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mattthemuppet
08-14-2016, 06:52 PM
bought a nice old Craftsman 1/4hp bench grinder the other week to replace my dying a death crappy old grinder. One issue with the old one was that the wire wheel made it vibrate like crazy, so I wanted to try my hand at making auto balancing grinder hubs. I think they came up in engenuity's (?) iPhone vibration detection thread. Idea is to have a channel cut in the face of the arbor which holds some small ball bearings, which then distribute themselves when spun up to balance any imbalances in the wheel.

blank turned down to size and drilled through
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5252_zpsztcnrfht.jpg

reamed to just over 1/2in, face relieved
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5258_zps56zkqflw.jpg

blank parted off
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5259_zpscezt7vsk.jpg

turned around and a groove trepanned into the outside face
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5261_zps3ahcegqf.jpg

mattthemuppet
08-14-2016, 07:01 PM
both outer arbors and their cover plates made
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5262_zps5gs3rxhl.jpg

3/32 balls added (use them on my mountain bike pedals)
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5264_zpsw2jnyexs.jpg

on the stone side
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5265_zpsja81grau.jpg

on the wire wheel side
http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5266_zpso3nefo1a.jpg

first run the grease stopped the balls moving, so I cleaned that out. Second run with 7 balls in each side didn't make any difference to the vibration (the stone didn't need balancing, nice and smooth without any balls). Third run with 25 balls (about 1/2 full) did reduce the vibration somewhat, but not to the level of not having the wire wheel on there. Quality of vibration seems a bit better, the metal tray in the toaster oven next to it didn't resonate any more and it doesn't make that burst of vibration on spin down that it did before.

Not sure why the hubs didn't balance out all the vibration of the wire wheel. Perhaps it was so out of balance that there wasn't enough weight far out enough to cancel it out. Perhaps the principle idea isn't valid. I'm still pleased as punch as my new quiet largely vibration free grinder is now operational.

boslab
08-14-2016, 07:05 PM
I think I'm liking what I think your saying, the physics eludes me, I get a problem with omega in front of things!, but I think your on to somthing there, either it will balance it or throw it completely out I can't decide so please educate me, I'm not getting it
Mark

10KPete
08-14-2016, 07:43 PM
Matt, I saw the same post and have the same issue you do with a wire wheel on one end of a bench grinder. The same grinder I use for lathe tooling..... Need to fix the problem.

Thanks to your 'research' here I'll be using some 3/16 bearing balls to start. You might want to cut the channels bigger and try larger balls to see if that works. Then let us know so I can get it right the first time!!:rolleyes:

Pete

Paul Alciatore
08-14-2016, 08:20 PM
I also am not sure of the physics involved. You say you put enough balls to half fill the channel. Since we are not working from a sound theory or any practical design method, you could just as easily have too many balls as too few. You might try taking some out and see if it is any better.

metalmagpie
08-14-2016, 08:25 PM
I am the guy who posted about self-balancing washers. I believe that they will work well if two things are true. The balls have to be free to move, and they have to have enough mass to correct the imbalance.

The way to think about this is to realize that an imbalanced system will rotate about its center of mass. If the center of mass coincides with the axis of rotation, the system is in balance. If not, it is imbalanced. The heavy end will have a shorter radius of rotation than the light end. The balls move towards the longer radius of rotation. This is how the light end becomes heavier and the system balances.

I agree, Matt, re-cut your groove and use larger balls.

Wire wheels are about the worst case load for a bench grinder. They are never balanced to begin with, and then they start to throw wires and get more imbalanced.

