Die grinder vibration problem

My old die grinder seems to run smooth as silk when there is no bit / burr in it.

As soon as I put in a burr and turn it on, it has an out-of-round vibration. It's almost not enough to see with your eye
but you can hear it and feel it, and when you try to put it to a surface to grind on, it jumps around in an unsafe manner.

The burr has a short 2-in shank and the diameter of the cutter head is only about 1/2 inch.

So the vibration must be from the burr. It was $23 twenty years ago and is brand new / undamaged.

Are the TIR tolerances that tight on a 26,000 RPM cutting burr ?

Where do you buy quality burrs these days that don't vibrate ?

My solution was to slow the die grinder down a little. I used a router speed controller from harbor freight. Seems like the burrs cut better, last longer, and the sanding rolls really last longer. easier on my hands as well. But as you said any of the long shank burs will vibrate at full speed, even had some of the sanding roll holders bend from the vibration at full speed.

Hmm fascinating. Total news to me, I'm not a woodworker.

JWB, What RPM do you use to grind aluminum ?

Sounds like u need a new grinder. Probably the bearing has some play. I use a flex shaft fordom.

When I was using electric die grinders I used to order bearings by the dozen !! And I always had to handle the grinders with welder's gloves 'cause they got so hot. For the past 30+ years I've been using pneumatic die grinders. Even cheapies are more durable than the electric ones.

For what they cost, go buy a new one and see what happens. If the new one has no vibe then toss out the old one.

HI

if you use the sealed bearings they get hot at the hi speed of a die grinder , you must use the metal shield type to avoid the heat buildup !

I bought some cheap carbide burrs and they had a 6mm (.236) shank instead of .250. Caused the same problem till I checked them and found out.

The controller is not calibrated in rpm, but high to low, I usually set it at medium. I use grinding oil on the burrs, slowing down the speed helps keep the flutes from clogging as well. I used air die grinders for years, seems the rpm was never constant with them, different from model to model and as the wore out the rpm decreased.


https://www.amazon.com/Newest-Varia...;hvtargid=pla-4584070141937617&psc=1

Here’s a post we had on Abodiesonly about burrs. I will be buying more in the future

https://www.forabodiesonly.com/mopar/threads/killer-carbide-review-update-with-video.509680/page-3

I would get a new collet.

that may very well be the way to go.
i have seen collets deformed by tightening up on undersized tooling shanks. this can also booger up the female receiving cavity, possibly rendering the tool useless unless the output shaft of the tool is replaced.
just my personal experience using these tools.
your mileage will vary.

A new collet is is a good idea.