Experience with electro corundum stones?

[huntyukon]

Hello everyone,

does anyone here have any experience with electro corundum stones? How do they work when compared to Boride T2 or other AIO stones? Is there a noticeable difference?
Thanks.

 

[Mr.Wizard]

I have browsed dozens of abrasives catalogs and this is simply not a term that comes up often. I think it is merely another way to describe electric-arc-furnace alumina, i.e. Alundum, which doesn't tell you much. There are a number of types of alumina abrasive with some important performance differences. Which stones are you looking at?

 

[huntyukon]

PDT offer a set of electro corundum stones. They state they are supposed to be superior to regular ALOX like T2. Might be just marketing. I just recently ordered some SIC up to F400 and T2 up to F1200. That will have to suffice for now. Considering all the stuff I bought in the last couple weeks, I think I spent enough mulla for a while

Thanks for the reply, Paul

 

[Mr.Wizard]

huntyukon I have searched the PDT catalog and I do not see this product. Could you please point me to it?

 

[huntyukon]

Sorry about the late replies lately. Was travelling and just arrived in Germany last night.

I’m not certain if I’m allowed to post a link, but I’ll send it to you. You can also find it on their website abrasivetools.eu
and click on “sharpening accessories”. The stones will be at the bottom of that page.

I was told that is PDT’s website. Even though it doesn’t say Poltova or PDT in their domain

 

[huntyukon]

Definitely enjoying your chart btw.
It’s pretty neat. I can see how that took a lot of time and effort to make.

Oh, have you ever used water based compound or suspension/emulsions on non stainless steel? I’m Just curious if it would be an issue, as long as one wipes the blade down with alcohol and the rub some oil on it?

 

[Mr.Wizard]

Sorry about the late replies lately. Was travelling and just arrived in Germany last night.

I’m not certain if I’m allowed to post a link, but I’ll send it to you. You can also find it on their website abrasivetools.eu
and click on “sharpening accessories”. The stones will be at the bottom of that page.

I was told that is PDT’s website. Even though it doesn’t say Poltova or PDT in their domain

No worries. You reply whenever it's convenient and you're in the mood to do so.

I see them now. I was confused because I was looking at //pdt.tools/ and I don't see those products there.

The description is interesting. I would suppose these use white fused alumina which is distinguished from sintered alumina, e.g.

Fused minerals see multiple benefits compared to those produced through other processes, such as sintering. Before a sintering process can even begin, the materials need to be sized very carefully in order to ensure the desired reaction. The electric arc furnace does not require such precisely sized materials, however, saving both time and energy—and the resulting costs.

A sintered material also typically has much more porosity than a fused mineral, due to the lower temperatures involved in the sintering process. Since materials in the fusion process are in their liquid state, porosity is reduced dramatically. In fact, the bulk specific gravity of a fused mineral is very close to its theoretical specific gravity, which is not the case with a sintered material.

Purity is another impressive benefit of the electric arc furnace technology. As mentioned previously, the fusion process results in a virtual 100% conversion of the minerals. If we look back at our example of mullite, the same alumina and silica processed through sintering would not be able to achieve the electric arc furnace’s 100% mullite end product. In addition, a small percentage of unreacted alumina and silica would remain following sintering, creating waste and process inefficiencies.

But then it says "sintered electrocorundum." These could be solid sintered blocks like the Spyderco, Idahone, and Norton Ascent stones except that it says "ceramic bond" and frankly the grits given wouldn't make sense. I shall have to do some reading to try to understand this.

 

[huntyukon]

No worries. You reply whenever it's convenient and you're in the mood to do so.

I see them now. I was confused because I was looking at //pdt.tools/ and I don't see those products there.

The description is interesting. I would suppose these use white fused alumina which is distinguished from sintered alumina, e.g.



But then it says "sintered electrocorundum." These could be solid sintered blocks like the Spyderco, Idahone, and Norton Ascent stones except that it says "ceramic bond" and frankly the grits given wouldn't make sense. I shall have to do some reading to try to understand this.

