Native flat to the stone & pushcuting newsprint vs. yellow pages observations

[Dog of War]

This is actually a really simple geometry issue, take the three apex points of a isosceles triangle. When connected by straight lines they enclose an given area, when connected by convex lines they enclose a greater area which has no maximum, when enclosed by concave lines they enclose a smaller area which has no minimum. Of course either of the curved geometries can be approximated by multiple straight lines with the differences between them going to zero as the number of lines increases, but there is no practical difference in general with even 2-3 straight lines.

This implies that the use of such geometries should be fairly straight forward. The reason that it is not is because in general north american knives are vastly overbuilt for what they are designed to do and when they are modified to remove steel, by whichever way the user decides, this curvature gets associated with the change in performance. This is really silly and you don't see it elsewhere....

As you've emphasized many times, cross section is what matters, and once you recognize this it becomes very straight-forward.

I noticed hardheart and AG Russell discussing thin blades in that seemingly perpetual 13C26 thread on the general forum, I suspect the overuse and misuse of thick stock and overbuilt blades has contributed to the myths surrounding convex grinds and edges: so many blades are so far from optimal, any relief added improves performance. As Russell points out few seem to be interested in thin blades .... that says a lot IMO about how widespread this kind of misunderstanding really is.

A productive discussion of the grinds centers on one question - what is the force responce of the material to being cut.

Absolutely. And even if you decide to run an edge or profile more obtusely due to other uses a knife may see, IMO it's almost a necessary step in evaluating a knife to reprofile to the point where any weakness - rolling, chipping, carbide pull-out, etc. - begins to show. In the end the objective is to choose an edge and profile that cuts with the least required force for the durability and toughness required by the work to be done.

That sounds like knife design by Mr. Miagi.

If you gave Mr. Miagi a tactical folder I think all he would find it suitable for is digging in the garden.

 

[Cliff Stamp]

I suspect the overuse and misuse of thick stock and overbuilt blades has contributed to the myths surrounding convex grinds and edges: so many blades are so far from optimal, any relief added improves performance.

Yes, what is unfortunate further is that this is spread as the actual way it should be fixed. This is a bandaid solution. A knife should not need a relief grind, that is what the primary grind is supposed to do. Of course if you can't fix the primary grind then you use a relief grind.

In the end the objective is to choose an edge and profile that cuts with the least required force for the durability and toughness required by the work to be done.

Exactly right, the main problem comes from over use of steels which are never meant for the type of knives they are used for which predicates geometries which are silly and you end up with folders which have edges which are thicker and more obtuse than a felling axe.

If you gave Mr. Miagi a tactical folder I think all he would find it suitable for is digging in the garden.

Digging is abusive to knives, even knives which have edges which are thicker than spades. I don't quite understand the science of that, I think it must be similar to the cartoon laws of physics. I should compile a list of forum laws of knife performance.

-Cliff

 

[gunmike1]

Are you suggesting that flat grinds are thinner than convex grinds? I did that once and it turned into a multi post argument. Don't think I want to comment anymore than that on it.

As said by Dog of War "This is called The Zen of Convex and Flat: Take a flat grind and convex it without changing the apex, the convex grind will be thinner. Then flatten it out, you have an even thinner flat grind. Go thinner and thinner, convex becomes flat when all metal is gone - and instead of ultimate performance, you now have none."
As the primary grind got flatter and I was abrading more material, it gets more and more tempting to convex the bevel to reach the edge with your new grind. That is why I said flatter was thinner, because it seems to me that going flat to the stone all the way until you reach the edge gets it the thinnest initially, then DOW's quote goes into effect.

Are you suggesting that convex grinds hide uneven grinds? Not sure I agree but, if so cool another reason to like the convex grind.

In the case of how I was thinning out my knife, if I had stopped at a certain point and started convexing the bevel right then the grind would have looked more even. Of course, if I had done that, then I would have to grind flat to thin it out more, and then convex it, and then flat grind it, and then.....

