Pinging Harold & Susan

I think you'll notice that the surface speed of these devices is well below a critical threshold. Where the problems begin is at red heat. If diamond is run on steel at low surface speed, such that it doesn't get hot----no problem. Once up to the heat of ignition, however, carbon begins transferring to iron, which has an affinity for carbon. This process rapidly dulls diamond. If you touch the base metal of brazed carbide tools to the diamond wheel (it happens occasionally), there is an almost instant change in grinding characteristics. It can be attributed to some loading of the wheel, but the diamond is also dulled in the process. The wheel often requires dressing to restore its qualities.

Regards the expected life of the wheels you have now---it all depends on the nature of the wheel. High quality diamond wheels are a layer of matrix (there are various bonds---metallic, resinoid, and more), filled to various degrees, with diamond. The layer thickness and degree of concentration dictate useful life. Needless to say, a 100% concentration that is 1/8" thick will outlast (and out-perform) a wheel that has 25% concentration and is 1/16" thick. It stands to reason that the higher the concentration, the less the matrix is abraded, and the faster the wheel will cut. The wheel of choice for grinding (brazed carbide) toolbits is a resinoid bond, but it should not be applied freehand. A rest is a definite advantage, and steady coolant is required. Drip can cause more damage than none at all, due to thermal fracturing.

Damned shame about the loss of Oscar Peterson. What a treasure he was.

Harold

Thanks for that explanation. Despite I didn't ask. ;-)

And a happy new year!

Nick

How do you dress diamond wheels? I wasn't aware they could be dressed, but I've never had much to do with them, except for some old castoffs I salvaged.

-- Ed Huntress

I've also ment to ask about steel and diamond. Do you have an idea on what surface speed is acceptable?

Wes

Oh, wait a minute. Are you talking about using a single-point diamond to dress diamond wheels on a surface grinder? That I've seen. I was thinking about the wheels on a bench grinder. Can you dress them the same way?

-- Ed Huntress

Ed,

Thanks, Wes. Verrry interesting. Have you done this? How fast does an aluminum oxide stick wear when you're dressing diamond? I assume it just shatters the diamonds, right? Or does it pull a layer completely out of the matrix, exposing a new layer?

-- Ed Huntress

I've never used the things for their intended use. We have them at work. I believe to dress the diamond wheel dressing wheels that dress our cbn grinding wheels.

I have used them to clean up a locating ring on a special chuck after the operators spin a part on it. Remove the clamping arms, defeat the interlocks, spin it up to 2500 rpm and hold the dressing stick against the locating ring. Gitter done. Stick breaks down really quick on steel and conforms to the ring while removing the boogers. Recenter the chuck on a

Wes

Hmm. OK. I'm still curious about an aluminum oxide dressing stick on diamond, though. That one threw me.

-- Ed Huntress

I think we are going to have to wait for Harold on that part.

Wes

Sorry, Wes, I can only guess. Carbon combusts at something like 1,100° F, so I'm inclined to think that it starts to occur at that temperature.

Norton did research on this subject back in the 50's, although I've never read any of the reports. Could be you could learn more on their web site. I've never bothered to look, so I have no clue.

Harold

Funny, suddenly I'm not seeing Ed's posts. MY damned ISP has been nothing short of a PITA of late.

While I've used a dressing stick on my diamond wheel on rare occasion, I avoid its use as much as is possible, for obvious reasons.

My casual observation indicates it tends to abrade the matrix, not so much the diamond, which feely cuts aluminum oxide or silicon carbide. By removing a small amount of the matrix, old diamond is released and new diamond exposed. It's a combination of cleaning the wheel and changing the exposed abrasive. Often the problem with a diamond wheel is loading---while the diamond remains quite sharp. That's one of the best reasons to run a diamond wheel wet---to keep it from loading. It makes a huge difference in performance. Keeping soft materials off helps, too (steel, for example).

Harold

Hmm ... aside from the matter of speed which Harold covered (and I think that the Drill Doctor is still pretty fast -- I could measure it with a StroboTac, but it is also pretty small in diameter -- less than an inch I think) -- but the Drill Doctor is *also* sold for carbide masonry bits -- thus making the diamond necessary for that. Otherwise, I would have prefered something like CBN. (Hmm ... how does that do in sharpening carbide?

Enjoy, DoN.

With a single-point diamond dresser. Same as you use for carbide wheels. These are surprisingly cheap, for 1/4 carat or so.

Jon

Yes, of course, but your results will be as accurate as your hands are. With a light touch so the low spots in the wheel don't "draw in" the dresser, you can do pretty well. Mostly, I've used this to dress toolpost grinder wheels on the lathe or diamond wheels on the mill, but I have done it freehand a few times in special cases.

Jon

What's the mechanism of action? Does it just sheer the diamond grit out of the matrix, or does it fracture the particles of grit?

-- Ed Huntress

I'd suggest it works on the matrix, but it will be equally as hard on the diamond used for dressing. You end up with diamond against diamond in any case.

While the notion of dressing a diamond wheel with a diamond likely works, I'd avoid it like the plague. The layer of diamond in wheels is finite----to dress away any of it, especially by hand, is not, in my opinion, the smart thing to do. Diamond wheels are made true----so if they run out, look elsewhere for the problems and address the error(s) in question. Don't dress a good wheel to a bad mounting, in other words. By dressing, you could easily ruin a wheel, or, at best, shorten its useful life tremendously.

Dressing sticks do very little damage to diamond wheels, mostly just clearing them of loading. Stick with dressing sticks, and use them only when necessary.

Harold

I've seen two mechanisms to give better results.

• You have a tool rest in front of the grinder, and you make a jig to go around the diamond point dresser (essentially something with a hole for the dresser). The top of the jig is held against the bottom of the tool rest. You might be able to use some sort of clamp, or Vice-grip.
• Woodturners use a grinding jig called Wolverine, and it has a diamond point dresser option. However - it's pricy. It essentially does the same thing.