auto-balancing bench grinder arbors

[Scrounga]

Good idea but I just balanced the wire wheels. I made a simple jig and use short self tappers to counter balance a bit like the way they used to do car wheels.
Stopped nearly all the vibration which used to drive me crazy. Nice work you have done there. Cheers Stuart, Australia.

[tonyfoale]

I have not read all the follow up posts here so I hope that I am not being repetitious.
Decades back I had access to mercury and I made similar devices using mercury instead of balls. Years later after some house moves , new grinders and the loss of the mercury source I tried the same with water. That only worked when I made them with impractically large diameters.
This theme has prompted me to revisit this. A month or two ago I wanted some hard and heavy balls and I bought a box of 1/4" tungsten carbide balls. They were not expensive and should be better for this application. In fact when I finish writing this I'll be in the workshop making one from a Delrin case for low friction and carbide balls for their mass. Also their greater mass to size ratio should reduce any sticking problems. Lead balls might work but I doubt that they would retain their shape over time and start sticking. Delrin might suffer a similar fate over time from brinelling by the carbide balls. If so then I will change to metal cases.

PS. I'll do this with a square groove about 1 mm wider than the ball diameter. The balls will only contact the holder on the outer part of the groove when in use so plenty of clearance on the inner wall will do no harm unless it is so big that the balls jam under one another.
I'll report back.

PPS. I have already changed my mind. I will go for steel cases and forget the Delrin.

[piper184]

Suggestion: Use a larger quantity of smaller diameter balls. Lead shot comes to mind as well as ceramic balancing beads used for tire balancing. The ceramic beads can be had in as small as 1oz. bags online or at a lot of automotive parts stores. They are heavy for their diameter and "flow" easily. I have been using them for years in my motorcycle and car tires with great results. The farther away from the shaft the more effective they are. Don't use lubrication as it will cause the beads to clump together.

[tonyfoale]

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[Hopefuldave]

Thanks for the write-up gents!

Tony: Where did you find "affordable" carbide balls? I've been looking and they'd cost more than the grinder I have... (which does a natty rumba across the bench).
Also, the case looks pretty easy to 3D print, I may have a go at that!

Dave H. (the other one)

[tonyfoale]

Thanks for the write-up gents!

Tony: Where did you find "affordable" carbide balls? I've been looking and they'd cost more than the grinder I have... (which does a natty rumba across the bench).
Also, the case looks pretty easy to 3D print, I may have a go at that!

Dave H. (the other one)

Try https://www.acerracing.com they also have a presence on Amazon and eBay. Good luck. IIRC I bought a pack of 10 1/4" balls, I think that they were around US$15.
I actually bought the balls to use in a Leeb style hardness tester that I built. However, I found that steel balls worked better in that application.

Click pix for full size

[Toolmaker51]

still a bit of a work in progress, but I made these in the hope of balancing a wire wheel which is causing my grinder to vibrate.

Idea is to have a groove in which some ball bearings are free to rotate and come to rest at the point of lowest effective mass on the wheel, thus balancing it. Well, that's the idea anyway, not quite there yet.

.......reamed to 0.501 or so, slip fit on the arbor. Face relieved...it only contacts the wheel at its periphery. Not 100% sure why this is necessary, but that's how the original ones are made so..
Attachment 13074

Relieved drive washers, aren't exactly a requirement to run a wheel, it's a function of manufacturing process in conventional lathe work.
CNC programming compensates for the differing by Feed Rate Per Revolution from the lesser at larger diameter, to increase at center; though facing typically moves outboard.
Conventional lathe cross slides driven by feed screw have a continual rate regardless face diameter.
The .00X per revolution rate nearer center causes a slightly raised profile. Trepanning a depression keeps that interference from outer portion of washer and blotter. Likewise, cast washers streamline facing process by incorporating that feature in the mold pattern. Many machine pads have that, most floors aren't so flat.
Broad contact doesn't assure stability.