Safe to dress wheel heavily clogged with aluminum?

sfriedberg · Jul 15, 2019

I've recently started helping out a high school robotics team, and came across a really revolting situation with their 7" bench grinder today. Despite clear labels "DO NOT GRIND ALUMINUM" on both windows/guards, some clueless student spent a long time smearing globs of aluminum into both wheels. Not talking specks of metal in the voids between the grains. Talking protruding blobs 1/8" wide by 1/4 to 1/2" long spanning over the tops of the grains. The noob must have been "grinding" with enough pressure to friction melt/smear the aluminum. :eek:

I immediately asked one of the responsible students to post the grinder as altogether off-limits until we get this cleaned up. Unfortunately, they have no suitable wheel dressers. That's going on their shop shopping list.

In the meantime, I will bring in my dresser and full face shield and try to salvage the wheels. I have NEVER seen loading like this, probably because I didn't previously hang around high school shops. So my questions:

Is it safe to use a Huntington-style (star cutter) dresser on this mess? Will it be effective, or just skid over the aluminum surface deposits?
Is there a better approach? I have single point diamond dressers, but no bulk/mass diamond dressers. Soak the wheels in lye?
Should I advise the shop that the wheels are unsalvagable? I would really prefer to clean them up, but not if I'm likely to explode a wheel or eat a diamond dresser doing it.

Spruewell · Jul 15, 2019

Price out new wheels. Dressing those can be done, but it may not be worth the trouble or the risk. As the aluminum melts/smears into the wheels it can induce a lot of stress and potentially fracture them.

Milland · Jul 15, 2019

Second the new wheels. And add a lock to the switch for the grinder, with a note that the key is held by the instructor, who will check out any work to be done first.

CarbideBob · Jul 16, 2019

Clear the wheel; with a star dress or a diamond as very last resort.
Al plug up is not uncommon.
This occurs all the time, get used to it and do not buy new wheels unless AL grind is the only use of this tool. .
Bob
.

thermite · Jul 16, 2019

Third on new wheels. This is a garden-variety grinder, they are way cheaper than time wasted.

PLUS.. You seem to have LOVELY examples as to "why not grind on shiney-wood".

The OLD ones, AS-IS ...should be hung up on a signboard in easy eyeshot of the grinder with a sterner warning.

NO, REPEAT NO <<FORNICATING>> SHINEY-WOOD!

Page Two:

Add a cheap (even HF can work) belt+disc sander combo and abrasives choices as CAN do shiney-wood with less hassle.

You know you need this. Proof is embedded in those wheels.

Page Three;

Kick ass and take names. The f**kwit who trashed those wheels should pay for the new ones.

Mike1974 · Jul 16, 2019

CarbideBob said:
Clear the wheel; with a star dress or a diamond as very last resort.
Al plug up is not uncommon.
This occurs all the time, get used to it and do not buy new wheels unless AL grind is the only use of this tool. .
Bob
.

I'm with Bob on this. If it is as bad as you say, I would remove the wheel, employ whatever you feel is fitting to remove any excess alum (sharp pick, pointy needle nose pliers, etc) , then dress it to 'like new'.

kenton · Jul 16, 2019

I actually agree with thermite on this, displaying it as an example of why not to grind aluminum on a bench grinder may save you a lot more time and money in the future.

I also agree about the cheap disk/belt sander being a good addition if you have space and budget.

thermite · Jul 16, 2019

Mike1974 said:
I'm with Bob on this. If it is as bad as you say, I would remove the wheel, employ whatever you feel is fitting to remove any excess alum (sharp pick, pointy needle nose pliers, etc) , then dress it to 'like new'.

That could work, too. "Clock it". Shop rates. Fully burdened.

Bill the f**kwit several times the cost of new wheels. That'll learn him!

Mike1974 · Jul 16, 2019

thermite said:
That could work, too. "Clock it". Shop rates. Fully burdened.

Bill the f**kwit several times the cost of new wheels. That'll learn him!

Umm.. high school shop robotics team. No "shop rate", and I imagine that if the same deuche keeps clogging the wheel with aluminum everyone suffers so might as well figure out how to fix it...

thermite · Jul 16, 2019

Mike1974 said:
Umm.. high school shop robotics team. No "shop rate", and I imagine that if the same deuche keeps clogging the wheel with aluminum everyone suffers so might as well figure out how to fix it...

"Prevention" is the wiser goal. "Understanding" is the vehicle.

Appeasement is the wrong answer. ANY training environment.

Sensible use of shared resources - any type - is a major part of what is to be learnt. BTDTGTTS.

Whether the cost of that hits a parent's pocket, a paper-route, or a soldier's paltry pay, small money value, bigger lesson value. Every time. Count on it. Put it to work. It can serve a long life.

"Shop Rate?" That's not hard. US overheads & G&A are hardly EVER less that 100% burden. Just double your jurisdiction's minimum wage. It will never be an overcharge.

Illinoyance · Jul 16, 2019

If you have a Desmond (star wheel) dresser give it a try. Nothing lost but time. I think it might crush the bond under the aluminum releasing the aluminum.

Better yet, get the members to chip in for a Desmond dresser. You really should have some means of maintaining wheel contour.

Rob F. · Jul 16, 2019

If you can get some hard grinding wheels for an angle grinder meant for aluminum then just run the angle grinder against the aluminum load up until it is pretty clean, (both grinders running) then dress as normal. Not to much pressure on the angle grinder, just enough to get the load up off, it will go very fast, these wheels eat aluminum quickly.
The aluminum angle grinder hard discs do a really good job. They are on the soft side so dont last as long as a normal wheel used on steel.
Sait A46N-bf is one that I use a lot of:
SAIT A46N Aluminum Type 27 1/4" Grinding Wheel - Grinding Wheels - Abrasives

thermite · Jul 16, 2019

Illinoyance said:
If you have a Desmond (star wheel) dresser give it a try. Nothing lost but time. I think it might crush the bond under the aluminum releasing the aluminum.

