Bench Grinder Blues !

[graham-xrf]

I had thought to put this in "Off Topic Discussions", but maybe some good will come of it here.

You know how it is - the not-so-expensive" 6" bench grinder with the reasonably quiet running 375W induction motor you can find in a DIY store on discount day. Clamp to a workmate and watch the whole kit starts to shimmy across the floor. Seems better when up to speed, but goes through a bit of a self-destruct shakeout through a resonance as it slows down.

Mine has always been like that, consigned to fitting on a pointy spiral to spin a buffing calico.

I decide to try again. The spiral pointy will not let go, even I remove it's grub screw altogether. No obvious way to get a grip. Eventually, it, and it's burr on the shaft, are removed. I set up an indicator to check the shaft, and it's perfect! Without wheels, it's absolutely sweet.

The two dished clamp rings, like oversized washers, one with the bigger hole.
What? Place together, and sight up the (slightly mangled) holes that don't seem to have the same centre. Hmm. is this some sort of "rotate one relative to the other" thing? Nah! It's a stamped out thing.

I put the green wheel on the right, because I dropped the left-hand thread nut down there, and I am gonna have to crawl to fish for it with the magnet rod
It runs out madly, but I find a "special spot" where if I keep clamping gently, and bumping it while I turn, I get it to the point I can nip it up not too tight. It won't tighten while holding on to the wheel. It turns the whole motor shaft. OK then. I settle for a short offcut of 15mm copper water pipe, split with hacksaw, and clamped with vise grips onto the motor shaft at the other end. Yay - it runs sweet. no mad vibrations! Trued up with a cheap diamond dresser that looks like the design owes something to the Gillette Razor Blade Company. It grinds on a flea market carbide too, just so nice!

So we get to putting on the other wheel. Left-hand M12 recovered, nothing can be done to get this one to run straight. It sways to left and right like a hula dancer!
Eventually, a "sort of" line up seems to happen, but cannot tighten up even a little without more bumping and washer clamp turning. Nearly there, but now no chance to get a grip on the shaft rotation. The inevitable happens. Grab the green wheel, and try to nip up the grey wheel anti-clockwise - and the nicely set up green wheel comes loose.

I will solve this - even if I have to turn up my own clamp washers, but dang! It shouldn't be this hard to put on a grinding wheel!

 

[tmenyc]

Went through the same issue with my Dewalt bench grinder. It was perpetually unbalanced. I followed the advice here and got a replacement set of hubs and flanges, since those that come with inexpensive grinders have been proven to be garbage. The Raptor set is what I got:

Raptor Grinding Wheel Washers - 2 Pack

With rare exception, today’s bench grinders are supplied with inferior wheel washers that flex or bend easily. Through years of experience, we have found that wheel run-out is nearly always the result of a bent wheel washer caused by over-tightening, rather than a defective wheel.We’ve designed...

www.woodturnerscatalog.com

Then, it was a half hour max to disassemble both wheels, install the new hubs and flanges, dress both wheels, and it has hummed ever since. A key to knowing you're in balance is the at shutoff the grinder takes forever to silently run down. Huge difference.

Good luck!
Tim

 

[C-Bag]

I went with the Oneway balancing setup on my 8” Ryobi after a month of messing about. Pricey but worth it.

https://www.amazon.com/Oneway-2272-Grinding-Balancing-System/dp/B007RPOE4E/ref=sr_1_2?crid=9D0N9YQYC2F5&dchild=1&keywords=grinding+wheel+balancing+kit&qid=1611160015&sprefix=Grinding+wheel+bal%2Caps%2C222&sr=8-2

 

[DavidR8]

@C-Bag I'm interested in that unit to balance the wheel for my surface grinder. Unfortunately it only takes wheels with 1" diameter arbors.
I wonder if bushings could be used to make up the difference.

 

[graham-xrf]

@tmenyc @C-Bag
My thanks Tim & Tony.

The grinder is a 150mm (6"). I am thinking to eventually get a 200mm (8"), about 400W, but I will bide my time, keeping an eye on what's available, and what is quality. For non-critical tool grinding the balance need is not the same as for (say) getting perfection on a surface grinder. That, for me, is an ambition for the future.

The Lick-and-a Promise treatment.
Starting with it poor as it was, I have jiggled it into a state where it does not waggle left to right, and has square dressed up surfaces, and takes a goodly time to spin down. The "motor noise" just might include some sound from bearings, but anyway, the waggle did turn out to be the stamped out wheel clamp "washers". The surface at the hole where it engages the shaft shoulder was "tipped" compared to the outer rim surface, as if one had a shaft in the hole, and yanked sideways. The metal thickness would not allow much fix by way of turning, but I managed to "modify" it back, and file flatter, with a tiny re-face in the lathe. I Just chucked two of them with a 16mm square tool behind as a makeshift parallel and cut back the "high" side a bit near the hole.

