Recommendation? What are the different types of abrasive materials?

[Bo-dacious]

What are the different types of materials used in sharpening. For example aluminum oxide or silicone carbide. What are these, what are they best for and where can I find them. Like in a natural stone or something for example. Also, what are the common sharpeners made of like natural stones, synthetic stones, stropping Compounds, abrasive belts for the work sharp for examples. Also, I bought some Dremel grinding stones a while ago. They said for grinding metal. They were made of Red Corundum. Is Red Corundum for stainless or carbon steel? Or for steel at all?

Thanks for the help,

Bo

 

[PeterS84]

Probably the most common you'll see is Aluminum Oxide. This is found in most waterstones, many abrasive belts (e.g. Worksharp). Silicon Carbide is also common, but able to deal with a wider range of upper-end steels. Diamond and CBN (cubic boron nitride, I think is what that stands for) are able to cut any blade steel on the market very effectively. There is also Chromium Oxide which is commonly found in the stropping compounds many of us are familiar with. It works well, but not as much on the vanadium-rich steels or extremely high Rockwell steels. I'm sure there will be others who can chime in and correct me or add, but those are the ones that jump to mind.

 

[HeavyHanded]

https://bosq.home.xs4all.nl/info 20m/grinding_and_honing_part_1.pdf
https://bosq.home.xs4all.nl/info 20m/grinding_and_honing_part_2.pdf

These two cover a lot of natural abrasives.

 

[Bo-dacious]

Peter: yes, cubic Boron nitride is right. Okay, cool. I've heard of those, except chromium oxide, but I didn't know where to find them.

Heavy: okay, I will check those sites out.

Thanks, guys,

Bo

 

[Obsessed with Edges]

'Natural' stones:

Usually implies so-called 'Arkansas' stones in the U.S. They are composed of a natural mineral called 'novaculite' (silica-based). Not very hard (Knoop hardness = ~ 825 or so). These only work well with simple carbon steels and low-alloy stainless, like 1095, CV, 420HC, 440A, etc. Elsewhere in the world, other natural stone types exist. Most all natural stones won't be much harder (abrasive-wise) than the Arkansas stones. All are limited to relatively simple steels without much hard carbide content.

Man-made or 'synthetic' stones / other abrasives:

Aluminum oxide (Al2O3) -> these would include Norton's 'India' stones and many other hardware store-type oilstones, as well as many man-made waterstones. Knoop hardness around ~ 2100; suitable for a lot of middle-of-the-road steels with up to moderate wear-resistance (from something like 440C, 154CM, VG-10 up to something like D2, ZDP-189). Doesn't work quite as well with steels containing more than ~ 3% vanadium, the carbides of which are harder than the abrasive (Knoop hardness for vanadium carbide = ~ 2800 or so). Aluminum oxide is heavily used in many polishing applications (pastes, like Simichrome polish, Flitz, Mother's Mag wheel polish, etc). In such form, these also work well as stropping compounds on the same range of steels noted above. (Edited to add: ) Most 'ceramic' hones used in sharpening are also made with aluminum oxide (usually referred to as 'alumina ceramic').

Silicon carbide (SiC) -> Norton's 'Crystolon' is likely the best-known, but also the old-school 'Carborundum' brand as well. Some hardware store stones will also be in SiC (some ACE branded stones, Gator & others), as with the aluminum oxide oilstones. Knoop hardness around ~ 2600; will do better with more wear-resistant steels and alloys with a more vanadium, at coarser-to-medium finish; not as effective on such steels at higher finish/polishing stages, because SiC still isn't quite as hard as vanadium carbide. Most wet-or-dry sandpaper utilizes SiC abrasive, but some wet/dry paper also uses aluminum oxide.

Diamond -> this is the hardest of all, being the hardest reference material on the Knoop scale, assigned a hardness value of 7000. Works THE BEST with uber-wear-resistant steels having a lot of vanadium content. Think of steels like S30V, S90V, S110V, etc. for sharpening on diamond.

Cubic boron nitride (CBN) -> Also works well with high-vanadium steels. Second place only to diamond in Knoop hardness, at around ~ 4500 or so. CBN is more expensive to produce than synthetic diamond though, so stones made from it can be pricey.

Chrome oxide ('chromium oxide', Cr2O3) -> this is the same stuff originally developed as a powdered pigment for green paint. It's what 'green compound' is ordinarily made of, though some 'green' compounds may be blended with aluminum oxide as well. It's less-hard than aluminum oxide (something like Knoop ~ 1700 or so). Ordinarily only used as a metal buffing/polishing compound; works well on simpler steels with not much wear-resistance (1095, CV, low-alloy stainless like 420HC, etc).