Very interesting reading. If it’s true what PDT states they may work better than some other alumina alternatives, but I heard somewhere, from a guy that used those, that might not be the case. Best way to find out is I order them, eventually. Price is similar to Boride T2 and those perform quite well on my carbon steels. That’ll have to wait though. I bought a bunch of sharpening stones and gear lately

On another note I just got me an Endura in K390 from a friend. Man, that steel seems to hold and edge well. Definitely a noticeable difference to my M390 blades.

The offer to that CBN Paste stands btw. Thank you for checking out those stones. You sure know your stuff, Paul!

 

[Mr.Wizard]

huntyukon I spent some time this morning searching for an alumina production method that uses both electric furnace and sintering but it was difficult because these are so often juxtaposed as above. I was starting to think this was a translation error when I came across one that would explain it. How likely this is I don't know, as it seems to be an expensive and specialized process that has since been replaced by other methods, and it is described in the context of biomechanical implants rather than abrasives. I'll copy the relevant section below. I haven't delved into production methods this deeply before so pardon my naiveté if this turns out to be a common process.

Please let me know if the CS-HD stones work on K390 or if diamond is necessary, and if CS-HD works at some levels but not others, e.g. roughing or finishing. I haven't had the chance to work on such steel myself.

Since this is the second time you have offered the cBN samples I see that it was not merely a polite gesture. I accept your generosity again; I'll email my shipping address.

 

[Mr.Wizard]

Oh, have you ever used water based compound or suspension/emulsions on non stainless steel? I’m Just curious if it would be an issue, as long as one wipes the blade down with alcohol and the rub some oil on it?

I forgot to reply to this. Several of my diamond compounds are universal-base, meaning oil/water/alcohol soluble, and I have a 0.25µ diamond spray (suspension) that I believe is water based. However I don't use any of these wet so I don't think this applies to your question.

I do almost all my sharpening with water and with very reactive carbon steel I will get surface rust, but not in the area that is being worked (the bevel) as it doesn't sit wet long enough to be an issue. I cannot recall seeing it appear on areas that have been stropped with that universal-base diamond on leather, but then again I cannot think of where I would have given it the chance. My own pocket knives are all stainless or semi-stainless, and when I sharpen kitchen knives or any knives for others I typically do a final wipe-down with isopropanol for sanitation and to remove any Sharpie remnants. On the very reactive steel I would then polish off the surface rust and do a wipe-down with board butter—a mix of USP mineral oil and bee's wax.

 

[huntyukon]

I spent some time this morning searching for an alumina production method that uses both electric furnace and sintering but it was difficult because these are so often juxtaposed as above

Thank’s a bunch. As always, your answers are super helpful and oftentimes even adress things I never would’ve thought of.

Please let me know if the CS-HD stones work on K390 or if diamond is necessary, and if CS-HD works at some levels but not others, e.g. roughing or finishing

I will absolutely do that. As soon as I’m out of the hospital again, I will try them on my k390. I’m curious to find out how they’ll work on it. Also compared to my CBN stones.

Since this is the second time you have offered the cBN samples I see that it was not merely a polite gesture. I accept your generosity again; I'll email my shipping address.

I absolutely meant it and have replied to your mail.

do almost all my sharpening with water and with very reactive carbon steel I will get surface rust, but not in the area that is being worked (the bevel) as it doesn't sit wet long enough to be an issue. I cannot recall seeing it appear on areas that have been stropped with that universal-base diamond on leather

That’s very interesting. I’m not worried to use water based products on carbon steel then. I’ve been getting quite interested in some of the carbon steels out there. There are a few pastes that I’d like to try on some of my kitchen knives, but wasn’t sure I should do that with pastes that have some water content.

On the very reactive steel I would then polish off the surface rust and do a wipe-down with board butter—a mix of USP mineral oil and bee's wax.

That’s a great idea!

Thanks a bunch for your help with this, once again. I greatly appreciate it. You truly are a wizard . Have a great weekend