The recipe
Very ad-hoc, I know, but when the washer surface is "tipped", there is usually one place, as the washer is rotated, where the wheel is straight. I started with the right side wheel, and it waggled, but if rotated relative to the shaft the washer with it, it finds a place where the run-out seems minimum. Jiggling the shoulder side washer around a bit with a screwdriver, and gentle nip-ups with rotations finds a good place. Then the left side gets it's wheel, and a similar procedure. Nipping up is a progressive affair needing more hands than I have, but it is possible to hold the wheel still with thumb and forefinger, helped by left hand on the other wheel, and pull on the spanner with the remaining fingers - a bit. Checking run-out as we go.

First right side, then move to left side, and nip up anti-clockwise in the same way, helped by a little from holding the other wheel. Then return to the right side, and tighten further. They end up not very tight, just the torque one can get from three fingers on the spanner. This with the wheel gripped between thumb and forefinger, and "helped" a little from grabbing the other side, but not so hard as to have it come undone.

We end up with a reasonably decent running grinder, with both wheels true and dressed, despite the junk that is down there.

 

[graham-xrf]

@C-Bag I'm interested in that unit to balance the wheel for my surface grinder. Unfortunately it only takes wheels with 1" diameter arbors.
I wonder if bushings could be used to make up the difference.

David - check on YouTube. There are great videos on how to get exact dynamic balance for surface grinder wheels. I also mean the ones that do not require one to "drill out little depressions" in the wheel to remove mass and achieve balance.

Also - yes you can use a bushing, they do it all the time

Another real goodie is making up a pair of discs that sit against each other, and mill off one side of each at a little angle. They also get a little hole on the side to stick something into them to allow to turn them relative to each other, and relative to the wheel. Scribe marks on the rims lets you see where they are. The amount of tilt can be set from zero, to some maximum by turning the washer discs relative to each other, and where they act on the wheel is by turning the pair together to cancel the misalignment.

We have had a previous thread on surface grinder wheel balancing. For a fast check, put a drill rod through the wheel and stand it across the lathe prismatic ways, to see if it "rolls" to rest with the off-balance mass at the low point. The test gets more sensitive if you use some V-Blocks to hold a pair of drill rods parallel, and put the wheel shaft across them.

 

[C-Bag]

@C-Bag I'm interested in that unit to balance the wheel for my surface grinder. Unfortunately it only takes wheels with 1" diameter arbors.
I wonder if bushings could be used to make up the difference.

I got onto this setup by watching how you balance a SG wheel on the Tormach. It’s basically the same style of balancing. Personally I find the little inexpensive looking balancer to work perfectly once I soaked the sealed bearing that came with it in acetone to dissolve most of the grease as it causes dampening. I used it also to balance my wheels on my tool grinder in the more trad drilling method. I’m not familiar with the kind of hub your SG uses.

I spent a LOT of time making new hubs etc and unlike the blurb on the another member posted, I got the wheels to turn true and the horrible imbalance was still there. The Oneway fixed it and after resurfacing the wheels and getting a little vibration put it back on the balancer and dialed it right in again. I’m sold, NFI, YADDA YADDA.

 

[C-Bag]

If you look it up there has been several very long threads on how bad the new grinding wheels are now. Even Norton. They are off center, wobbly and seem to have uneven density because even if you get the wobble out and turning true they still vibrate BAD. I contemplated trying to machine the Oneway hubs as they are out of aluminum. At the time several years ago it was beyond my tooling and knowledge. I might have what it takes now but don’t have any need. I justified it that the grinder was around $80, the Oneway was $80. Still less than a Baldor even used and you’d still have a balancing problem with it.

 

[royesses]

Went through the same issue with my Dewalt bench grinder. It was perpetually unbalanced. I followed the advice here and got a replacement set of hubs and flanges, since those that come with inexpensive grinders have been proven to be garbage. The Raptor set is what I got:

Raptor Grinding Wheel Washers - 2 Pack

With rare exception, today’s bench grinders are supplied with inferior wheel washers that flex or bend easily. Through years of experience, we have found that wheel run-out is nearly always the result of a bent wheel washer caused by over-tightening, rather than a defective wheel.We’ve designed...

www.woodturnerscatalog.com

Then, it was a half hour max to disassemble both wheels, install the new hubs and flanges, dress both wheels, and it has hummed ever since. A key to knowing you're in balance is the at shutoff the grinder takes forever to silently run down. Huge difference.

Good luck!
Tim

I made my own washers and bushings and spacers for my 8" Dewalt. I made a diamond tipped truer also. It is now one of my favorite grinders. It did the shimmy shimmy rock and roll when I first bought it. I also replaced the original wheels with some Camel brand brown wheels that trued up very easily.
The washers supplied with cheap grinders are not flat and the bore is out of round. The spacers bore is too large and gets off centered easily. My spacers, bushings and washers fit tight on the shaft. The washers are .250" thick 6061 T65 and the spacers and bushings are 4130.



Roy

 

[Masterjuggler]

I really need to machine a washer with a counterweight balancing system. I turned a combination hub-washer to keep the wheels from wobbling on my bench grinder, but as has been mentioned, the density is all over the place, so my grinder wants to walk across the floor. I usually use it with my foot on the pedestal base and some hearing protection, which is rather ridiculous.

I tried cutting out some lobes from sheet metal, like washers with an offset hole to put behind the nut, but even they haven't been enough to counteract the worst of my wheels.