Yup, the larger the bevel is to grind the longer it can take. I tend to press harder and go faster and get sloppier witch all can produce some unevenness to the grind of the blade. Just like grinding more on one side. I don’t mean to suggest that is what you’ve done and that is why your blades look like the factory grind was uneven. However, it is possible to unevenly grind a blade by hand as you have also said even with using the blade itself as a jig flat to the stone.

Well, the factory using power equipment, which grinds infinately faster than me and my poor little hands on a benchstone, on a mass production line trying to get as many knives out as possible, though still with quality in mind, makes me lean towards the factory grinding the primaries uneven. I already gave examples of high quality knives that I have where you could visually see the uneven primary grinds straight out of the box gives me the confidence to say that a lot of knives come out of the factory with uneven grinds. It doesn't bother me, as long as it cuts good and the lockup is good I'm happy. I'm glad for you that your knives have all been ground close to perfectly from the factory, lets just agree to disagree on this one.

 

[gunmike1]

As a follow up to my yellow pages observations, see below and see my review of my new Manix in the review forum for it's performance.

I have a new utility razor at work here and benchmarked the performance and came up almost identical to my other results with a razor, with an average of 2.94" with all between 2.75" and 3.1" on the yellow pages. I don't have my newsprint here to test it. This is similar to the results I got from a no name, years old razor that was in my toolbox, as posted in my Manix thread. It is very sharp, and with the almost non existant cross section you can see why razors cut so well.

I sharpened the Mod U2 Cliff lent me on the 600 DMT, pretty flat to the stone to remove the shoulders of the 15 degree microbevel, and sharpened it at around 10 degrees per side (guesstimate, I did it freehand), and was amazed to find that I got an average of 3.39" on the yellow pages, with all results between 3.19" and 3.75" (tested here at work on the same yellow pages as the utility razor). Before, when I did my first cut at over 2.5", the knife had been sharpened to a high polish on a 15 degree microbevel and used some since the sharpening. I am pretty amazed at the performance, maybe I got lucky on that sharpening, but it is extremely easy to get a burr free edge at that finish on that knife. Maybe the 10 degree microbevel makes a huge difference in sharpness compared to the 15 degree microbevel, or I am slightly rolling the edge while stropping? Either way I am real happy with those sharpness numbers. I definately have to check it's durability at that angle, if it doesn't chip out it should cut cardboard for a very long time at that finish. I have been testing my new Manix full time, so when I use the U2 more I will try the same sharpening methods and try to average it out to see what the sharpness results level out at.

Also, since it is Christmas time and I have been working my butt off (have to pay for all of those presents, and new tires on my car), I haven't done anything with the Native either, but I promise to report back when I get off my butt to test it. The Manix is my new toy, and I am testing it on everything since I got it on my birthday (12/15) to check for chipping and performance, in the next few days and weeks I will get back to testing my other knives.

 

[Cliff Stamp]

That is fairly impressive as most people judge those razors are very sharp, hence the name obviously. However in terms of ultimate sharpness, they are not actually very high as they often have burred edges as shown by Lee. It is the case that any measure of sharpness which is a cutting test will be influenced by angle, though generally not significantly when the medium is so slight.

-Cliff

 

[gunmike1]

That is fairly impressive as most people judge those razors are very sharp, hence the name obviously. However in terms of ultimate sharpness, they are not actually very high as they often have burred edges as shown by Lee. It is the case that any measure of sharpness which is a cutting test will be influenced by angle, though generally not significantly when the medium is so slight.

-Cliff

How right you are about razor blades and burrs. I just checked the one I ran against the U2 and on one side you see dark, on the other a large, bright, burr under a 10X loupe. I will retest with the next blade in the handle, and see if it is similarly afflicted. I cut a massive amount of cardboard into tiny strips with the U2, to the point where it was only scrape shaving. I hit it several times flat to the stone, as there was some chipping near the choil, and then hit it with several passes around 12 or so degrees per side on the 600 DMT to get a nice edge. I did a quick check on the yellow pages and the cut was well over 3" from the point of hold based on putting the knife next to the paper for comparison.

