EDM Stone Guidance

J. Keeton said:
Gosh this is interesting... may need to try some of these out!

1.) Do yall have to periodically flatten these stones with a DMT lapping plate?
2.) Do yall ride the edge of the stone up the radius of the plunge? Maybe radius the edge of the stones some?
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Not a DMT, you're not trying to cut them, you're trying to fracture them, they're highly friable. An old file works great.
 
I use the stones Tru-Grit sells.
I have only good things to say about them, though I'd like a 1000 grit added to the set, between 800 and 1200.
I use them with water, tried them with WD40 and kerosene and window cleaner, but water seems to work best.
I usually come off the belt grinder at 30 micron and start with a 320 grit stone, go through every grit at alternating angles up to 800, then come back with 600 grit sandpaper to get a final finish, eventually with a soft backing behind the paper.
You use the stones by scrubbing with the tip. I periodically reshape the stone on a 60 or 120 grit belt to add a radius to the tip, just to reduce the surface area in contact with the blade.
 
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Nathan the Machinist said:
Not a DMT, you're not trying to cut them, you're trying to fracture them, they're highly friable. An old file works great.
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The DMT diamonds are monocrystalline and not very friable. however, they're set in the surface of the hone with an electroplate method, which doesn't hold the large diamonds very well.

They leave the electroplate quickly and will leave a void behind, leaving the remaining stones that are finer still cutting. Eventually, those will dull, but I've taken microscope pictures of various inexpensive diamond hones and the particles even when they're dull stay there - except the big ones - the big ones leave almost right away.

They also pose an initial problem in a polishing process - very deep stray scratches. The grading of the diamonds is not very good compared to lapidary powders which can be applied to a piece of smooth cast iron and used like a diamond hone as long as one is polishing hardened steel.

Here is a picture from a brand new 400 grit side on a monocrystalline diamond hone - these are done on a flat surface (the back side of a chisel that's probably 60-62 hardness, but relatively plain tool steel:

Hardened steel - new 400 grit diamond hone

same hone new, 1000 grit

A much older and well worn atoma 400 grit diamond hone:

I have others of the first two stone that are worn, and they are about as slow as the atoma - just a view of the two 400s in comparison shows how things change when the big diamonds have been pulled off of the electroplate.

This causes woodworkers to conclude that even though they're casual users, that their diamond hones "wore out right away".

Ezelap used to offer diamond hones with monocrystalline diamonds (more prone to fracture and even and sharp, if becoming finer, cut), but the last time I read their specs, that had gone to a mix at least. I'm not a diamond expert, but at the time understood that monocrystalline diamonds were cheaper. DMT touted them.

I think if diamonds aren't absolutely needed, friable silicon carbide will leave a lot less follow up work and stray scratching.

Very fine cheap diamond lapidary works great in cast iron or for very fine finishes, even wood - if the diamonds are cheap enough. 1 micron in wood will leave a blindingly bright level of polish that my microscope doesn't see as having any visible scratches.

Far beyond an 8000 grit waterstone polish

Autosol on hardwood is also very good at a very bright polish finish without eliminating crisp lines.

(I see that EDMs are offered both in alumina and silicon carbide. Both are good choices depending on whether the hardness of the stones fit the use. Sharpening side, they look identical to india and crystolon stones, respectively, which also vary a good bit in hardness. Older fine carborundum stones may also be useful - they usually shed grit pretty easily and can be found in high levels of fineness and often in groups of stones for almost nothing).
 
Nathan the Machinist said:
Not a DMT, you're not trying to cut them, you're trying to fracture them, they're highly friable. An old file works great.
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Sorry if my post above sounds like i'm lecturing or unfriendly, wasn't my point. In the woodworking community, we all thought they were fracturing, too, until a long-time phd research chemist who has a habit of asking manufacturers technical questions gave us the what's up about the popularity of monocrystalline now due to their low cost (this is a 15 years old comment, this change - or much more), and then I stuck my diamond hones under the microscope remembering this later, and he was right. The big diamonds are gone in a hurry. the picture of the remaining diamonds gets more and more cruddy looking, I'm assume as the very tips of the remaining diamonds may wear/dull or the sharpest bits may fracture.