 

[Bo-dacious]

Obsessed: thank you! That is great information. I will definitely read that a few times. Do you know anything about red Corundum? Or what material I should grind with it?

Does anyone else know any other types of materials used in grinding/sanding/sharpening/polishing?

Thanks a lot guys,

Bo

 

[Obsessed with Edges]

Obsessed: thank you! That is great information. I will definitely read that a few times. Do you know anything about red Corundum? Or what material I should grind with it?

Does anyone else know any other types of materials used in grinding/sanding/sharpening/polishing?

Thanks a lot guys,

Bo

'Red corundum' would be another variation of aluminum oxide. In fact, 'corundum' actually IS aluminum oxide, just another name for it. 'Corundum' originally referred to aluminum oxide found in nature. But today, the name is used interchangeably for either natural or manmade aluminum oxide. The 'red' might imply what some mfrs refer to as a 'ruby' aluminum oxide (and real, genuine Ruby is actually a form of aluminum oxide as well). Different colors of aluminum oxide (red, pink, blue, white, grey, brown, etc) come with different crystal shape variations in their makeup, and other properties vary somewhat, like toughness (resistance to fracture), friability (tendency to break down in use), etc. But overall, they're all still aluminum oxide, with essentially the same hardness constraints (Knoop ~ 2100, give or take), and therefore best-used for materials suited for aluminum oxide in general.

 

[annr]

Ceramic?

 

[Obsessed with Edges]

Ceramic?

Most ceramics used in sharpening will be aluminum oxide (a.k.a., 'alumina' ceramic), like Spyderco, Lansky ('Crock Stick'), Fallkniven and many others. Essentially the same hardness limits with them as with other aluminum oxide abrasives.

Some abrasive belts are made with alumina ceramic grit as well, and maybe ceramics of other materials like SiC (not sure, but I think I've heard of these). I think some varieties of waterstones also feature grit of alumina ceramic.

 

[Bo-dacious]

Okay cool. Thank you guys for all this information. Does anyone have any info on the rest of the grinding belts' materials?

Thanks again guys,

Bo

 

[annr]

Most ceramics used in sharpening will be aluminum oxide (a.k.a., 'alumina' ceramic), like Spyderco, Lansky ('Crock Stick'), Fallkniven and many others. Essentially the same hardness limits with them as with other aluminum oxide abrasives.

Some abrasive belts are made with alumina ceramic grit as well, and maybe ceramics of other materials like SiC (not sure, but I think I've heard of these). I think some varieties of waterstones also feature grit of alumina ceramic.

Right. I just wanted the op to consider these. For me, the ceramic honing rods are a powerful addition for maintaining the edge and they perform quite differently from India, for example.

 

[Obsessed with Edges]

Right. I just wanted the op to consider these. For me, the ceramic honing rods are a powerful addition for maintaining the edge and they perform quite differently from India, for example.

I should've remembered to include ceramics in my earlier description of aluminum oxide hones, but overlooked them. Thanks for the reminder.

I've been using a medium grey/brown ceramic lately for touching up, after setting edges on a Fine India. It's a good combination, and one follows the other pretty seamlessly. I started noticing that recently, and reset thinner edges on 3 blades yesterday (Case, Buck in 420HC and 425M) using the India, and immediately following with some further refinement on the brown ceramic after that. Works like a charm.

 

[Obsessed with Edges]

Okay cool. Thank you guys for all this information. Does anyone have any info on the rest of the grinding belts' materials?

Thanks again guys,

Bo

You might also see some belts in 'zirconia alumina', which are also aluminum oxide, but with zirconium added to make the grit tougher and longer-lasting, without breaking down. I think most of those are blue(ish) in color; I have a few of them (Sears brand), and they seem to be as durable as claimed for them. I haven't used them on a grinder (don't have one), but instead have cut them and laid them out affixed to a hard surface, as with sandpaper. At coarser grit, like ~ 80 - 150 or so, they're very handy for really heavy grinding or reshaping of blades. I've used a 120-grit for repairing broken or severely rounded tips on blades, with the belt (3" x 21") cut at the seam, laid flat and glued to a 24" board. Works like a great big file.

 

[annr]

I should've remembered to include ceramics in my earlier description of aluminum oxide hones, but overlooked them. Thanks for the reminder.

I've been using a medium grey/brown ceramic lately for touching up, after setting edges on a Fine India. It's a good combination, and one follows the other pretty seamlessly. I started noticing that recently, and reset thinner edges on 3 blades yesterday (Case, Buck in 420HC and 425M) using the India, and immediately following with some further refinement on the brown ceramic after that. Works like a charm.

