hones: sintered-synthetic-ruby vs diamond

[thin-woodsman]

This a follow-up to a post off in some random thread. The question is : how does a sintered-synthetic-ruby stone compare against a high-grit diamond hone?

The ruby is purportedly 3000 grit. Ideally, I would compare it to a 3000 grit diamond hone, but I have a bit of a gap there: my cheap diamond hones (EZ-LAPs, DMT cards) top out at 1200. I have a DMT continuous bench stone at 8000 grit.

A few caveats:

* I did not work very hard or long on this. In fact, it has already taken longer to resize the photos and write up than to do the comparison

* This is not really an apples-to-apples comparison: the grits differ, as do the stone sizes

* The methodology is extremely nonscientific, and the piece of steal was not clean - this is the laboratory equiavlent of not even washing your hands before loading up the petri dish

OK, so I took a piece of HSS lying around (a line boring bar cutter from some huge mill, got as surplus) and cleaned it up a bit using first a coarse bench stone, then both sides of one of those DMT coarse-fine pocket grinders (red and green) designed like a butterfly knife. The diamond stone is a DMT Extra-extra-fine Continuous Diamond Bench Stone (8000 grit), the ruby stone is the largest rectangular stone from one of those 6-for-ten-bucks packs. I made a sharpie line, polished one side of the sharpie line (the end of the HSS piece) on the diamond bench stone until it was shiny, then took the ruby stone and polished on the other side of the sharpie line until it was shiny. Then I went to the microscope and grabbed some pics.

The takeway:

* The ruby stone is much, much faster. Part of this is the coarser grit, of course, but I spent about five times as long using the diamond stone compared with the ruby stone. This can mostly be attributed to loading: the diamond stones load up quickly, the ruby does not. I read up briefly on some blade forum (I think it was actually called BladeForum) and saw that the sintering process provides a tighter bond, so that not only are the abrsive particles not coming loose, there is no metal dust clogging up where they used to be. This sounds great, except the DMT continuous diamond stones are purportedly sintered as well. For the cheaper type of diamond ones, this explanation makes sense.

* The ruby stone cuts deeper. This is definitely due to the grit difference. Much of the diamond side still showed marks from the 1200-grit diamond hone.

* The diamond stone produced a much, much smoother finish where it did cut. Again, this is due to the grit, though it could also be due to the polishing process (work on bench stone, as opposed to hone applied to work in vise).

* I realized that I have been using the 3000 grit ruby hone in place of 1200 grit diamond hones on the bench, because it is faster. The 1200 grit hones are cheap, but not as cheap as the ruby hone - this thing definitely has a good bang for the buck.

I'm kind of curious now how it stacks up against the ceramics. I'm considering putting a bit more time into this and doing a better comparison: I have a 3000 grit ceramic, so a well-prepared piece of steel with the same number of strokes on each stone (ceramic and ruby) should produce similar results.
-

[davidwdyer]

In my experience, diamond loads up quickly without lubrication. I find that diamond with water is excellent for carbide but I wouldn't use it for steel.

[reggie_obe]

What is recommed as lubrication for the Ruby stone? Light oil, Kero, Alcohol, water, nothing?

[eKretz]

A "ruby" hone IS a ceramic hone, FYI. Those hones generally cut very differently depending on how the surface is prepped when they are flattened. If they're coarsely finished they will cut very fast but leave a bit rougher finish on the workpiece. If they're finely finished they will cut very slowly but leave a considerably smoother finish on the workpiece.

DMT diamond plates are not sintered, they are electroplated. That is a completely different process. Sintered hones generally have abrasive contained throughout or at least in a layer at the top say around an ⅛" thick in the case of sintered diamond hones. Electroplated hones have what amounts to a single layer of abrasive particles trapped in place on the surface of the hone with nickel plating. Both can load, both need to be cleaned for the most efficient cutting. Sintered hones can be cleaned by re-lapping or scrubbing with something like Scotch-Brite under running water. Electroplated diamond plates need to be scrubbed with Scotch-Brite or similar and water as well, and using something like Bar Keeper's Friend powdered cleanser is very beneficial.

[elf]

How does the ruby work on carbide?

[eKretz]

They don't. Even silicon carbide has a tough time with carbide. Diamond is king of that realm.

[Bented]

Fascinating subject, if one works in the business of grinding carbide tooling all day long it is a job.
When asked a question about such work, and one answers honestly the replies are awful beginning with:
THIS IS A HOBBY FORUM, NO ONE HERE HAS A $100,000.00 machine

This is all well and good until someone decides to ask, Diamond VS Ruby abrasive.
This may have legs.

Carry on Gentleman (-:

[thin-woodsman]

What is recommed as lubrication for the Ruby stone? Light oil, Kero, Alcohol, water, nothing?

