Stropping S90V

[WorkingEdge]

Hello Everyone,

So I have been using chromium oxide on the back of leather for stropping to maintain edges. Good results with most steels but could not get S90V to tree topping sharpness (works for me on ZDP, superblue, m390 / cts204p, Cruwear). Also difficulty with K390 and of course S110v (forum native, not Mule as that is due in today!)

Out of frustration, I had some 0.25 micron diamond spray and sprayed onto the chromium oxide loaded strop and went at it again with my S90V and my goodness what a difference!

Anybody with similar experience with chromium oxide having difficulty with high carbide steels?

More interestingly is what effect does having the diamonds mixed with chromium oxide do??

[Cliff Stamp]

The diamonds are more abrasive, the edge simply wasn't close enough to sharp for the chromium oxide based abrasive to cut enough of the steel. It wasn't s90V specifically, just the state of the edge.

[WorkingEdge]

The diamonds are supposedly 0.25 microns with the chromium oxide listed as 0.5 microns but who knows how accurate that is.
On a previous thread, this is the knife I mentioned before as being sharpened at 15 dps to 30k (0.5 microns) with Shapton. It split hairs until I started using it and was stropping to try and maintain. I figured the chromium oxide was just insufficient for this kind of steel?
I try not to over strop as I have read your other threads as well.

[Cliff Stamp]

The stropping compounds are rarely precisely rated. Chromium oxide will cut that steel, it will cut any steel, but you have to have an edge very sharp before it. As the carbide level goes up this becomes even more important as the cutting slows down. Diamonds however cut all steels the same, as all steels are very soft in comparison.

[WorkingEdge]

Thanks Cliff. Perhaps too aggressive with angle and finish for this steel to try and maintain high sharpness.
To improve stability, I've thought about making convex edge with edgepro (by bending the rod) starting at 15dps at the top of the edge with 20dps at the apex. Is it worth the effort or better off V bevel at 20 dps?

[Cliff Stamp]

The problem with a lot of these terms, and the reason for the conflicts is lack of definition of the terms. If I was to say for example that 15 dps is too low to hold a high sharpness what would you interpret it to mean, some people would think it means it can't hold a face shaving edge, some might think scrape some hair from your arm, some might think slice a piece of cardboard. S90V is in the category of ultra-low edge stability steels which means it needs angles of 20-30 dps to have the same stability that AEB-L does at 8-12 dps. How much you notice this will depend on your tolerance for sharpness.

In regards to curvature, I would doubt you would be able to see a difference in use in cutting ability or edge durability in regards to a 20 dps micro-bevel which was flat or convex.

[JNewell]

S90V is in the category of ultra-low edge stability steels which means it needs angles of 20-30 dps to have the same stability that AEB-L does at 8-12 dps. How much you notice this will depend on your tolerance for sharpness.

Qs:

1. Why - what attributes of the steel formulation lead to ultra-low edge stability?

2. What other steels are in that group? Was S60V (440V)? I assume S30V is not in that group?

[WorkingEdge]

And more questions:

Would making the entire edge convex improve stability to any appreciable extent (as opposed to just a microbevel)?
What I tried to articulate above was to have the edge start at 15dps to keep it from being too thick but convexing to 20dps at the apex.
My guess is that it would still not make much of a difference?

JNewell - you have been here much longer than me and I have learned much from your posts. As to question 1, I will nonetheless venture to say it is due to carbide volume (assuming everything else being equal). Let's see if I have learned anything when Cliff answers! :)

[Cliff Stamp]

Qs:

1. Why - what attributes of the steel formulation lead to ultra-low edge stability?

The high carbide volume.

In reference to the published work of Landes :

"He classifed steels into three groups, type I, type II, and type III mainly based on carbide volume, 0.5-5%, 5-15%, and greater than 15% respectively. These groups needed different angles to both take and hold a high polished sharpness, 8-12, 12-20, and 20-30 degrees per side respectively. The greater the size and volume of carbide, the greater the angle required to keep the edge stable."