My pleasure, plus you are better at explaining than I!

I completely agree with that approach: I've apexed blades, polished edges up to 60K, and maintained those edges for YEARS on ceramic honing rods. Absolutely no need to return to a stone.

I love fine India too, my only beef is that it is not flat enough. I need all of my edges, spines, etc., as true as possible.

 

[samuraistuart]

David, great info. Good post. A lot of good info in one place. As for the blue zirconia belts on a grinder, this is my experience: I bought them when I first received the TW90 grinder (what a machine, btw!), as their price was low, I was new to grinding, and they had a decent reputation. I found out that they work well on annealed steel and wood. Cut well, and had good life. However, when it comes to hardened steel, the performance is just not there. The hard steel kills the blue zirconia pretty quickly. The orange blaze belts hold up MUCH better when grinding an already heat treated blade.

 

[Mo2]

Boron carbide iirc (correct me if I'm wrong please) is about as hard as Vanadium carbides. I've never used it but may get some from Ken Schwartz for stropping in the distant future.

 

[Obsessed with Edges]

David, great info. Good post. A lot of good info in one place. As for the blue zirconia belts on a grinder, this is my experience: I bought them when I first received the TW90 grinder (what a machine, btw!), as their price was low, I was new to grinding, and they had a decent reputation. I found out that they work well on annealed steel and wood. Cut well, and had good life. However, when it comes to hardened steel, the performance is just not there. The hard steel kills the blue zirconia pretty quickly. The orange blaze belts hold up MUCH better when grinding an already heat treated blade.

Thanks Stuart.

I haven't used the zirconia belts on a grinder, so I'm sure I haven't come close to testing the limits of their durability; especially without the heat and extra loads of powered grinding. But as compared to using something like SiC wet/dry by hand, or similar-grit sandpaper in aluminum oxide, I've been impressed at how well they've worked, as I've used them.

 

[FortyTwoBlades]

Boron carbide iirc (correct me if I'm wrong please) is about as hard as Vanadium carbides. I've never used it but may get some from Ken Schwartz for stropping in the distant future.

Boron carbide is a little harder than vanadium carbide, though by a narrow margin compared to CBN and diamond.

Note that within each broad family of abrasives there are different grades of that abrasive, which are sort of like "alloys" of sorts. Each has different performance qualities vs. other grades, and often these grades can be loosely distinguished by color, barring any added colorants. Aluminum oxide comes white, brown (which can also look grey when fired, depending on the process, but is still called "brown"), pink (like a cotton candy pink), ruby, and blue. Silicon carbide is typically seen in either black or green grades. The specific hardness, shape of the grains, their toughness and friability, etc. can all vary depending on their specific composition and manufacturing process, let alone when you get into things like the bond type and strength.

"Ceramics" as the knife community typically calls them (meaning like the Spyderco type of material) are really "sintered ceramics", which use enormous pressure to simply squash the grains so hard that they fuse together rather than being held together by a binder. They will not shed grains to expose fresh cutting surface, and so while they retain their shape very well, they need to be dressed occasionally to refresh the surface as the abrasive grains blunt, which is why so many folks report a lot of burnishing and burr formation when using them--it's typically because they need to refresh their stone (and may be pressing too hard--they're VERY hard stones and not very aggressive.) Bonded abrasives can come in various different sorts of bond types, including vitrified (ceramic, but this is different from sintered ceramics), organic (resin), shellac, rubber, and so on. Each performs differently, ceteris paribus.

 

[bgentry]

This thread is pretty outstanding in it's coverage of many many different types of abrasives. I just wanted to bring up that Spyderco ceramics are supposed to have "synthetic sapphires" embedded in the ceramic matrix, so the cutting action is from both these abrasive particles and from the ceramic substrate itself.

What makes this rather confusing to me is, I've read that "synthetic sapphires" is another way of describing aluminum oxide. Yet the ceramic itself is supposed to be aluminum oxide. I'm guessing these sapphires are a different form of AlO2 than ceramic and a presumably both harder and made of a shape that is more similar to diamond (pointy). But all of that is just guesses.

Brian.

 

[FortyTwoBlades]

It's just a fancy way of describing aluminum oxide. Interestingly, the reason my Arctic Fox series of sharpening stones is blue is for the very same reason that natural blue sapphires are: they have a small amount of iron and titanium in them. So they really are sapphires in that respect. Meanwhile, ruby is aluminum oxide with chromium in it.