Grinding Wheel Wobble

[Tom De Winter]

I’ve got a new 8” Ricon 1/2 hp slow speed grinder. The coarse wheel runs with very little wobble. However the fine wheel has what I believe is excessive wobble. Both have a small amount of runout that can be easily dressed out.

I’ve tried Ricons procedure of turning the flange incrementally and retesting. I feel like I’m chasing my tail. I’m down to about 0.035” side to side wobble. That seems to be as good as it gets.

Am I looking for too much precision?

 

[Gary Beasley]

Maybe you can try one of those centering washers recommended for CBN wheels.

 

[Richard Coers]

Spin the wheel by hand with a pencil held just off the side. Bring the pencil in as it is spinning. It's better to rest the pencil on something to stabilize it. This marks the high spot. Carefully loosen the nut and put a piece of paper between the inside washer and wheel directly opposite the mark. Snug the nut back up and test again. Not unusual for 2-3 thicknesses of paper to bring the wheel up to a smooth rotation.

 

[hockenbery]

Are you turning the wheel?
What I do with a new wheel is rotate it on the shaft until there is the least wobble.
I put a mark on the shaft and one on the wheel and just rotate it 30 degrees lock the nut test and repeat.
Lock it where it had the least wobble Then true the wheel.


[edit] Just saw @Richard Coers post
Similar idea.

Push the wheel into alignment.
If the best position still has a wobble you can push the wheel into alignment by putting the adhesive self stick dots on the wheel under the edge of the washer on opposite sides of the wheel and opposite sides of the shaft. These dots are about .004” thick. This is a technique I learned from Don Geiger.

Put the dots on by-
touch a pencil lightly to the side of the wheel this will leave a short arc the center of which is the “high side of the wobble. The pencil mark is the high side of the wobble. Get some of the round circle stickers 1/2” diameter. Mark where the wheel is on the shaft.Draw a pencil line on the wheel around each washer.

remove the nut and Put a dot each side of the wheel so the center of the dot is on the line around the washer.
You want to push the “high side of the wobble” toward the motor.
To do this the dot on the outside of the wheel goes on the washer circle between the center of the wheel and the High side mark. a second dot goes on the inside on the same line on the washer circle on the opposite side of the center hole.

tighten and check. Keep stacking up the dots until the wheel is running true.
Every time you tighten the nut be sure the wheel is in the same position on the shaft.

 

[john lucas]

Here is my video on truing a grinding wheel. Hope this helps.

View: https://www.youtube.com/watch?v=Wq2tPttFpC8&t=41s

 

[Tom De Winter]

I'll have another go at it today keeping all your suggestions in mind.

John, your "oldest grinder" takes me back to my childhood. My grandfather farmed and had one of these in his tool shed. I used to love sneaking in there and cranking this grinder.

 

[John Torchick]

Had the same problem. Hole in the wheel was drilled at an angle. Call the factory.

 

[Richard Coers]

Had the same problem. Hole in the wheel was drilled at an angle. Call the factory.

The hole is the problem, but drilling is not the way it is put in. Grinding wheels are basically cast. To get the wheel to release from the mold they use a tapered plug to put in casting relief. It's horribly inaccurate and usually makes for a loose fit with the plastic bushing. Now add on a washer that is just stamped with no machining and you get a cheap setup, with predictable issues with running true. They could make all parts of this more accurate, but when a grinder and two wheels sells for around $100, the manufacturing process must relate to the final pricing.

 

[robo hippy]

With my first Rikon 1 hp grinder, the wheels that came with it wobbled so bad, I would not give them to some one I didn't like. With the second one, they were a lot better. Best option would be to get rid of those wheels and then replace them, either one or both, with CBN wheels. This way, you start off with wheels that are both spin and bubble balanced. I also have a video up on You Tube about grinders and truing up a standard wheel. It can be done. You can also get a balancing kit from Oneway. If you go that route, you spend almost as much as you would for a CBN wheel. Some wheels are unbalanced because of the manufacturing system yields a product that is close, but not excellent. Some times rotating the wheel 1/4 or 1/2 a turn will make a difference.

One other thing that can make a difference is the nut that holds the wheel on the grinder. I never thought of it before, but after a chat with Ken Rizza of Woodturnerswonders, he commented that the nuts are not precision made, and that alone can make the wheels wobble. This is where the 'helical' washers come in. One is concave, the other convex. Together, when against the wheel, they can compensate for a lopsided grinder nut. I have yet to experiment with the nuts by putting them in a chuck and facing them off just a tiny bit. I did have fewer wobble issues with my Baldor grinders than I did with my Rikon grinders. Also, if you have to shim out from the motor side of your grinder, you want machined washers, not the stamped ones. Again, they are not precision made, and that can add to the wobble.

robo hippy

 

[John Torchick]

The hole is the problem, but drilling is not the way it is put in. Grinding wheels are basically cast. To get the wheel to release from the mold they use a tapered plug to put in casting relief. It's horribly inaccurate and usually makes for a loose fit with the plastic bushing. Now add on a washer that is just stamped with no machining and you get a cheap setup, with predictable issues with running true. They could make all parts of this more accurate, but when a grinder and two wheels sells for around $100, the manufacturing process must relate to the final pricing.

No matter what the manufacturing process, the hole was at an angle, causing lots of wobble. Got a new one from Rikon.