Tommorow I will try to do a proper test of the U2 against the next razor in the handle and see how the averages look. If the razor has an ugly burr like the first one I'm guessing the results will be similar. Maybe I should de-burr one of the razors and see how good it performs with a clean edge. I'm trying to think of the best way to do that and not cut the crap out of myself, and what hone to start with and work up to.

 

[Cliff Stamp]

If you can, look for Olfa blades, they are the sharpest utility blades I have seen. They have two types, standard and ultra-sharp.

-Cliff

 

[gunmike1]

If you can, look for Olfa blades, they are the sharpest utility blades I have seen. They have two types, standard and ultra-sharp.

-Cliff

I will look for them. The main thing I see around here is stanley. I will hunt online and see what I can find. I would like to try the ultra sharps, those should be impressive.

 

[gunmike1]

Well, I have good news and bad news on the Native reprofiling project. All of the news with the knife is good, so lets start with that.

I applied a 15 degree microbevel with a 600 DMT, then worked my way from the medium to the ultrafine Spyderco benchstones. I was very impressed, it sharpened up with no deburring necessary. I only have my 10X loupe to check for burrs, as I have lost my radioshack lighted scope, but it shaved evenly and had no burr under 10X. The edge formed very clean, with no chipping or crumbling. Again, I would have preferred to look at it with my scope, but you make due with what you have.

On the Yellow Pages it averaged 2.24" from the point of hold on push cuts, with all results between 1.92" and 2.50". Not as good as the U2 or a razor blade, but much better than my out of the box Manix (1.34"). The factory edge on this Native could only pushcut newsprint about 1.5" from the point of hold, so this is a vast improvement.

Now to the bad, or should I say stupid, dangerous, and dumb. I suffered from a rectal/cranial inversion when I opened my 6 pack of M-tech knives that I got for Christmas. Instead of holding the package in my left hand and cutting straight through, away from my body with my right, I held the package between my left arm and my body, tucked under my armpit and proceeded to cut. A really funny thing happened, as the now extremely sharp knife flew through the thick plastic with about zero resistance, and it also flew through the middle of my thumb and forefinger, which were about 6" away from the end of the package and piched together (too used to holding up media for testing pushcutting?), with no effort either. The cut through the thumb went straight through, about 1/2" up the thumbnail, cleanly slicing through the meat of the tip to a gaping wound. Similar but less lengthy cut on the forefinger meat and nail. Both cuts were extremely clean, in fact the ER people were incredulous when I told them a pocket knife made the cuts. I quickly wrapped my hand with a dishrag, tried to soak up the blood, and grabbed my first aid kit. I cleaned the wounds, put gauze on them, and wrapped them extremely tight in gauze wrap.

That worked great until the medical staff took it off to take a look. Bottom line, the cuts were so clean they only needed to suture the skin, they left the thumbnails split and open, and x rays confirmed I didn't nick a bone. Again, the nurse (a guy) was really impressed a pocket knife could cut so deep so cleanly, and said it may have been worse if the cuts weren't so clean.

The bottom line, though, is that I am lucky. It easily could have been two of my fingertips flying across the room! Or I could have slit my wrist to the bone. PAY ATTENTION AT ALL TIMES WHEN YOU ARE USING SHARP TOOLS! Luckily I just have to put up with a little discomfort and lecturing, but I had my head up my butt for only a split second and did a lot of damage to myself. I now have a throbbing reminder and a good mental picture in my head to remind me to pay attention at all times.

Oh yeah, the knife didn't chip! I guess we can add that to the good column. Now I need to test it on cardboard and see how it holds up.

In the bad column is that on 4 of the 6 M-tech knives the liner lock doesn't even engage the tang. One locks up solid, and the other that locks up has such a weak liner that you can close the blade to 45 degrees with it engaged. What do you expect from a 6 pack of cheap knives, though. I need to sh*tcan them out of spite. If I would have cracked open a 6 pack of beer my life would be a little better now, but live and learn.

 

[Cliff Stamp]

I suffered from a rectal/cranial inversion when I opened my 6 pack of M-tech knives that I got for Christmas.