Better yet, get the members to chip in for a Desmond dresser. You really should have some means of maintaining wheel contour.

"Crush" dressers can be had from what? Ten bucks on up? Good idea to learn to maintain wheels.

Just not this FUBAR'ed set. Different lesson in dire need of "implantation", here.

- Read and heed simple guidance.

-Take responsibility for your actions - regardless of their outcome.

A schoolkid, newly entered min-wage civilian gofer, NGO charity volunteer, private sojer, sailor, airman, wannabee leader, manager, NCO, or Officer Candidate, any one, did not "get that" crucial bedrock?

We didn't have any place to ATTACH any other training ONTO!

The potential recipient of the effort cannot be trusted.

That basic. That universal.

Scottl · Jul 16, 2019

IMO the only safe solution is:

Replace the wheels with new ones.

Make the grinder off-limits without instructor permission.

Buy a couple of cheap 1 x 30 belt sanders such as the under-powered but usable ones from HF.

It gives me the shivers to think of the consequences if a high school student were injured by an exploding wheel. Belt sanders are far safer in that environment and the cheapos are low powered enough to stall if pushed too hard.

Many years ago a wheel on a much abused grinder exploded in the service bay at a local garage. Fortunately the young man using it wasn't hurt but the hole in the high ceiling was a dramatic reminder of how much power was released. This was only a six inch grinder with a wire wheel on one side and a grinding wheel on the other.

PS: If you dress the wheels and another "aluminum grinder" injures themselves later the ambulance chaser hired by the family will be assessing the depth of YOUR pockets also. Technically safe or not, I wouldn't do it for liability reasons.

michiganbuck · Jul 16, 2019

Having an old timer hands with all my fingers and knowing the potential of the wheel to try to
bump, bounce and try to catch the dresser I would/might use a ready for sharpening dull brazed tool bit and rub it on the wheel off the bench grinder table. This to get the big slugs off then use the star dresser. And my experience would tell me how to hold the tool bit and the dresser so it could not flip up and get my fingers.

Might rub it with an old broken wheel out of the dumpster, or a broken parting wheel.

*But In a high school shop it is a tough call. Usually if a person is unsure about a job or machine it is best to not touch it.

**It might make a very good example of "Grinding aluminum on most any grinder this is what can happen."
Student would remember that and so good to pass it around every class for them to hold and look at.

Good example of simple loading of steel and other materials, good for them to think about normal loading and dulling grits breaking loose to make new harp grits to engage the work.

If I can find the time I will come out the second Tuesday of next week and dress it for you..ops I will be at Boy Scout camp next week so can't come out. Camp Rotary , Clair Michigan.

g-coder05 · Jul 17, 2019

My hat is off to you. When the shop instructor at my local high school left they needed someone for 2 weeks till the end of school. I am big into wanting kids to learn skilled trades so I jumped right in. Wrong,,,,,, Same thing. Wheels full of aluminum, shafts in lathes just shoved into the quills of the tailstocks. wrenches on the drawbars of the mills with a power bump to loosen or tighten, and so many other things that drove my OCD over the edge. Of course I couldn't just come in and start buying stuff so I went to the maintenance guy and got a bottle of liquid drain cleaner and set the wheels in a bucket OUTSIDE overnight and the next morning they where good as new.

Anyone who can deal with a high school machine shop or welding class as a career has an A+ in my book.

thermite · Jul 17, 2019

g-coder05 said:
went to the maintenance guy and got a bottle of liquid drain cleaner and set the wheels in a bucket OUTSIDE overnight and the next morning they where good as new.

Only maybe. The shiney-wood wudda been dissolved, yes.

The grit bond, nor where the metal salts ended-up in a porous matrix, nor if that might deal-up later surprises from local heating?

I've no klew. So I'd not have risked it for my own use, nor AT ALL where kids of already-known low experience and poor to non-existent safety consciousness were "the environment".

michiganbuck · Jul 17, 2019

thermite said:
Only maybe. The shiney-wood wudda been dissolved, yes.

The grit bond, nor where the metal salts ended-up in a porous matrix, nor if that might deal-up later surprises from local heating?

I've no klew. So I'd not have risked it for my own use, nor AT ALL where kids of already-known low experience and poor to non-existent safety consciousness were "the environment".

Plus likely the blotters would be trashed using liquid drain cleaner, and if you can't trust teens to not grind aluminum then you can't trust them to remember blotters.

I guess a bench grinder needs a crew sheet named "important things about a bench grinder'
1. Be sure rpm of wheel is the same or less than the grinder.
2. Be sure to Ring wheel and use Two Blotters.
4. Check / adjust grinder table to be 1/16 or less away from wheel.
5. wear safety glasses.
6. Be careful.
10. don't grind aluminum.

dalmatiangirl61 · Jul 17, 2019

The Tx shop gets used by all manner of younger non-machinist gearheads, I've written NO ALUMINUM on the grinder, that did not work, so I found a big white shopping bag to cover the grinder and wrote in larger letters NO ALUMINUM, guess what I find every time I use the grinder. I give up!

michiganbuck · Jul 17, 2019

Have a button with a sign "don't touch this" with pushing it you get a spark plug size poke.

I know somebody would sue you, so better not.

Safe to dress wheel heavily clogged with aluminum?

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