Tool Time: Anyone have this problem with wire wheels?
 

I have a large bench grinder/polisher. 3/4" arbor, 3/4hp. Weighs a good 60 lbs. or so. Grinding wheel on one end and rag wheel on the other. Today, I swapped out the buffing wheel for a wire wheel, fired the sucker up and it started shaking like Katherine Hepburn's head in a helicopter. I tried another wire wheel and same thing. Grinder runs @ 3600rpm. Wire wheels are rated for 4500rpm.

The machine is bolted down firmly to a workbench, however the workbench may not be sturdy enough for the machine.

Has anyone else experienced this when using wire wheels? Will bolting the grinder to a proper stand (bolted to the floor) help? Why the heck would a wire wheel vibrate so badly?

:confused:

If the hole on the wire wheel is 1" diameter by chance and uses those silly cup washers to help center the wheel up, the only thing I can think of is that the wire wheel is mounted off center of the arbor (the washers aren't helping in other words) which is causing it to shake so bad.

Think of a washing machine on spin cycle with all the bathroom towels on one side of the bucket...

I just had a very similiar problem. I found that the build quailty of the (brass in this case) wheel was very poor. On careful inspection I saw that ther was a larger concentration of "wire" at one point on the wheel. This was also the point where the wheel would come to a stop after switching off. In short this particular wheel was terribly out of balance. I thought about trying to fix it but decided on just buying another. The second one was OK. Now both of these wheels were inexpensive and had I not found joy on the second I would have most likely invested more money in hopefully a better wheel bought somewhere else. These were from Lowes and little selection could be had.

I tried two different wheels with two different mount styles. One uses the washers and one uses a sized insert. Both provided the same results.

Both wheels were inexpensive (Made in China), so I suspect that's part of the issue. However, finding wire wheels to fit a 3/4" arbor is difficult (most are either 1/2" or 5/8"). I had to buy what I could find.

Check the rpm of the grinder, and then check the rpm rating of the wheel. they should be the same. If not, the wheel might have been balanced to a lower specification and thus not safe for use.

Bench Grinder is rated @ 3600rpm. Wire wheel(s) are rated @ (not to exceed) 4500rpm. So...that shouldn't be a problem. I'm not spinning the wire wheels too fast.

I think you've hit the nail on the head. The dreaded "Made in China" problem. Sadly, my experience has often been that they make a part that looks just like the good ones, but when you go to use it....

I'd look for an adapter that will allow you to use readliy available wheels and then buy them from a reputable vendor. Have you tried Grainger's, McMaster Carr, or a similar source? Hopefully they still sell the good stuff.

JR

My wire wheel machine isn't bolted down, and it moves all over the place from vibration. I doubt the wheels are well balanced, and I doubt there is much you can do about it.

how big is the WW
maybe a smaller one would be more stable

A pedestal type grinder will vibrate worse than a bench type given all else is the same. Like others have mentioned, probably the China syndrome once again.

that's nice....

may you never have such an affliction.

Tell it to this guy...it's his quote. I have no original thoughts:

http://www.grabow.biz/images/DennisMiller.jpg

8".

Problem with fitting smaller wheels is that you throw off the rpm ratings of the wheel. An 8" wheel spinning @ 3600rpm is slower than a 6" wheel at the same rpm....(right?). You can easily exceed the rating of the 6" wheel by installing it on an 8" machine.

How 'bout a larger wheel (e.g. 10")? More mass = more stability? :confused:

I'm thinking a cast-iron pedestal bolted to a concrete floor will be less vibration prone than a free standing wood workbench... :confused:

RPM is controlled by the motor, not the size of the wheel. The shaft will turn the same rpm whether the attached wheel is 1 inch or 100 inches.

Yeah, I may not have presented that correctly. I'm trying to say...if the bench grinder is designed for 8" wheels @ 3600rpm and I install a 6" wheel on it that was rated for 3600rpm, would I be exceeding the limits of the 6" wheel? Guess not... 3600rpm is 3600rpm, right?

Right. The only difference is the 8 inch wheel will have a greater "tip" speed. It's making the same revolutions pre minute but it has a greater circumference, thus the actual bristles at the point of contact with the work are traveling faster.

JR

On wood lathes they pile bags of sand on the base when they turn something unbalanced.