I can go one better. A few years back I was limbing some trees and for the small ones I manipulate with my left hand and trim with my right. Well my attention wandered and I swept the knife from behind my hand down the tree and nearly cut into all four fingers of my hand, splitting them directly parallel. Surprisingly, not one bone was cut and a few stitches on each finger later and no worries, with only some minor sensation loss in my index finger.

Idiotic behavior aside, it is interesting to see the S30V blade behind, this would be expect given composition/hardness, once the geometrical influence is normalized I would expect however for the performance to be closer together.

-Cliff

 

[gunmike1]

I can go one better. A few years back I was limbing some trees and for the small ones I manipulate with my left hand and trim with my right. Well my attention wandered and I swept the knife from behind my hand down the tree and nearly cut into all four fingers of my hand, splitting them directly parallel. Surprisingly, not one bone was cut and a few stitches on each finger later and no worries, with only some minor sensation loss in my index finger.

Idiotic behavior aside, it is interesting to see the S30V blade behind, this would be expect given composition/hardness, once the geometrical influence is normalized I would expect however for the performance to be closer together.

-Cliff

Yeah, the Native is still quite thick compared to the U2. The stock is much thicker, and the edge is much thicker and more obtuse. Of course that is independent of sharpness, but for me the thinner the grind the sharper I can get it. If it holds up well on cardboard I think I will send it with the ZDP Horn to be thinned out by Krein. Plus, without my 100X lighted scope I don't doubt my edge was slightly burred. I will buy a new scope tonight and check it out.

I'm glad to see you came out of your episode rather unscathed. My fingers don't even hurt that bad, another byproduct of such a clean cut I guess. The only part that really had much pain was the shots of lidocaine so they could do the stitching. The shots in the thumb I didn't even twitch, tough guy that I am! Now the shots in the forefinger, I made all sorts of amusing faces when they did those ones. No screaming, though, so at least I can keep some level of pride.

 

[Cliff Stamp]

That's easy to fix, don't get the shots.

-Cliff

 

[gunmike1]

That's easy to fix, don't get the shots.

-Cliff

Of couse, the pain of the shot intially I'm assuming helped me overall, as I felt NOTHING when the large hook was passed through my fingers by the seamstress, err, Doctor. Of course, this is all speculation on my part, as I have only sliced my fingers in half before, never meathooked them.

 

[gunmike1]

I took pictures when I changed my bandaged fingers, I will try to post them later. I may as well post the pictures of the Native, as well, you can still see the line of blood where the knife went through the fingers at the deepest point. I guess should have borrowed a dremel tool to put a Dork Ops style blood groove in the blade, but I'm not sure if it would work on my bodily fluids as I'm not an Al Quaida in needing of covert deanimation, at least I don't think so. I was surprised that the thumb injury went all the way through almost the total length of my thumbnail, I didn't remember it going that far up the thumb, and the pointer finger is still seeping a little blood through the open finger nail wound. I'm not sure if the total length of the thumbnail cut will show up on the pics, as that was the first finger cut, thus the cleanest cut and it isn't seeping blood through the nail.

 

[gunmike1]

Sorry, no pics uploaded yet, but I got another 100X lighted scope and was appalled at my sharpening job on the Native. Definately a burr there, just not easily seen under bad lighting with a loupe. It is small enough where it shaves evenly on both sides and is still pretty sharp, and it didn't break off when I cut throuth the package and my fingers, but it is there. I tried deburring and sharpening again, but my unintended surgical procedure has screwed up my sharpening abilities, as I use both hands to sharpen. Once I get a good, clean edge on the Native I will retest it and I am expecting much better results. When my XX coarse DMT comes in I may thin it out even more, as reprofiling is still doable, as it doesn't require precision. Hopefully by the time they take the stitches out next week my fingers will feel good enough to do a good job sharpening. I sharpen with both hands, and even when I just use my left hand for support it bothers me (like holding the benchstone against the sharpmaker rod for angle control, my training wheels). Forget about it when I use my left hand for a precise sharpening stroke. Also, I do all of my precise benchstone work lefthanded (when I don't use my training wheels), and the throbbing and E.T. like fingertip bandages just screw me up.

