repair of grinding wheels

[Randy McCreight]

Is there any interest in fixturing and lathe modifications?

Several years ago, I bought a slow speed bench grinder with 8 inch wheels for sharpening my woodturning tools. Recently, I noticed that I could not sharpen my bowl gouges properly, even after dressing the wheels: the gouge bounced on the surface of the wheel, and I could not get a smooth cut on my bowls. When I removed the wheels, I noticed that the hubs were simply epoxy that has crumbled partially, permitting the wheels to move off-center on the axle.
Could I rebuild the hubs? Sure. But how? I wanted the mounting holes to be centered on the circumference and square with the sides of the wheels. I decided to make aluminum bushings to epoxy into the wheels and to mount the wheels on a faceplate to bore the center holes.
I used my Dremel tool with sanding drum to remove most of the epoxy from the wheels. I turned two aluminum bushings, about .850" diameter with 1/2" hole, that fit loosely in the wheels. I used Devcon epoxy to hold the bushings in the rough center holes.
I made the faceplate from a scrap of baltic birch plywood, screwed and glued onto a mesquite tenon clamped in my Nova chuck. I turned a pocket into the faceplate to center the perimeter of the wheel. I clamped the wheel to the faceplate with an assortment of T-nuts, flat head screws, fender washers, and #8 wood screws. I bored the aluminum hubs to fit the axles on the grinder.
The accompanying photos show the construction of the faceplate, the pocket turned on the faceplate, the wheel mounted to the faceplate, and an early bowl. The mounting hole is off-center in the bushing but centered in the wheel, square to the sides of the wheel.
The wheels grind much better now.

[John K Jordan]

Interesting idea and clever method and fix!

But yikes - I wonder what caused the crumbling in the first place I've not once seen that in decades of grinding. Perhaps the nut had loosened?

JKJ

[Randy McCreight]

The epoxy wasn't very strong. Maybe the nut wasn't tight enough, but the wheel never slipped.

[John Keeton]

Interesting project, Randy. Not sure I would go to the effort to save a couple of used AO wheels that could be replaced for less than $40 and not have to worry about another epoxy failure, but if you enjoyed the project that is really what matters anyway.

[John K Jordan]

The epoxy wasn't very strong. Maybe the nut wasn't tight enough, but the wheel never slipped.

Sounds like it's now stronger than the original, but if it fails again swing by here and I'll give you a new wheel I took off a grinder. I have a stack of them somewhere from when I switched first to Norton 3X then to CBN wheels.

If you haven't done so, you might repeat the "ring test" to make sure the wheel didn't develop an invisible crack from the hub out when it was bouncing around. It would be frightening if the wheel came apart!

JKJ

[Randy McCreight]

I will research the ring test.

[Reed Gray]

They look like the wheels that came on my Rikon 1 hp grinder. They had the epoxy center like that. I have had CBN wheels for many years, and took them off and threw them away. They had so much wobble that I would never even consider using them... A lot of work for those wheels.

robo hippy

[Roger Davis TN]

Hello, I had the same problem. I used a torch, carefully, and melted the centers out. Then I turned new centers out of Osage Orange. The wheels are almost perfect, but still wobble a little, probably due to my ability at accuracy. I wanted to buy the insert centers that Craft Supply sells, but my wheel diameter is not one inch. The vibration is getting better somehow and is acceptable. On my other Rikon the new CBN wheels from Woodturnerwonders are just perfect in rotation balance. I never knew what a sharp gouge was until now. The ribbons coming from the pieces are amazing. Roger Davis.

[Randy McCreight]

It really makes a difference. thanks
Wheels for my 6 inch faster bench grinder have removable plastic cylinders for hubs. They seemed to work ok.

[Randy McCreight]

The ring test seems to be analogous to the difference between a solid baseball bat and cracked bat, or between a cracked slide from Beretta M9 and a good slide. Thanks.

[Roger Davis TN]

Quick note, tightening the wheel to much causes a lot of problems. I just two finger tighten, they will tighten themselves if needed.

[Randy McCreight]

Spoke too soon?
Perhaps I proclaimed my success too soon. I had repaired the hubs of the wheels, which were crumbling, soft epoxy, but I was slow to realize that the wheels were still out of round. I used an inexpensive, hand held dressing tool, which just followed the irregular surface of the wheel. It didn't remove the high spots which effectively formed a shallow, gray groove in the middle of the wheel face. Sharpening was rough: the bowl gouge and scraper just bounced off the irregular surface.
From my experience with a surface grinder and profile grinder for moulding knives, I knew that I needed to hold the diamond dresser securely and feed the wheel gingerly toward the dresser. But how?
I clamped my dressing tool in the tool post of my metal turning lathe, and I turned an axle in the 3-jaw chuck. The wheel was driven by friction between the wheel and the shoulder of the axle. The wheel was held against the axle with the live center in the tail stock.
With some trepidation, wearing a face shield and standing to the side, I made several very light passes of the diamond dresser against the wheel. The friction drive worked, the wheel didn't explode, and the dresser didn't move. Then I made a dozen passes with the power feed, advancing 0.002" for each pass. The gray groove in the wheel gradually diminished! I stopped when the wheel was white and smooth all around. Better than new!
I mounted the wheel in the grinder and sharpened two bowl gouges and my bull nose scraper. The tools did not bounce, and I think the finish is smoother.
I will use them tomorrow to turn the inside of my mesquite bowl.

[Randy McCreight]

After some research online, I found the dressing tool I think will work for me: the Geiger economy model, single diamond tool: <https://www.geigerssolutions.com/Wheel-Truing-and-Dressing.html>

[John K Jordan]

After some research online, I found the dressing tool I think will work for me: the Geiger economy model, single diamond tool: <https://www.geigerssolutions.com/Wheel-Truing-and-Dressing.html>

Randy, I've had one of those for years, very similar except for a second angled guide machined into the other side for a different width tool support. I used it with the Oneway Wolverine platform. (Rarely use it any more with mostly CBN wheels.)

I can recommend it - very effective on both stock and high-quality wheels. The single-point diamond seemed to last forever, far better then some of the other diamond wheel dressers I have.

JKJ

[Randy McCreight]

Thanks. I ordered it yesterday.