The low grit sharpening thread

[vivi]

I started carrying my Police 4 again yesterday. It's in my pocket tonight as well.

It was a little dull so I did a quick touch up using the brown rods at 20 degrees. About 15 strokes per side and it was shaving sharp.

I used to think this finish felt toothy. Running my nail along the edge it feels smooth and polished to me now. The edge on my Manix XL straight off the diamond rods feels completely different.

When I find some time I'm going to grind off the microbevel and give it a DMT X Coarse finish.

I'm excited to see how K390 works with an edge like that, considering how well it holds an edge for me at a higher polish.

[basedlarrydavid]

What exactly is wrong with smoothing out carbides? While I'm largely a coarse grit sharpener, the grit finish you want according to the task you plan on accomplishing while taking the hardness of the matrix into account should far supersede this in my opinion.

This has kinda been covered, but, there isn’t anything inherently wrong with smoothing out carbides. As I said, I try to bring out (what I think to be) the best characteristics of each steel I sharpen. And again, in my opinion, one of the most unique characteristics of Maxamet is that ~25% carbide volume and the hardness of the surrounding matrix, which gives said carbides strong support. So as I see it, smoothing them out too much by via a high polish sorta negates one of Maxamet’s best properties.

That statement was littered with references to my subjective preferences because I really don’t think there is one perfect way to sharpen any one steel. It’s all relative and based in the user’s, well, uses. That’s one of the reasons I generally ask sharpening customers questions about their usage and maintenance habits before performing the service. For instance, a dude sent me an S90V blade with which he uses to cut cardboard all day at his factory job. He wanted a super highly polished mirror edge. I said I’d be happy to do it, but a nice 40-20 micron edge stropped a bit would probably do a lot better.

I guess that’s a long way of saying that I agree with you, lol.

[Doeswhateveraspidercan]

What exactly is wrong with smoothing out carbides? While I'm largely a coarse grit sharpener, the grit finish you want according to the task you plan on accomplishing while taking the hardness of the matrix into account should far supersede this in my opinion.

This has kinda been covered, but, there isn’t anything inherently wrong with smoothing out carbides. As I said, I try to bring out (what I think to be) the best characteristics of each steel I sharpen. And again, in my opinion, one of the most unique characteristics of Maxamet is that ~25% carbide volume and the hardness of the surrounding matrix, which gives said carbides strong support. So as I see it, smoothing them out too much by via a high polish sorta negates one of Maxamet’s best properties.

That statement was littered with references to my subjective preferences because I really don’t think there is one perfect way to sharpen any one steel. It’s all relative and based in the user’s, well, uses. That’s one of the reasons I generally ask sharpening customers questions about their usage and maintenance habits before performing the service. For instance, a dude sent me an S90V blade with which he uses to cut cardboard all day at his factory job. He wanted a super highly polished mirror edge. I said I’d be happy to do it, but a nice 40-20 micron edge stropped a bit would probably do a lot better.

I guess that’s a long way of saying that I agree with you, lol.

Interesting. So what is your take on run of the mill-tasks lets take S90V for example. In a days use it will see cutting up boxes to make room in the trash bin, opening letters, opening blister packs, cutting plastic like on a paper towel roll, Cutting zip ties, Opening packages of meat and used with food prep to include vegetables and fruit even over ripe tomatoes also being able to laser through telephone paper with no snags and the desire is that it excel at all is S90V a pipe dream here or should we switch it up for a different steel?

If so then what degree of coarseness and or refined polished blade.

Near as I can tell polished blades and bevels are good for two things.

#1. YouTube idiots wanting to split hairs .... Literally... who get idiots like me to spend money on a wicked edge pro 3.

#2. people who are woodworkers which are not really in the Spyderco knife user-category to begin with as they use chisels, planes etc.... Perhaps there is the oddball that carves spoons etc with their pocket knife and well I actually wish I knew one to sit and practice withe He, He, He...

Curious to have this answered.. if anyone can that is. Gauntlet is thrown who has the chops to put up or shut Up Hmmmm?? :)

[Pelagic]

I appreciate the input addressing my question. I know carbide volume is a major factor in deciding what finish to use in sharpening. But most of us use knives for the same task over and over. We've found what edge finish works for our needs. If a coarse finish works best for me, I'll use a coarse finish on anything from 52100 to 15V. If I'm carving wood and want an extremely fine finish, I will use an extremely fine finish on anything from 52100 to 15V. I won't worry about smoothing out carbides. That's all I really meant. And to me, I feel like if a diamond abrasive is cutting extremely well, it should cut carbides in half (or cut a portion off) without dislodging the carbide from the surrounding matrix (beginning of tearout). I feel like pieces of carbide can help a lot with edge retention, not just full sized, untouched carbides. So that's why I was curious about people being concerned with "smoothing out carbides". Use whatever finish you want, keeping the properties of the blade in mind. While Maxamet will hold a coarse edge for a long time due to carbide volume and hardness, REX45 will hold a coarse edge for a fairly long time as well due to hardness and stability. Big difference in carbide volume between the 2 steels, but very little impact on what finish works best for a given task. Just my opinion.

