salsa, but I wouldn't worry about doing the same with the D4.

[Ed Schempp]

Most every production knife I own I reshape the edge. I use a slackbelt and establish a hamiguri or appleseed edge. I can generally thin the edge considerably. I have spoiled a few guys with my sharpening so now they bring most all their knives to me to get the edge thinned out. I recently sharpend a Gerber-Applegate and the sharpening line moved back into the blade 1/8 inch. Now the knife cuts. Thin cuts, a good transistion helps. Spyderco has a reasonable edge to begin with, much thinner than many other brands...Take Care...Ed

[enduraguy]

Even though I dont currently use my Para Millitary, because I carry my Pac. Salt so much, the Para has got the thinnest edge profile I recall seeing on a folder.

[J D Wijbenga]

I too like them thin and reshape almost very knife I buy. Diamonds work well for this. I usualy wind up with an apple seed/convex edge that cuts very nice.

JD

[iamerror]

I have also bought the DMT D8XX and have started reprofiling blade edges but don't think I could do a good job at modifying a blade drastically, such as turning it into a hollow ground. And I am not quite sure I would want that yet.

cobrajoe, were you saying that you would pry with the Delica, but not the Salsa, even though they are similar thickness? About the thickness, the Salsa does seem thick too me, especially when using it for something where you push the blade all the way through, like cardboard. It probably was not intended to be good at box cutting, though.

What are some more of the specialized purposes that a thicker blade will excel at?

[gunmike1]

I have also bought the DMT D8XX and have started reprofiling blade edges but don't think I could do a good job at modifying a blade drastically, such as turning it into a hollow ground. And I am not quite sure I would want that yet.


Since Thom Brogan introduced me to the D8XX I have been in reprofiling heaven, thinning out most every knife within my grasp. That stone is a reprofiling machine, and it eats through any steel you can think of extremely fast. It is the fastest thing for reprofiling short of power equipment. I have a Sharpmaker and the full compliment of grits in the Spyderco benchstones and they do a great job of putting a very sharp edge on the knife for finishing, but the D8XX is a true cutting machine for reprofiling. I agree with you on not adding your own hollows, for that I sent my stuff off to Tom Krein for regrinds. He makes some very nice knives of his own that I would love to get, but in the meanwhile he has been great about thinning out my Spyderco's to very thin and efficient cutting grinds (even though Spyderco's factory grinds are about as good as it gets in production knives in that regard, I am a little extreme in my tastes for very thin edges, as even the Caly Jr. is too thick for my tastes in a precision cutter). He is a great guy, very freindly, knowledgable, and very helpful. He can take the knives that I make look like turds with my D8XX and both drastically thin them by adding in nice high hollows and make them look like new, he is a real artist.

Mike

[iamerror]

Thanks for recommending Tom Krein. That is something I could consider in the future. Is he a member here?

[Harry White]

thombrogan and gunmike -- i recently picked up a DMT D8XX. could you post some basic steps that you follow when reprofiling/thinning a knife edge using this wonder stone. after all, you guys talked me into it!:D (and thank you, BTW).

also, i've heard talk of laying a jess horn ZDP flat on the stones to thin it out. what's involved there and how long does that take?

i really want to put my D8XX to the test, but i'm a little gunshy.

thanks!

[cobrajoe]

I have also bought the DMT D8XX and have started reprofiling blade edges but don't think I could do a good job at modifying a blade drastically, such as turning it into a hollow ground. And I am not quite sure I would want that yet.

cobrajoe, were you saying that you would pry with the Delica, but not the Salsa, even though they are similar thickness? About the thickness, the Salsa does seem thick too me, especially when using it for something where you push the blade all the way through, like cardboard. It probably was not intended to be good at box cutting, though.

What are some more of the specialized purposes that a thicker blade will excel at?
Yup, that's about exactly what I was saying. I guess I notice the grind of the blade sooner than the thickness. My salsa can slice those cheap foam earplugs into 1/16th inch slices that are perfectly flat and round, and none of my other spydies can do this (the lava and raven come close, but they just don't seem to be perfectly flat). I can see where you are coming from though, my D4 seems to go through cardboard easier than the salsa, but I'd like to see how they compare when slicing something like potatoes or carrots that might break before yielding.