Here is the article I wrote recently on this subject:
http://www.nwnative.us/Grant/shop%20articles/sharpTable/balancing

metalmagpie

Arcane
08-14-2016, 08:51 PM
Matt, I think this has the potential of being a very good commercial product. As it is, balancing a bench grinder is voodoo to many but this unit would put balancing a bench grinder within the capabilities of every owner.

kendall
08-14-2016, 09:16 PM
It works best if the balls are free to move and even bunch up. With tires it works best with BBs because there is tons of room for them to group together. If the balls fit the groove too tightly, they can't bunch up, instead of the required two balls weight at 90 degrees (arbitrary), you end up with 2bw spread between 85 and 95 degrees.
The coarser the balance weight, the least likely it will be to fix a small imbalance. perhaps a mix of large and small weights would work, but I haven't done the math

Dynamic balance works the best with a very small 'grain' size, a ring 1/4 filled with something like mercury or powdered lead in oil (would it 'cake' up?) will work better than 1/4 inch 'balls on a track'.

Edit, this is why the 'water ring' works so well, on washing machines, your 'grain size' is a water molecule. With BBs in a tire, your grain size is 1/1000000 of a tire (total guess)

10KPete
08-14-2016, 09:26 PM
I think metalmagpie is right in that the weights must be able to move freely.

And,

Kendall has the right approach on the weights themselves.

One can buy metal shot in lead, steel, stainless steel, tungsten, and a few other flavors. I would tend to go with the harder shot as it's less likely to deform and clog the channel. But I suspect tungsten shot would be expensive.

Pete

metalmagpie
08-14-2016, 10:00 PM
I think this has the potential of being a very good commercial product.

I'm sure a lot of guys would buy a set of self-balancing washers. But I'm not sure anyone would try to manufacture them without patent protection. And nobody can patent the design because it's already in the public domain.

It's a lot easier to design a really good product than it is to make money selling it.

metalmagpie

J Tiers
08-14-2016, 11:09 PM
I'm sure a lot of guys would buy a set of self-balancing washers. But I'm not sure anyone would try to manufacture them without patent protection. And nobody can patent the design because it's already in the public domain.

It's a lot easier to design a really good product than it is to make money selling it.

metalmagpie

At least they would not get investors without it. Investors love IP But, no doubt, even if some details were patented, the patent trolls would be along before much time has expired, to do a shakedown for as much money as will be very painful, but not quite bankrupting.....

A patent is an excuse for a lawsuit. And most any patent lawsuit will run 2 to 4 million dollars, win or lose.

Get a trademark, or a copyright.

mattthemuppet
08-14-2016, 11:11 PM
I am the guy who posted about self-balancing washers. I believe that they will work well if two things are true. The balls have to be free to move, and they have to have enough mass to correct the imbalance.

The way to think about this is to realize that an imbalanced system will rotate about its center of mass. If the center of mass coincides with the axis of rotation, the system is in balance. If not, it is imbalanced. The heavy end will have a shorter radius of rotation than the light end. The balls move towards the longer radius of rotation. This is how the light end becomes heavier and the system balances.

I agree, Matt, re-cut your groove and use larger balls.

Wire wheels are about the worst case load for a bench grinder. They are never balanced to begin with, and then they start to throw wires and get more imbalanced.

Here is the article I wrote recently on this subject:
http://www.nwnative.us/Grant/shop%20articles/sharpTable/balancing

metalmagpie

phew, I'm happy to have read that explanation. It intuitively made sense beforehand, I just didn't understand why. I didn't realise that you had already done this or I would have a) learned from your experience and b) cited you :) You did a really great write up.

The balls are free to move, you can hear them circulating in the grooves once the grinder is nearly spun down to a stop.

Thank you all for the tips too, they confirmed my thoughts that I didn't have enough mass to balance the imbalances in the wire wheel. Interesting thoughts about the lack of bunching up. I think I'll try cutting the groove wider first, 2x ball width to begin with, to see if that helps. Makes sense that a single width groove won't let enough mass to accumulate at the point of least mass and those balls don't weigh much.

Then if that doesn't work, I'll dig through my ball bearing collection and look to see what I have that's bigger, then cut the groove deeper.

I'll get to it on Tuesday or Wednesday, have a monster bike ride tomorrow which'll completely wipe me out...

edit - I'm sure this would make a neat product, just not by me :) I don't think 2 days per set would earn me much money..