 

[gunmike1]

Now, for the pain. If you are squeamish, tough, it's too late! Really though, they aren't that bad. The stitches come out tomorrow. The thumb was hit first, and it is hard to tell but it cut lengthwise almost all the way through to the top of my nail, and sliced my finger tip in two right through the meat like it wasn't there. Very clean cut. Very tightly wrapped gauze bandages and sutures healed that. The other finger is self explanitory, again split through the nail and the meat, just lucky that I didn't hit bone, or just go through at a different angle and launch my fingertips across the room. This one wasn't as clean of a cut as the Native had already gone through a package and my thumb, so it was losing steam by this point. As it was, they were gaping, gushing, offset wounds that were pretty ugly until you used a lot of pressure with the gauze wraps to line them up right, and then sewed them in place. Repeat after me; "No being a dumbass with very sharp knives".

 

[gunmike1]

I sharpened the Native flat to the stone to remove my fingers from the steel, then put a 15 degree microbevel on it with my DMT 600 then went to the Spyderco Medium. Using my lighted scope to make sure there were no burrs, I got better results this time.

My results with the yellow pages at the Spyderco Medium finish are:

2.64" ave. from the point of hold, worst cut was 2.5", best cut was 2.81"

I will go to Spyderco fine, note the results, then continue to the ultrafine and note the results again. I may or may not strop it after that. If I do strop it I will follow Thom Brogan's advice to put a couple drops of Diamond paste on copier paper and use a glass backing. Thom Brogan sharpened a couple knives for me and uses that technique, and I am very impressed with his results. Stropping seems to be hit or miss with me, I think mainly due to edge rolling from using too much pressure in the leather. I am interested in if the edge continues to take a finer polish at 15 degrees, or if it will get to a point where the edge starts to degrade when I go to finer abrasives. We will see. I think my results were better this time mainly due to having a very clean edge, instead of the slight burring I had before. Hopefully I will have time to refine the edge in the next couple days and I will report back with the results each step of the way.

Mike

 

[thombrogan]

Hiya, Mike!

To clarify, one of the knives you got back had been stropped in that manner to remove burr-stuff, but you done had to mention Ben Dale so both edges got redone ending with 0.3 micron aluminum oxide polishing film on an EdgePro tape blank.

 

[gunmike1]

Hiya, Mike!

To clarify, one of the knives you got back had been stropped in that manner to remove burr-stuff, but you done had to mention Ben Dale so both edges got redone ending with 0.3 micron aluminum oxide polishing film on an EdgePro tape blank.

Well, I'm glad I mentioned Ben Dale, because you got them edges damn sharp! At least as sharp as Ben got my R2. I can get my really thin edges that sharp, but I haven't been able to get my thicker edges (like the one's you and Ben sharpened) to that level yet, and I may never get them that sharp. I guess the really thin and acute edges just make shapening that much easier that even a dope like me can get good sharpness with them. I know that in principle sharpness is independent of angle, but with me the thinner and more acute the easier it is to get really sharp. I still need practice on the thicker ones, I guess. I think it is because on the thin edges I am just working less steel, so less burring comes from my not so coordinated hands, thus better sharpness. Whatever the case, you definately have some skills, Thom. If you could have mailed them back to me with the knives it would have been nice!

Mike

 

[gunmike1]

Just for reference, here are Thom's results on my Manix and Byrd Cara Cara. He reprofiled both to about 10 degrees per side, and then brought them up to these levels of sharpness on the yellow pages:

Manix: 2.73" ave, worst cut 2.63", best cut 2.88"

Cara Cara: 2.47" ave, worst cut 2.25", best cut 2.75"

Both very sharp, MUCH sharper than my factory Manix, and pretty close to a utility razor blade. Pretty damn good for such relatively thick edges compared to what I am honing.

Thom, you da man! You know, most people charge a lot of money to sharpen people's knives to levels like that. In fact, I bet most people who sharpen for a living can't match you. Career change time? Nah, it's more fun as a hobby and not your real work, huh?

Mike