As for a thick blade, those seem to be best when the knife is abused. I have a friend that just bought a delica to replace the blade he broke on his leatherman. He was trying to hammer the blade through some electrical cable and the leatherman broke. He also said that his SS delica is probably the thinnest bladed knife he would buy.

[thombrogan]

Harry White,

The side profile (drop point, clip point, wharnie, etc...) won't be changed (unless you want to), but the angle of the edge is thinned out by laying the knife either flat or almost flat and grinding away. I use one hand on the handle

http://www.tntbrogan.com/knives/sharp03.jpg

and the fingers of the other hand pressing the blade into the stone (similar to how one sharpens with waterstones, but with much more pressure).

http://www.tntbrogan.com/knives/sharp04.jpg

Care must be taken not to throw your fingers in the path of the oncoming blade. Louisiana Cook used his D8XX to thin out his Centofante 4 until it was flat ground and then polished out the scratches with progressively finer diamond hones and waterstones. Now it's fragile, but impressively sharp for light cutting.

[clovisc]

1. broke the manix, poking in some old wood that seemed pretty soft. probably twisted it wrong, but... was VERY surprised.

2. sure as hell hope not!

3. for certain. there's a reason i carry my centofante III so much, and use it as one of my favorite food prep knives... :D

[gunmike1]

Thanks for recommending Tom Krein. That is something I could consider in the future. Is he a member here?

Do a search on Blade Forums or google or go to www.kreinknives.net for contact info. I have a thread going right now in the toolshed section of bladeforums with some of his regrinds with pics.

Mike

[Ed Schempp]

Considering the same task every steel has an optimum thickness. If you go beyond a certain point the failure rate increases. Most everyone has a unique set of tasks that they apply the use of their knife. I have some bench knives that I make very thin and leave full hard without a temper. Some blades I prefer a toothy edge and some that I polish. I've made some kiridashi that I took the plane of the grind to the edge and water quenched. There is some very good information about sharpening in this tread. I encourage everyone to experiment and try for a better edge...Take Care...Ed

[gunmike1]

thombrogan and gunmike -- i recently picked up a DMT D8XX. could you post some basic steps that you follow when reprofiling/thinning a knife edge using this wonder stone. after all, you guys talked me into it!:D (and thank you, BTW).

also, i've heard talk of laying a jess horn ZDP flat on the stones to thin it out. what's involved there and how long does that take?

i really want to put my D8XX to the test, but i'm a little gunshy.

thanks!

Thom's pics are great. I reprofiled my Jess Horn ZDP, Native, and Endura Wave flat to the stone. If you do a search in the toolshed section of bladeforums I have a couple threads on the Jess Horn and the Native. It will take some time to reach the edge when you sharpen flat to the stone, as you are lowering the angle from about 12-15 degrees per side to about 7-8 per side. The last bit of steel removal to take the new bevel all the way to the edge takes a long time and can be frustrating, but it is well worth it for the increase in cutting ability and edge retention. You can break it up into stages where you work it flat to the stone for a while here and there, and eventually you will reach all the way to the edge, all the while leaving your existing edge uneffected. Or, you can do like I did and go balls out for a couple (or more) hours and complete the job in one sitting. I recommend doing it in stages, as your hands and wrists will thank you. Also, you should switch to a finer stone (I use DMT fine) to sharpen that last tiny bit of steel to reach the edge when you reprofile it. The DMT XX coarse can take some big teeth out of the edge if you take it all the way to the edge, which leads to more time on other stones to remove those teeth and refine the edge. I was a little intimidated the first time I did a major reprofile (my Jess Horn), but I just said screw it and went for it. I am very happy with the results, and it has opened up a whole new world of knife performance for me.

Mike

[Harry White]

gunmike & thombrogan -- thanks so much for the detailed responses and pics. i'm going to go for it tonight, using an old "archangel" knife i keep in the garage to abuse. the steel is 440C on this knife -- it that "too hard" for a complete reprofiling? keep in mind this is a practice knife, so i'm not concerned with looks. thanks again.

i'll be sure to look up your threads on the other forum too.

here a pic of the beater.