Arcane
08-14-2016, 11:20 PM
Just a reminder Matt, the volume of a sphere goes up as the cube of the radius so a small increase in the diameter of the balls you use makes a significant % increase in their weight.

Regarding production of them, I'm sure the use of a CNC turning center would be the only way to produce them quickly, in volume and at the least cost.

Regardless of that, they are still a heck of a great idea for a home shop machinist and are now on my to-do list.

mattthemuppet
08-14-2016, 11:47 PM
good point, thanks for the tip. I'm limited to how big I can go by the thickness of the arbor (10mm), so the next step up would be good, although I think I only have one of those so I'll order some more.

I'm glad I brought this back up again, even if it's not an especially original idea :) Actually saw something similar demo'ed at a supplier expo in my last job - an auto-balancing bench centrifuge. Sounded pretty awesome, especially as those things get up to 13,000g/ 14,500rpm and students can be really forgetful about balancing them. Actually a grad student in my last lab got kicked out of her previous lab after trashing an ultra high speed centrifuge (40,000rpm) that she didn't balance properly.

these wouldn't take any time to make with a CNC lathe, they're pretty simple. If anyone wants to commercialise them I'd be happy to take my share of the royalties in chocolate :D

ikdor
08-15-2016, 03:08 AM
This is a commercial unit from SKF designed to reduce operator fatigue when using handheld grinders, note that the balls are relatively large. It's partially or fully oil filled, I'm not sure.

http://i964.photobucket.com/albums/ae124/ikdor/Autobalancing.png

flylo
08-15-2016, 09:03 AM
I'd balance it without the wire brush as it may be way off. I posted about prop balancers using mercury & would think a heavy liquid would be the way to go as you'll have no wear as you will with steel balls.

enginuity
08-15-2016, 09:20 AM
Nice work and thanks for posting. Getting your bench grinder balanced really is a home shop requirement, and I think the discussion around it is important and useful.

I've thought a lot about balancing rings since I've balanced my grinder using my smartphone. I've come to a few hypotheses about them:

1. They only work over the resonant frequency, that is the natural frequency has to be lower than the operating frequency of your bench grinder. They only work here because when operating at a frequency ratio greater than one the smaller mass wants to operate 180 degrees away from the system. It is similar in principle to the vibration absorber, but I haven't found the time or ambition to personally go through the math.
2. The reason they aren't used more on bench grinders is because they add cost - a fair bit of machining and such.
3. You really need to quantify the mass you need. You can have too much mass, or not enough. How do you quantify it? (shameless plug: use your cell phone's accelerometer). You can then figure out how much mass you really need to balance your grinder - otherwise you are really guessing.
4. They serve a very distinct purpose. I think the idea is to get the system as balanced as you can and the balance ring is used for the last little bit.


In the end I think they are a good idea if you take the wheels on and off many times. I don't - so I'm not sure if I will make a set up or not. I'm leaning towards making washers with holes around the perimeter to hold the mass and coming up with a quicker way to find the phase but its on my list of things to do and with my grinder running really well right now it will probably wait.

TGTool
08-15-2016, 10:26 AM
One factor governing competition in the marketplace is called barriers-to-entry and a patent is just one of the possible barriers. Others are proprietary processes (not known to the competition) or high cost of equipment. So, for instance, something might not be patented but one producer has figured out how to make it at a competitive price and no one else knows how they do that. Many have run into that in plants where some areas are off limits to visitors or photos prohibited. And one example is the Coca Cola formula which is still secret. No patent, no special equipment for carbonated beverages but no one else can quite match the flavor. (If anyone actually cares that much.)


At least they would not get investors without it. Investors love IP But, no doubt, even if some details were patented, the patent trolls would be along before much time has expired, to do a shakedown for as much money as will be very painful, but not quite bankrupting.....

A patent is an excuse for a lawsuit. And most any patent lawsuit will run 2 to 4 million dollars, win or lose.