[bbturbodad]

I like polished edges but today sharpened some Maxamet to a 150 grit finish off a Venev bonded diamond stone followed by 2 passes on bare basswood just to make sure I wasn't missing something. So far, for the things I usually cut, I still prefer a polished edge.




Probably won't be long before it looks like my PM2 again.

[Doeswhateveraspidercan]

Very nice indeed and great work truly something to present indeed.

Many will want to repeat your great result and in that spirit of cooperative learning I propose we do away with the inaccurate measurement called grit and use Microns instead as per the Grand Unified Grit Chart in order to simplify not only the buying process but further clarify what the heck we are talking about in the first place as grit measurements are so varied as to be terribly inconclusive from one provider to the next.

https://docs.google.com/spreadsheets/d/ ... o/htmlview

[bbturbodad]

The 150 grit Venev stone is marked 100/80 micron.

The polished edge on the PM2 went to 1200 3/2 which was proceeded by the 800 7/5 and 400 20/14 Venev stones. After the stones it was stropped on a 1 micron diamond lapping film then finished on kangaroo with .25 micron CBN spray from Ken Schwartz.

[Chumango]

Another take on the grit chart

https://www.gritomatic.com/pages/grit-chart

[RustyIron]

I like polished edges but today sharpened some Maxamet to a 150 grit finish off a Venev bonded diamond stone followed by 2 passes on bare basswood just to make sure I wasn't missing something. So far, for the things I usually cut, I still prefer a polished edge.

Thanks, bturbo.
I'm just becoming familiar with Maxamet. This afternoon I touched mine up a bit. It was still seriously sharp, but wasn't perfect, and I was feeling a bit OCD about it. The last couple times around, I've taken it down to 17° (minus the factory angle) and 0.25μ. I know how everyone says it should be coarse, but I'm really liking it with a high polish. Next week I have a couple new stones arriving that might change my mind.

[emanuel]

But what about Maxamet, REX 45, or a steel in between? What exactly is wrong with smoothing out some carbides on REX45?

Nothing bad in taking Rex 45 to a fine edge, at the end of the day it has the same low carbide volume as 52100 (5-6%) while being significantly harder, so it's edge strength will be improved. Nothing wrong with doing it with Maxamet too, since it's matrix is also high hardness so unless your arm is an an industrial cutting machine, it won't really make a difference for you except slicing less aggressively depending the medium you're cutting. I use Rex 45 mirror polished with a finishing of 1.5 micron diamond emulsion on strop, and my maxamet is still having the factory edge but I'll give it a polished edge when it will need a proper sharpening. For now, the 1.5 micron strop seems to keep it hair whittling sharp.

Looking at the edge under magnification on the Maxamet Manix, it seems to be 15dps low grit edge with a higher angle microbevel (possibly 20dps) that's mirror polished. I'm very satisfied with its performance so far, so I'll keep it polished.

I'm now curious about the next 15v knife in the works and how that one will perform with a polished edge, but that will also depend on what hardness spyderco aims for, but I'll most likely find a middle ground (1000 grit + 1.5 micron strop sound attractive looking at it's steel composition).

[The Meat man]

...Nothing bad in taking Rex 45 to a fine edge, at the end of the day it has the same low carbide volume as 52100 (5-6%)...

That's hard to believe!

[Evil D]

I started carrying my Police 4 again yesterday. It's in my pocket tonight as well.

It was a little dull so I did a quick touch up using the brown rods at 20 degrees. About 15 strokes per side and it was shaving sharp.

I used to think this finish felt toothy. Running my nail along the edge it feels smooth and polished to me now. The edge on my Manix XL straight off the diamond rods feels completely different.

When I find some time I'm going to grind off the microbevel and give it a DMT X Coarse finish.

I'm excited to see how K390 works with an edge like that, considering how well it holds an edge for me at a higher polish.

I think the brown rods are fairly high grit aren't they? I mean they're certainly not 300ish grit right? Some people still consider 1k to be low grit.

[Doeswhateveraspidercan]

Spyderco Diamond Rods = 40 Micron = 443.19 Grit

Spyderco Brown Rods = 15 Micron = 1252.881 Grit

Spyderco fine white rods = 6 Micron = 3307.740 Grit

Spyderco Ultra Fine White rods = 3 Micron = 6894.070

Yes The brown rods are actually quite refined and no where near coarse.

Micron sizes obtained from previously shared Grit chart.

Conversions calculated here: https://www.bestsharpeningstones.com/ar ... Calculator

[bbturbodad]

When cutting cardboard and paper with a low grit finish I need to wipe the blade off on my shirt every few cuts to keep the teeth from loading with fibers. Anyone else have issues with this?