Water, same as diamond. The ruby does not load up as fast as the diamond or ceramic hones/stones.

Ceramic: was referring to the Shaptons I have for the hand planes, Never really looked into the details of those, probably should.

Bented: PM me for an address to send the $100K machine to for testing. Cannot guarantee return

[eKretz]

The Shapton hones use the same abrasive as the ruby hones, except it's crushed into a powder, graded and bound together with a resin or vitreous binder, not sure which they use. The "Ruby" hones are the exact same abrasive but sintered into a solid mass with no binder. The abrasive component of both are composed primarily of aluminum oxide, which is itself a ceramic.

[boslab]

I have still some of these ruby
https://www.gesswein.com/c-326-gesswein-stones.aspx
cant fault them, plenty info on the site
mark

[thin-woodsman]

The Shapton hones use the same abrasive as the ruby hones, except it's crushed into a powder, graded and bound together with a resin or vitreous binder, not sure which they use. The "Ruby" hones are the exact same abrasive but sintered into a solid mass with no binder. The abrasive component of both are composed primarily of aluminum oxide, which is itself a ceramic.

Well, they are the exact same abrasive in these sense that they are all aluminum oxide, as opposed to silicon carbide or CBN or diamond. Supposedly the synthetic ruby is aluminum oxide with chromium, though of course all bets are off with the cheap stones, it could just be food coloring. The Shapton Kuromaku stones are color-coded, but this does not appear to be due to the actual abrasive being used - likely it's the same abrasive in all stones, with a progrssively finer mesh. Shapton appears to be focussed primarily on the flatness of the bench stone, judging by their Glass and Glass Seven lines (in comparison to, say, Gesswein - different products for different purposes obviously).

My thinking so far is that the sintering is what makes the ruby stones work so well, but I wonder if the chromium plays a part.

[BCRider]

Fascinating subject, if one works in the business of grinding carbide tooling all day long it is a job.
When asked a question about such work, and one answers honestly the replies are awful beginning with:
THIS IS A HOBBY FORUM, NO ONE HERE HAS A $100,000.00 machine

This is all well and good until someone decides to ask, Diamond VS Ruby abrasive.
This may have legs.

Carry on Gentleman (-:

Diamond honing is home hobby approachable though. Some time back I watched a video by Stefan Gottswinter on his home shop made slow speed diamond honing "grinder" to be used with diamond discs. The discs are steel and he used super magnets to mount them. Such discs are available as lapidary grinding and polishing discs off Amazon and other places for very reasonable costs. Like even using my poor Kanuckistan Kopeks such discs range from $14 to $30. The finer the grit the more pricey.

And here's the video.... (44) Slowspeed carbide grinder - YouTube

[eKretz]

There is little difference between red aluminum oxide and any other color besides the color. Red contains chromium oxide but it is no harder than plain white. These varieties are all corundum, aluminum oxide, alumina, sapphire; whatever you like to call it. Spyderco for instance makes white alumina hones that work in identical fashion to the ruby red ones I've used. Surface texture of the hone is of great importance in its function; the color of basically none.

Sintering in this case just fuses all the abrasive particles together, as I already mentioned. It doesn't affect the physical properties of the abrasive material. So a hone made in this fashion is either purely formed of abrasive material or nearly so. A hone made with a binder has a much higher percentage of non-abrasive particles.

[Paul Alciatore]

OK, I'll bite. Why not diamond with water for steel? The only problem I know of with using diamond on steel is the heat of a high speed wheel turning the diamond to plain carbon. But hand sharpening at slow speeds and with water to cool the diamond seems to be pretty good protection against that. So, why not?

In my experience, diamond loads up quickly without lubrication. I find that diamond with water is excellent for carbide but I wouldn't use it for steel.

[Paul Alciatore]

Again, I must ask because I just do not know.

"Sintering in this case just fuses all the abrasive particles together, as I already mentioned. It doesn't affect the physical properties of the abrasive material."

But isn't sintering a high temperature process that produces bonds via heat and pressure? Not heated to the melting point, but wouldn't that have some effect on the sharp edges of the abrasive grains? Or not? What is the score here?

There is little difference between red aluminum oxide and any other color besides the color. Red contains chromium oxide but it is no harder than plain white. These varieties are all corundum, aluminum oxide, alumina, sapphire; whatever you like to call it. Spyderco for instance makes white alumina hones that work in identical fashion to the ruby red ones I've used. Surface texture of the hone is of great importance in its function; the color of basically none.

Sintering in this case just fuses all the abrasive particles together, as I already mentioned. It doesn't affect the physical properties of the abrasive material. So a hone made in this fashion is either purely formed of abrasive material or nearly so. A hone made with a binder has a much higher percentage of non-abrasive particles.