Get a trademark, or a copyright.

projectnut
08-15-2016, 12:14 PM
You're employing the same principals used in commercially available car and truck wheel balancers. The major difference is that the wheel balancing units use a fluid to dampen the movement. This company makes them for everything from a motorcycle to an over the road tractor.

http://www.centramatic.com/balancers.rhtml

RB211
08-15-2016, 02:11 PM
Harmonic Balancers?

dave_r
08-15-2016, 02:22 PM
Harmonic Balancers?

No, those are to even out the rotation of the crankshaft, due to short discrete power application to the crankshaft when each piston fires. The crankshaft is balanced separately, so a auto-balancing setup is not be needed (as the crankshaft just needs to be rebalanced if it needs to be reground due to wear).

pinstripe
08-15-2016, 02:52 PM
I can understand the "cost savings" argument for not including these on bench grinders, but why don't manufacturers include these on surface grinders? Would they work well enough for that application?

Norman Bain
08-15-2016, 07:25 PM
My tiny head is saying there should be balls added to be near (or maybe more than) 80% of the groove. This way the balls have more ability to "settle" around the total of the circumference in a more harmonious way.

Less balls seems to me to be asking that they spread out without the assistance of "prior guidance/assistance" from the other balls.

The tidyness (clean arc) of the groove would assist also; else (if not smooth) the balls may stick in what is possibly high spots in the rough surface.

How about a "cup shaped" groove go with grease as the balancing fluid? The shape of the cup such that the grease is spun into the cup. The cover would only be needed to keep it clean.

Norman

Mcgyver
08-15-2016, 08:08 PM
my vote is for leaving the tiny head and balls out of it

metalmagpie
08-15-2016, 09:46 PM
... there should be balls added to be near (or maybe more than) 80% of the groove.

Strongly disagree. As soon as you go past 50% full you start subtracting from your available corrective weight.

Don't worry about evening out the distribution. All of that happens automatically. Really. When my bench grinder (with self-balancing washers) runs, I can hear the balls clicking as they continually adjust themselves in tiny ways. But the grinder runs smooth as silk. Really a joy to use now.

metalmagpie

lakeside53
08-15-2016, 10:10 PM
I can understand the "cost savings" argument for not including these on bench grinders, but why don't manufacturers include these on surface grinders? Would they work well enough for that application?

Because they work fine without them. Much of this approach balancing is fixing inherent problems in the grinder, not just the wheels.

metalmagpie
08-16-2016, 01:14 AM
Because they work fine without them. Much of this approach balancing is fixing inherent problems in the grinder, not just the wheels.

I have proved to myself in the past how much better an import motor can run when its rotor is professionally balanced. I am certain that this would help most bench grinders. At $150 a pop, though, it isn't cost-effective.
Plus, I believe that the upper end import bench grinders (those that cost over $200 new) are balanced better than an import machine tool motor of the same horsepower. Mostly, though, I have run grinders with and without the wheels. Without the wheels they aren't perfectly smooth, but the vibration is minimal and quite acceptable, at least to me (and I'm picky). The problem comes when I install the grinding wheels. I cobbled up a balancing arbor for bench grinding wheels and can prove that many name brand (e.g. Norton) grinding wheels are imbalanced as they come from the factory. Put them on an arbor on a leveled pair of knife edges and they immediately roll, meaning they have a heavy side and a light side. And I also believe that this imbalance is at least one order of magnitude worse than anything inherent to the grinding machine. Meaning, if you fix the wheel imbalance you are likely to get a completely acceptable bench grinder.

metalmagpie

grzdomagala
08-16-2016, 02:13 AM
I saw this system "in miniature" in old cd-drive that i disassembled - couldn't understand what it is, thought bearing somehow lost the balls (grove was filled 25%) :)
Thanks for explanation.

Mcgyver
08-16-2016, 10:11 AM
I am the guy who posted about self-balancing washers. I believe that they will work well if two things are true. The balls have to be free to move, and they have to have enough mass to correct the imbalance.