[emanuel]

That's hard to believe!

Screenshot_2019-10-19-07-54-11.png

Well ok, so I just checked and came upon this. As per Larrin's article with experimental measurements of carbide volume for a typical HT for each steel, REX 45 is around 7 and a bit carbide volume, while 52100 is 6%. Another advantage that Rex 45 has over 52100 is harder carbides (Vanadium and Tungsten), while 52100 has just the unintentional and soft iron carbides. As of right now I have no knife in 52100 anymore, as Rex 45 does everything better than it in tasks that require toughness and a fine edge.

[Doeswhateveraspidercan]

Edited so people can read Larrin’s full article on their own.

Link on bottom.

Here is something to consider. Recently I think on a cliff stamp video the size of carbides was brought up and how one needs to use appropriate abrasives IE: Diamond which is harder than carbides like Vanadium, Niobium, Tungsten.

The size was said to matter because in order to get the best out of a high carbide steel blade the abrasives used needed to be smaller than the carbides otherwise the carbides were not being sharpened with the steel. If I recall correctly the carbides were being rounded.

Larrin seems to be saying something similar here: Borrowed from Larrin at knife steel nerds.com.

Powdered metallurgy steel is also described as a factor.

As usual a great read thanks for the continuing education Larrin.


Abrasives vs Carbides

Carbide size and hardness is also significant when it comes to grinding and sharpening knives. If the abrasive is softer than the carbide the abrasive is not able to abrade the carbide. Notably, aluminum oxide (Alumina), the most common abrasive, is softer than VC, NbC, and WC. However, if the abrasive size is larger than the carbide size then the abrasive is able to pull out the steel and the carbides together so that the carbide hardness isn’t as important. Abrasive wear tests of S90V and D2 showed superior wear resistance of D2 [7] even though the S90V has a large amount of hard vanadium carbide because D2 has very large carbides. This means that grindability of powder metallurgy steels is better than conventionally produced steels. So grinding and sharpening with coarse grits are generally effective with vanadium-alloyed powder metallurgy steels even if the abrasive is softer. At finer grits the hardness of the carbide becomes more important and polishing vanadium-containing steels can be challenging because aluminum oxide is too soft. Silicon carbide has a similar hardness to those hard carbides but is not clearly harder, and in general silicon carbide is not as good at cutting steel as aluminum oxide. CBN and diamond are significantly harder than any of the carbides so they are generally better at least in terms of grinding and polishing high wear resistance steels with hard carbides.

FULL ARTICLE:
https://knifesteelnerds.com/2019/07/15/ ... fe-steels/

[The Meat man]

That's hard to believe!

Screenshot_2019-10-19-07-54-11.png

Well ok, so I just checked and came upon this. As per Larrin's article with experimental measurements of carbide volume for a typical HT for each steel, REX 45 is around 7 and a bit carbide volume, while 52100 is 6%. Another advantage that Rex 45 has over 52100 is harder carbides (Vanadium and Tungsten), while 52100 has just the unintentional and soft iron carbides. As of right now I have no knife in 52100 anymore, as Rex 45 does everything better than it in tasks that require toughness and a fine edge.

I see. Thanks for the clarification! The carbide volumes are a lot closer than I thought.

[Bloke]

Curious to have this answered...

Hey Does, that’s a savage looking edge on the Military and it seems like you’re enjoying your new stones. I think it’ll be interesting to see how the thin edge holds up.

I like S90V and I’ve used it quite a bit, primarily in my Sprig which although not a fillet knife per se, does an excellent the job on fish I catch.

Anyhow, I don’t know the answer to your question but here’s a look at my coarsest finished blade.

This is my Southfork finished on a 220grit SiC stone and a half hearted strop with chrome oxide on stiff leather. No my sharpest knife but seriously aggressive.

This is as good a pic I could get of the edge.



Here’s another pic of the edge in a different light. :eek:



Push cuts hardwood surprisingly well. Grabs cigarette on contact and rough slices that too. :)

[vivi]

Strange stuff.

When I sharpen my S30V Manix XL on my diamond sharpmaker rods, I find it difficult to get acleanly shaving edge.

I tried out my BD1 Ronin 2 and managed to get it hair popping sharp off the diamond rods.

Not sure why the Ronin seems to get so much sharper off the same stones but it's a really nice feeling edge. Very toothy but push cuts through things pretty well.

I've been debating what sort of finish I'm going to give my VG10 Police 4. Might try out the diamond edge and see if it responds as well as BD1.

[emanuel]

I see. Thanks for the clarification! The carbide volumes are a lot closer than I thought.

Yes I was very surprised awhile back when I got schooled about it. I thought Rex 45 was somewhere close in carbide volume to Cruwear. I was totally wrong.