Bench grinders in the Metal Shop

Metal Shop
#21

I’m feeling the need to expound on the responses to @Nate by way of explanation.
The grinding wheels we stock in Metal Shop are intended to grind ferrous materials. The grit is intended to sacrifice itself during the material removal process, which is why the wheels wear. The sparks you see flying when steel is being ground is because the heated material, and a fleck of grinding wheel, are being expelled. The wheel absorbs some heat. The material absorbs some heat. And the flying debris carries some heat away with it.

The reason you don’t see sparks with aluminum, and why soft materials like aluminum “load up” the wheel, is that the grit is too hard to self-sacrifice, leading to a build up of soft metal in the grit. Instead of expulsion of heat, metal, and grit, you end up transferring all of that to the wheel. This doesn’t seem like a big deal. You just dress the wheel (using a dressing wheel to remove a bit of the surface of the wheel, and, hypothetically, the aluminum with it), right? Nope. Because the semi-molten materials travel below the surface and impregnates the wheel. Why is this “dangerous”? Because the next time the wheel heats up, the (now solid) metal will expand, causing fissures in the wheel’s structure. Then the forces at work in a thing spinning really fast causes the fissures to manifest in cracking, breaking, and projectile events (i.e. “fly apart and chuck chunks at high rates of speed”).

THIS is why we don’t grind aluminum or other soft metals on grinding wheels which are not intended for that work.
THIS is why people who’ve been around this for any length of time get REAL TOUCHY about it, too. It’s not just that it’s dangerous. It’s that it’s unpredictably dangerous to everybody in the vicinity.
I am unclear on why people continue to ignore the advice and/or signs, and therefore have no idea how to reach out to folks who continue doing this…
Seriously, there’re belt sanders right there that will take on aluminum grinding happily…

4 Likes
#22

Having had wheels fracture and throw themselves at me before, I can’t stress enough how big of a deal this can become no matter how innocuous it seems to the average user.

Trying to educate on this, among other issues, is one of the reasons I want to implement a Metal 101, but unlike Woodshop where they have a very large instruction base that reduces our options. It doesn’t help that the camera on that spot has been broken for quite some time and Infrastructure still hasn’t pulled a new cable yet.

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#23

Is the camera broken or is it the cable? You can pull the cable on your own. I volunteer occasionally to pull cable but I won’t have time to do it anytime soon.

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#24

I appreciate the more in depth explanation. I was aware of the dangers it poses but I’m glad people who still think it’s no big deal might see this and realize the issues. Using the word “signs” in my post was probably a mistake but it was the simplest way I could think to word it lol

3 Likes
#25

I think “if you build it, they will come”.
I’d happily teach a MS 101, but as often as I’ve offered to help (and tried on my own to) apperate a course into existence, we’re still without one to the best of my knowledge. Let’s do a 2 session “build the class and train the trainer” followed by an instructor drive. I think that’s how Woodshop did theirs: first the class, then the instructors will come. We’ve already got a slight head of steam on working to streamline the Welding/Safety courses. Let’s see if we can’t carry it on…

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#26

I think your request was perfect!
And it allowed @Photomancer David to pull a little double-entendre joke. Everybody wins!

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#27

How clever I am, just do it without intending to!

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#28

Can you not grind aluminum with a flapper sandpaper wheel? What are acceptable ways to grind aluminum?

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#29

I’m glad you asked!

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#30

If you are talking about the camera at the welding end of the room, I replaced the connector on the end of the cable. It worked for a short time and quit again. I thought someone else had pulled a new cable and it did not fix the problem either.

When we are running cameras for the expansion, we should try replacing that camera with a new one and testing that one under different conditions. Also we are having persistent problems with random cameras dropping in and out that we think is a problem with the current servers. More and better servers with the expansion should fix that problem.

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#31

Thanks all for your answers, my main goal in posting was education for my self on how to tell by sight if someone is grinding what they shouldn’t but I’m glad there was so much more info added so others can refer to this thread with questions on this stuff!

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#32

This. This right here is why I stay out of metal and machine shop haha honestly I would love, I guess you would call it a safety tour, don’t even have to teach anyone how to actually use anything in detail just a quick demo or rundown of the name and what it’s for and general safety rules.

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#33

I was told a new cable hadn’t been pulled, and that the problem lies there. However, I haven’t gotten up there with a cable tester myself.

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#34

I have reviewed video from Friday afternoon til Saturday about 12 noon. I found thus far 1 offender.

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#35

Sad to say I am no surprised. It keeps happening. I apologize for not being more diligent while noticing it, I will make sure to take a second look next time I see it. Hey @hon1nbo and @TBJK can you both message me your number so if I see a possible infraction again I can call you to issue an interim ban?