The way to think about this is to realize that an imbalanced system will rotate about its center of mass. If the center of mass coincides with the axis of rotation, the system is in balance. If not, it is imbalanced. The heavy end will have a shorter radius of rotation than the light end. The balls move towards the longer radius of rotation. This is how the light end becomes heavier and the system balances.



its an interesting subject .....thanks to all for the education.

LKeithR
08-16-2016, 12:56 PM
Because they work fine without them. Much of this approach balancing is fixing inherent problems in the grinder, not just the wheels.

Exactly. Buy a decent, heavy duty grinder and they don't come with built-in issues. Over the years I've run many wire wheels on bench or pedestal grinders--up to 16" dia.--and if the grinder itself has enough mass then balance isn't an issue. I don't think you'll ever get a 1/4 HP grinder to do a good job with a wire wheel.

And how are the bearings in the grinder? I've got a 3/4 HP Dayton bench grinder that must be close to 40 years old. In the last few months it has started to make some noise but I'm sure it's because the bearings are finally starting to go. I've worn out many a wire wheel with it without experiencing balance/vibration problems...

pinstripe
08-16-2016, 01:03 PM
But isn't it standard practice to balance wheels before putting them on a surface grinder? The mass and bearings of the surface grinder will help, but if the wheel had nothing to do with it, then you wouldn't need to balance it. I've never used one, just going off what I have read and seen.

Mcgyver
08-16-2016, 02:12 PM
But isn't it standard practice to balance wheels before putting them on a surface grinder? .

No. It can help chase the perfect finish with a light 6x12, but is not SOP. Cetainly not SOP in industry where they'd tend to have heavier machines. Because of clearance between arbor and wheel, proper was a taper hub mounts, so if you do balance them it will help...but without soft start and stop the jarring action of startup can move the wheel slightly undoing any advantage. SOP is put the wheel on dress and proceed. when quality and quality grinder, even if small, that's all you need most of the time

mattthemuppet
08-17-2016, 01:29 PM
put it some bigger balls yesterday (ahem)

found some 5/32 balls from, I think, an old headset bearing. Cut the groove to ~4x4mm and played around with ball number. 10-15 worked well, reducing the vibration by about 1/3 to 1/2 from the 3/32 bearings and by about 1/2 to 2/3 from no bearings at all. Again, without wheels or with just the grinding stone mounted there was no detectable vibration. Tried more balls - 22 which filled about 1/2 the groove - and there was less reduction in vibration. Fewer than 10 didn't have much detectable effect. 10 =1/4 and 15 = 1/3 full. I could tell that the right no. of balls was doing something also by the difference in pitch - without balls there was a drop in pitch and with the right no. that drop was barely detectable.

So I reckon that 3/16 or even 1/4in balls would be able to balance this out completely. I don't have any 3/16 balls and I'm leery of cutting the groove deep enough for 1/4in balls (the arbor is around 3/8 thick), so I'm calling this good. The vibration is unobtrusive, I've got lots of other projects to do and semester is starting in a couple of weeks (gulp) :)

http://i1349.photobucket.com/albums/p752/mattthemuppet/IMG_5288_zpskztjz5iu.jpg

oh, and I'm confident that this grinder will be enough to turn the wire wheel, I'm not going to be shaping metal with it after all..

BCRider
08-17-2016, 02:15 PM
You need to come up with a Mk II version. The same idea but with a dished out center and thicker rim to allow you to fit a few number of bigger balls. It seems like the performance is leaning to a smaller number of heavier balancing elements. So that's the way you should be considering. And to allow for this it suggests you need a thicker housing. So make it large enough that you can dish the center down so the nut fits into the dished area and make the diameter of the dished area so that it fits the suitable socket to tighten the nut.

I've got a small grinder I keep in the wood working area for touching up chisels and the like. It's always been a real shaker. I'm going to try making one or two of these balancing washers for it.

