This is an abrasive disk, rotating at 1500 rpm. When I shine my flashlight at it, it carries the glow with it, approximately halfway around the disk. What am I seeing happen here?
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I’m guessing it’s an aluminum oxide abrasive? The abrasive is flourescing due to the little bit of uv coming out of the LEDs.
You might find this interesting, if you are grinding iron or steel then the grinding surface may not flouresce due to the iron bonding with the aluminum oxide.
This seems like a perfectly reasonable answer. OP! You could probably test this by changing the type of light you’re using. Try a red laser pointer as a control, and a black light wand (the sort they use to detect counterfiet bills), and see what happens.
Sadly I have neither of these things available on hand to test that theory but I can at least confirm that the abrasive wheel is a ceramic alumina.
Actually NVM, I found a laser pointer and it has no effect, though it is admittedly quite dim.
Complete tangent, but alumina, aka aluminum oxide, is usually considered the second hardest naturally occurring material. When it is found in nature, it is given the mineral name corundum and is clear. But if there are some impurities in it, you can get colours. Red corundum is called Ruby, and blue is called Sapphire. In the beauty industry, the same material (mixed with magnetite) is called emery, and lends its name to emery board, and is used in nail files. In the tech industry, it’s used to make the extremely scratch resistant coating on most modern phone screens (basically nothing but diamond will scratch it).
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We also use emery paper to smooth out rough surface finishes on machined parts. None of my tools but some of the tools the other guys have in the shop use little Ruby beads as reference surfaces. Our wire EDM also uses Ruby for some critical parts.
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Fun fact, machinists do not have friends. Only mortal and natural enemies.
So… night shift?
It sounds like you got the answer to your question, so I need to ask, what the heck weird kind of flashlight is that?
It’s a cheap LED pen light, they hand them out like candy where I work. Most of us have our own flashlights anymore.
What effect are you talking about? Is there a frog clinging to the underside of that stone, and you try to coax him out with a flash light?