I have a fascination with sharpening and abrasives and the pictures aren't intended to be definitive or pushy, just that I have them from bits of info I've collected over the years and then checked to see if I could see them. The fine polishing stuff was put together because woodworkers always claim to want a fast fine edge, and some things are better at the fine and hardly slower. Whatever the alumina is in autosol, it doesn't scratch deep - a check of the MSDS would probably find it to be calcined alumina (disks instead of balls....never mind, I just looked and failed to remember that alumina isn't toxic so they're probably not going to list the exact abrasive if they don't have to).
 
D-weaver said:
Sorry if my post above sounds like i'm lecturing or unfriendly, wasn't my point. In the woodworking community, we all thought they were fracturing, too, until a long-time phd research chemist who has a habit of asking manufacturers technical questions gave us the what's up about the popularity of monocrystalline now due to their low cost (this is a 15 years old comment, this change - or much more), and then I stuck my diamond hones under the microscope remembering this later, and he was right. The big diamonds are gone in a hurry. the picture of the remaining diamonds gets more and more cruddy looking, I'm assume as the very tips of the remaining diamonds may wear/dull or the sharpest bits may fracture.

I have a fascination with sharpening and abrasives and the pictures aren't intended to be definitive or pushy, just that I have them from bits of info I've collected over the years and then checked to see if I could see them. The fine polishing stuff was put together because woodworkers always claim to want a fast fine edge, and some things are better at the fine and hardly slower. Whatever the alumina is in autosol, it doesn't scratch deep - a check of the MSDS would probably find it to be calcined alumina (disks instead of balls....never mind, I just looked and failed to remember that alumina isn't toxic so they're probably not going to list the exact abrasive if they don't have to).
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You missed Nathan's point. We are talking about EDM stones. Nathan is pointing out that the EDM stones are friable and can be shaped effectively with a file, rather than a DMT.
 
Richard338 said:
You missed Nathan's point. We are talking about EDM stones. Nathan is pointing out that the EDM stones are friable and can be shaped effectively with a file, rather than a DMT.
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You're right, I was eating lunch and misread it, and looking to see what the EDM stones were made of at the same time. My apologies.

The only useful bit of information for anyone in my post above is not using diamond hones (which nobody asked) for polishing work, and the comment does stand that if you see a bag or box full of unused carborundum stones at a flea market for $5, you'll probably find them useful for doing the same thing as EDM stones.
 
Has anyone tried the stones with a reciprocating profiler? (for example boride abrasives has a bunch)
 
J. Keeton said:
Thanks for that video... I didn't envision them used like that (like a chisel).

I was thinking you'd use them like a normal sanding bar; contacting the whole height of the bevel.
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Your welcome. It's how I've been doing it. I've been please with the results.
 
I know this thread goes back a few years but just noticed that Falcon Tools has their EDM stones in small, mixed sets right now. Standard set of 5 or six, mixed grits for less than $50.
Big savings over buying a dozen of one grit.
 
DanF said:
I know this thread goes back a few years but just noticed that Falcon Tools has their EDM stones in small, mixed sets right now. Standard set of 5 or six, mixed grits for less than $50.
Big savings over buying a dozen of one grit.
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This what I have been looking for; will the EDM stones work equally well prior to and after heat treating? Or do you recommend a different type? Also, what thickness is preffered, 1/8" or 1/4"? Thank you
 
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I will let someone with more experience with the EDM stones answer, some of the earlier respondants to this thread from a couple years ago are very well-versed in their use and if I recall correctly, Nathan the Machinist Nathan the Machinist prefers the type N (or did back then).
I have used a different brand up to this point, but did not like them.
 
I have used the Gesswein Blue (harder) and White (softer), CBRIGHT on the big river site and the ones from usaknifemaker Falcon EDM dark browns.

I went from a rough 220/320 belt finish (with leftover deeper scratches) to a 400 grit edm stone finish on a 4" hardened Magnacut blade in about 10 minutes per side, using just the 400 grit stone.
 
Taz said:
I have used the Gesswein Blue (harder) and White (softer), CBRIGHT on the big river site and the ones from usaknifemaker Falcon EDM dark browns.

I went from a rough 220/320 belt finish (with leftover deeper scratches) to a 400 grit edm stone finish on a 4" hardened Magnacut blade in about 10 minutes per side, using just the 400 grit stone.
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Thank you for your response; if you were to buy new ones today based upon your experience with them, which would you choose between Falcon, and CBright? These will be used on untreated 1095.
 
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They are best on heat treated hardened steel. I would go with Falcon N series. The ones I have are a bit harder and can leave gouges.
 
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