If you are working with bicycle parts take note that rear wheel bearing balls in most road and mountain bikes that use loose balls are 1/4". Front wheels use 3/16". Most any place that sells bearings will have packs of loose bearing balls in these sizes. They tend to be pretty cheap. And if you work on bikes with Shimano hubs you really should have some of these two sizes around.

plunger
08-17-2016, 02:34 PM
Maybe fill the groove with good old mercury:)

mattthemuppet
08-17-2016, 02:53 PM
I'll add MkII to the project list, projected completion date of August 2018 :) For sure, I think fewer larger balls would be better and hopefully that information will help anyone else who's thinking of making these. I'm happy with it as it is though, especially compared to the pile of worn out junk I had before which required ear protection to use! I do have 1/4in balls for rear hubs, I think I used up my last 3/16s when I serviced my commuter bike earlier this summer - my mtb uses cartridge bearings. I only need to replace the balls every 2 to 3 years so it's not a panic item. I'll pick up some more when I get some spares from the bike shop next time I'm in there, then see if I can work up the gumption to try them out.

mercury would be neat, sealing it in at 3450rpm would be even neater!

Jaakko Fagerlund
08-20-2016, 11:06 AM
No. It can help chase the perfect finish with a light 6x12, but is not SOP. Cetainly not SOP in industry where they'd tend to have heavier machines. Because of clearance between arbor and wheel, proper was a taper hub mounts, so if you do balance them it will help...but without soft start and stop the jarring action of startup can move the wheel slightly undoing any advantage. SOP is put the wheel on dress and proceed. when quality and quality grinder, even if small, that's all you need most of the time
The wheels on a surface grinder are definately balanced as SOP in industry and especially on larger machines as the wheels get really heavy. A balanced wheel lasts far longer between sharpenings and leaves better surface finish.

Mcgyver
08-20-2016, 12:44 PM
The wheels on a surface grinder are definitely balanced as SOP in industry and especially on larger machines as the wheels get really heavy. A balanced wheel lasts far longer between sharpenings and leaves better surface finish.

I'll concede my remark was two inclusive, "industry" covers a lot of ground. To be more exact, I do not believe it is common or necessary with most tool room/commercial machinists grinders and required finishes. I sometimes do so with my my Norton 6x12 and it can have an affect on finish, but even on such a light grinder its not great. I suppose neither of us have been in every shop on planet, but I never seen it or had a commercial guy tell the do so. I've asked many about it as subject is of interest as I became quite interested in getting the best finish out my small grinder.

Jaakko Fagerlund
08-21-2016, 05:42 AM
I'll concede my remark was two inclusive, "industry" covers a lot of ground. To be more exact, I do not believe it is common or necessary with most tool room/commercial machinists grinders and required finishes. I sometimes do so with my my Norton 6x12 and it can have an affect on finish, but even on such a light grinder its not great. I suppose neither of us have been in every shop on planet, but I never seen it or had a commercial guy tell the do so. I've asked many about it as subject is of interest as I became quite interested in getting the best finish out my small grinder.
On a small grinder (7" wheel or so that is 1" wide) the effect isn't very dramatic, but for example our bigger Jakobsen with a 400 mm wheel that is 75 mm wide it really has an impact to balance it, not only for keeping the wheel in good shape for long and to get a good finish, but for bearings sake also.

Very true that we haven't been in every shop on the planet, but the three toolrooms I know will balance the wheels (even smaller ones) and my friend works on huge grinders in a machine shop that produces stuff for ships and they just have to be balanced or there will be a catastropic wheel failure.

mattthemuppet
09-18-2016, 03:18 PM
quick update. Finally got some time to recut the groove for 3/16 balls and I made it wide enough that the balls could stack in one spot (in a zig zag pattern). Filled the groove a 1/3 full, spun it up without and then with the wire wheel. Still some vibration and no detectable difference from the 5/32 balls, but a noticeable difference from no balls. That'll have to do, works well and what vibration there is doesn't affect the finish I get from the grinding wheel.

