Grinding-wheel safety

Thanks Nick,

We had the same experience a couple of weeks ago. One of our guys jambed a bar in one of Cincinati Centerless grinder and a 20x8x12 wheel exploded. When the guy came to see me and explain how he "cracked" the grinding wheel,I've never seen quite that color of white on a human before. No one was hurt, but I do understand that the guy's undies will never be the same. When we replaced the wheel, I had them run the machine for an hour before dressing it and putting it into production.

Greg

Thanks Nick! We now run new and remounted wheels for a half hour or so.

Interesting shade of color, isn't it?

Better to be on the save side! Before getting bored with too long a break in time (pun intended), I gave you these numbers. But if that 1/2 an hour rule is an accepted rule in you shop, you already won. And I don't think that the one who had the mishap will be the first to break it.

Don't ask me how they got these numbers!

Nick

Kind of a cross between the palor of death and the white cliffs of Dover...

Heh!

Years ago, in the early 60's, we used to grind a short piece (3" long) of

3½" diameter steel that had two holes bored in it, and was used to house some electronic gear that was potted in the holes. This item was part of the flight equipment of the Sergeant Missile.

We had only one centerless, a #2 Cincinnati. Anyone that has operated them knows that they're a 3" machine, but if you use a short blade and run well above center, you can grind larger items, although at the expense of traction. It's always dicey---you can hear the parts trying to leave the blade, but we had good luck, although with considerable rumble, ----except once. I came in one morning to find a huge divot out of the wheel, which in this case was only 6" wide. One of the parts jumped out of the wheels and came down sideways. They tell me ol' Musselman looked a great deal like the guy you described. :-)

The wheel was slammed to a stop, but didn't break. We dressed it down past the divot and continued using it. Couldn't say the same for the carbide blade, which was shattered.

Harold

I would think this would have also been a good place to mention ringing the wheel. We used to ring 36" wheels, mount them on the flanges, balance, and then run about a minute before using. Following that procedure, I never saw a wheel break in the 69 months I worked in the Grinding Shop at Naval Aviation Depot, Jacksonville.

Oh, I thought that everybody knows that. The discussion was what else to do to avoid a fracture.

OK, whenever you mount a disk (new or used), ring it first. If it sounds dull, dump it!

Nick

No-------if it sounds dull------BREAK IT! Make damned sure it can't be used.

You may save some poor fool's life.

Harold

OK - I'll bite. What is "ringing the wheel" and why is it important?

Thanks

Suspend the wheel on something through the center hole (a screwdriver workd well for this) and tap it with something relatively solid (a hard plastic screwdriver handle workes well for this) and listen to the noise it makes.

If the wheel rings like a bell, with a clean note, it can be considered to be solid. If the noise is a flat "thunk" then there is a very good likelyhood that the wheel is cracked, and could blow apart on startup or in use.

People have been killed by grindstones coming apart.

Read and follow the instructions on the label of the stone. Never run a stone that does not have the labels to pad the stone against the clamping pressure of the washers. Grinding wheels that do not ring true are to be smacked with a hammer, and then disposed of.

Cheers Trevor Jones

So what makes a good replacement blotter?

Serious question, I can't imagine tossing out a wheel just because its blotters are missing or damaged. Maybe some gasket material?

You do know why they are called blotters don't you?

Good thick blotting paper is very good. Otherwise, try bits cut from a cereal packet!

Mark Rand RTFM

Yet another use for empty pizza boxes.

John

Cereal box.

Yet another good reason to eat your Wheaties!

Cheers Trevor Jones

Yep! What Mark said!

The idea of using a pizza box, as already mentioned, is probably not a good one unless it's not corrugated. The blotter must be able to absorb irregularities and still provide good clamping power. I can't see the corrugation providing the same kind of service. There would be far too much thickness for the typical adapter, anyway.

Harold

Thanks everyone. I was thinking cereal box or similar type of cardboard but didn't quite dare suggest it here. I quite often save heavy card board pieces (not corrugated) for future use. It makes good lifter/protector page in binder style notebooks too. Much better than the plastic crap that comes with them and then splits into pieces after a year or two.

And to Trevor, nowadays it is Bran cereal. Gotta have some roughage to soak up all that beer and move it through :)

Long live "honey Nut Cheerios" Gerry :-)} London, Canada

You got to remember to ask the pizza shop what type of boxes he is using. If you use the pizza box for the pads on the wheel, are you able to write off the cost of the pizza and the delivery as a business expense? :)

John