[thombrogan]

440C too hard? My D8XX has seen my ZDP-189 D4, Catamount's ZDP-189 Jess Horn, loads of S30V from my personal collection and one of Gunmike1's S30V knives as well S7, 5160, 52100, 1084, VG10, AUS-8, 13C26, 440A, M2. 1095, and that 8C?CR stuff used in Byrd knives and it's pwnd them all. It's one of the few diamond hones where using light pressure is not recommended. You should be all set.

[gunmike1]

440C too hard? My D8XX has seen my ZDP-189 D4, Catamount's ZDP-189 Jess Horn, loads of S30V from my personal collection and one of Gunmike1's S30V knives as well S7, 5160, 52100, 1084, VG10, AUS-8, 13C26, 440A, M2. 1095, and that 8C?CR stuff used in Byrd knives and it's pwnd them all. It's one of the few diamond hones where using light pressure is not recommended. You should be all set.

Ditto, the D8XX makes mincemeat of ZDP 189 and S30V or any other steel I have put it to, and as Thom said use a lot of pressure. Most diamond stones are recommended for light pressure, but I have had no ill effects from using heavy pressure on my D8XX (which I tried from Thom's recommendations), and it cuts the reprofiling time dramatically compared to using light pressure and the stone shows no signs of losing it's cutting abilities. One thing to consider is that 440C (in theory) isn't the best steel for very acute edges, but I would still encourage you to go flat to the stone to thin it way out and then you can play with the microbevel at the very edge until you find an angle that gives good durability and performance. I usually run a 15 degree microbevel on my knives that are as thin as 4-6 per side.

Mike

[Harry White]

just what i wanted to hear! i know what i'm doing tonight -- putting my D8XX through a serious workout!

after the XX coarse diamond, i plan to follow-up with a combo 8" SiC stone (coarse, then fine), then go to a 6" medium arkansas stone, then finally a Hand America leather hone charged with chromium oxide.

i want to include the Sharpmaker between the arkansas stone and the strop, but after using four bench stones, i'm hesitant to swich gears with the SM rod setup. i may have to look into the Spydie benchstones for those last steps before stropping.

this place is great -- thanks again for all your help. :)

[gunmike1]

just what i wanted to hear! i know what i'm doing tonight -- putting my D8XX through a serious workout!

after the XX coarse diamond, i plan to follow-up with a combo 8" SiC stone (coarse, then fine), then go to a 6" medium arkansas stone, then finally a Hand America leather hone charged with chromium oxide.

i want to include the Sharpmaker between the arkansas stone and the strop, but after using four bench stones, i'm hesitant to swich gears with the SM rod setup. i may have to look into the Spydie benchstones for those last steps before stropping.

this place is great -- thanks again for all your help. :)

I usually go from DMT XX coarse to DMT fine to my microbevel with the Spyderco stones. I haven't had the greatest luck with stropping so I usually stop at that, but Thom Brogan was nice enough to give me a King 1000/6000 waterstone, so I will have to try the 6000 grit to see how I like the finish it leaves compared to the Spyderco Ultra Fine. I personally would recommend using the Spyderco Grits, though I'm not sure what grit your Arkansas stone is compared to the Spyderco stones.

Mike

[gunmike1]

For those interested, here is a link to a couple threads with some knives reground by Tom Krein (he can be reached at 479-736-3444):

http://www.bladeforums.com/forums/showthread.php?t=453772

http://www.bladeforums.com/forums/showthread.php?t=451515

My thread on regrinding my Native Flat to the Stone (before I had the D8XX):

http://www.bladeforums.com/forums/showthread.php?t=439904

My thread regrinding my ZDP Jess Horn flat to the stone:

http://www.bladeforums.com/forums/showthread.php?t=427611

This is where I learned that I REALLY needed better products for reprofiling. I was amazed that the Sharpmaker diamond hones did the job and retained all of their bite, but they just can't reprofile nearly as fast as the DMT D8XX. They are very good for smaller jobs, though.

Edit to add: My thread showing my new Caly Jr. ZDP reground by Tom Krein: http://www.bladeforums.com/forums/showthread.php?t=456767

Had to throw that in to show off my new baby!

Mike

[JaM]

What's the size and grit you guys reccommend on such a stone ? For replofiling a delica or endura sized knife for instance... ?

[thombrogan]

How much reprofiling are you doing? Changing the backbevel from 15 to 14 degrees? To 10 degrees? Grinding a new tip?