My guess is that it's just a crappy wire wheel - got it from Lowes and the hub is visibly out of round with respect to the center hole. I'll keep my ears and eyes open for a better one at some point.

oldtiffie
09-20-2016, 12:59 AM
Why not get/buy a good angle grinder and fit wire brushes and "flap" wheels as required?

https://www.google.com.au/search?q=michell+bearings&rls=com.microsoft:en-AU:IE-SearchBox&rlz=1I7IRFC_enAU360&biw=1280&bih=585&source=lnms&sa=X&ved=0ahUKEwj0vajVkJ3PAhWCsJQKHRhMBqUQ_AUIBSgA&dpr=1.5#q=flap+wheel

https://www.google.com.au/search?q=flap+wheel&rls=com.microsoft:en-AU:IE-SearchBox&rlz=1I7IRFC_enAU360&biw=1280&bih=585&source=lnms&tbm=isch&sa=X&sqi=2&ved=0ahUKEwjprdG0lJ3PAhWJHJQKHXo1BsMQ_AUIBigB

mattthemuppet
09-20-2016, 12:42 PM
that's another good option and something to think about when I set up shop permanently, for now this is convenient especially for small pieces like drill chucks.

BCRider
09-20-2016, 12:55 PM
Why not get/buy a good angle grinder and fit wire brushes and "flap" wheels as required?

https://www.google.com.au/search?q=michell+bearings&rls=com.microsoft:en-AU:IE-SearchBox&rlz=1I7IRFC_enAU360&biw=1280&bih=585&source=lnms&sa=X&ved=0ahUKEwj0vajVkJ3PAhWCsJQKHRhMBqUQ_AUIBSgA&dpr=1.5#q=flap+wheel

https://www.google.com.au/search?q=flap+wheel&rls=com.microsoft:en-AU:IE-SearchBox&rlz=1I7IRFC_enAU360&biw=1280&bih=585&source=lnms&tbm=isch&sa=X&sqi=2&ved=0ahUKEwjprdG0lJ3PAhWJHJQKHXo1BsMQ_AUIBigB

Because often the part being worked on needs both hands to hold it securely?

The correct answer is "yes" to the idea of having both fixed grinders that can be fitted with wire wheels as well as angle grinders for items that are large and heavy enough to sit still or which can be held in a vise.

im#2
09-20-2016, 06:50 PM
I'm glad this has come up as I'm building a lunch bucket thickness planer blade sharpener for a machine that has become "obsolete", out of a radial arm saw and was just considering how to get the lineal accuracy I need to do this and this balance thing is one of the things I was mulling. Thanks for the great education this site gives us! Any helpful discussion would be appreciated

JoeLee
09-20-2016, 11:35 PM
Maybe fill the groove with good old mercury:)I had mentioned using mercury in the thread I had going on balancing grinding wheels.
You wouldn't need to put oil in the groove to dampen any vibration because the merc would act as a dampener as well as the counter weight. I think it would be a matter of weather or not you have the right amount of merc in the grove to compensate for the out of balance wheel.

JL................

Black Forest
01-04-2017, 09:45 AM
I use wire wheels in my drill press when I need both hands to hold the part. I have several that I keep right next to the drill press. Mostly I use them for cleaning threads on rusty bolts.

DR
01-04-2017, 01:29 PM
I can understand the "cost savings" argument for not including these on bench grinders, but why don't manufacturers include these on surface grinders? Would they work well enough for that application?

Surface grinder wheels are mounted on hubs with an internal female taper. That taper in turn mounts to a male taper on the grinder spindle. In theory once a wheel and hub are in balance it can be removed and then remounted without re-balancing.

Surface grinder wheel hubs sometimes have adjustable weights used to aid in the balance of the wheel hub combination. My surface grinder using 7" wheels does not have adjustable weights in the wheel hubs, but those are relatively light wheels so any imbalance can easily be corrected by dressing the wheels..