These are based on direct measurements of the strength of the actual edge under compression. Even though 10V for example would have a very high compression strength when the sample size is large, the compression strength is low when the sample size is small (the apex is on the order of a micron thick) as the steel fractures around and through the carbides.

2. What other steels are in that group? Was S60V (440V)? I assume S30V is not in that group?

S30V is near the top of type II.

Carbide volume levels are one of the easier statistics to find as most people publish them as they are strongly promoted as they are what produces wear resistance.

What I tried to articulate above was to have the edge start at 15dps to keep it from being too thick but convexing to 20dps at the apex.
My guess is that it would still not make much of a difference?

It depends on what you are doing with the knife, if you are not chopping into anything then even 10 dps is a very heavy edge. The edge will be stable (again not chopping/prying) if it was 10 dps and then in the last < 0.005" was 20+ dps.

To clarify if you are cutting into metals and such then you might want to bring the 20+ dps part up to at least 0.010" but if it is just cardboard, ropes, etc. there is no need.

I normally set the edges on what I consider light use (no chopping, or heavy metal cutting) to 4-8 dps (depending on knife/steel) and then apex at a true-micro. The only downside to this is that you have to be prepared to see visible damage if you hit an inclusion.

This is why I suggested 0.010"/10 dps : 20 dps micro. That bevel is very strong, you could cut up cardboard boxes and hit a staple with no real concern. If I did that on the bevels I normally run which are :

0.001"/5 dps:<15 dps micro, you would likely see damage on the order of 1/2 mm deep. But for me that happens so rare I am not going to sharpen a knife all the way around that.

Plus I usually keep at least one knife which does the bulk of the hard non-cutting work, including dirty materials which has heavier edge similar to the one I noted in the above.

Of course if the steel has a very high edge stability there is no need for the heavy micro-bevel.

[Ankerson]

Hello Everyone,

So I have been using chromium oxide on the back of leather for stropping to maintain edges. Good results with most steels but could not get S90V to tree topping sharpness (works for me on ZDP, superblue, m390 / cts204p, Cruwear). Also difficulty with K390 and of course S110v (forum native, not Mule as that is due in today!)

Out of frustration, I had some 0.25 micron diamond spray and sprayed onto the chromium oxide loaded strop and went at it again with my S90V and my goodness what a difference!

Anybody with similar experience with chromium oxide having difficulty with high carbide steels?

More interestingly is what effect does having the diamonds mixed with chromium oxide do??

I use Silicon Carbide to strop with usually, steel doesn't matter. :)

But then I touch up on a ceramic rod most of the time then if i want to strop it to refine the edge even more it would be Silicon carbide on a leather strop, smooth side.

One can however use Chromium Oxide if the edge isn't too dull.

Strop I use.

[WorkingEdge]

Hi Jim,

I recall in a previous thread you mentioned using the slurry from the MoldMaster stones (forget the grit stone it was coming from though). Do you use the same slurry even after you have otherwise polished your bevel up to 6000grit tape? By the numbers it would seem like go to a lower grit but then I'm sure leather is causing a different effect on "grit size" as well.
I could buy one of those stones and pulverize it to make a slurry. :)

[Ankerson]

Hi Jim,

I recall in a previous thread you mentioned using the slurry from the MoldMaster stones (forget the grit stone it was coming from though). Do you use the same slurry even after you have otherwise polished your bevel up to 6000grit tape? By the numbers it would seem like go to a lower grit but then I'm sure leather is causing a different effect on "grit size" as well.
I could buy one of those stones and pulverize it to make a slurry. :)

Slurry from the Norton Medium SIC stone.

I don't polish the edges on my users.

[WorkingEdge]

thanks for clarifying.

Slurry from the Norton Medium SIC stone.

I don't polish the edges on my users.

[free2game]

I've had pretty good luck doing a couple of backwards swipes on 3m trizact sandpaper then switching to a chromium oxide loaded belt. Not with S90V, but it works great on D2, S30V, and CPM 154 with very quick results.