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Balanced Grinder Hubs

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Ray C

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Several people are getting into surface grinders so, I'll post some experiences with making a balancing grinder hub. Even though I haven't finished the turret tailstock, I'll start posting some of the photos of prior work so interested folks can get a move on it.

It's more tricky than you might imagine and I had to screw it up 2 times before finding the right sequence of operations for it to come out properly. An experience machinist might have less problems and I'm open to suggestions. The critical part is concentricity of the tapered bore WRT the outer spindle diameter that the wheel goes onto. The taper angle must be perfect -no room for error and if that concentricity is not within +/- 0.00025, there's no hope for it for precision grinding. Mark it and only use it for coarse grinding. The wheel cylinder part must be 1.2495 +0.0003 -0.0000. The backing plates can be off a little (+/- a thou) because the buffer pads will absorb the error.

Here are some starter photos and explanations.

Here's a finished product that is not yet heat treated but is otherwise finished. I've been using it for a few months now. Shown is the backside with the dual balancing weights. Those weights must be secured properly and the circular groove must have adequate depth to ensure a good fit. CAUTION: Never use any grinding wheel without a safety cover. My safety cover is home made and has a front door that covers the front of the wheel. -And for the record, the balancing mechanism here is nothing new; this design has been around for many years. Although you can't see it in the photo, there is a circumferential groove that the cap screw fits into to aid secure attachment. Also shown is the locking nut as well as a view of a mounted wheel. Of course, you'll need to make a spanner wrench. -And don't forget to use all left-hand threads if your machine spins in the clockwise direction while facing it from the front.

Backside Balancers.JPGLocking Nut.JPGMounted Wheel 1.JPG

The wheel must be balanced prior to spin-up. You'll need to make an off-site balancing arbor and balancing apparatus such as this. It mimics the SG spindle shaft. This is one of those projects where you need to make a lot of parts just to make the part... Anyhow, you mount a wheel on the hub without the balancing weights, put it on the balancing apparatus, find the heavy side and place the weights equally on the opposite side of the heavy end. The balancing weights are just some milled pieces of metal with a cap screw.

Balancer Arbor.JPG TaperedShaft-Jig.JPG

Here's a raw hub. I make them from two pieces to save materials and a lot of swarf clean-up. It's 1045 and was welded in the raw HR condition then, fully stress relieved and soft annealed. When it comes time to lathe these down to size, those weld caps will come off like butter.

Raw 1.JPGRaw 2.JPG

Here's a piece of O1 heat treated to 60 RC and was my attempt at making a parallel bar. It's pretty good and I use it a lot for different things. If the SG hub is not perfect, every wobble it induces in the wheel will show-up in the grind piece. This particular grind came-out OK. I'm still practicing and teaching myself how to use a grinder. There is almost no information out there on how to use one...

photo.JPG

OK, that's it for now. We'll pick-up on this later. I'll cover the sequence of operations starting from the raw hubs and will also include how I made a taper reamer.

Ray

Backside Balancers.JPG Balancer Arbor.JPG Locking Nut.JPG Mounted Wheel 1.JPG photo.JPG Raw 1.JPG Raw 2.JPG TaperedShaft-Jig.JPG
 

samthedog

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Thanks for the excellent post Ray. I know it's a bit of a thick question but are the balancing weights visible in the first picture? I am not sure what they look like at all as I am new to this whole grinding thing. Thanks again for taking the time to put this up and help us neophytes out.

Paul.
 

Ray C

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Yes, in the very first picture, look at the two "ears things" that are held down with cap screws. Those are the balancing weights and are located on the backside of the hub. You start-out by mounting the wheel on the hub without the weights then, put it on the stand-alone balance unit to find the heavy side of the wheel. Then, the balance weights are placed on the opposite side of the heavy part of the wheel. You cannot use just one balance weight as, it would have to match exactly how much the wheel is off balance therefore, you use two balance weights which makes a triangle. A triangle of weights can be balanced without the need to exactly match the amount of counter balance. When this wheel runs, you only hear it. You don't feel it. If you move one of those weights a tiny bit, you can feel it. If you can feel it, it will show-up in your grind.

Some words of caution: These things are not toys and those spinning weights must be attached securely. Once again, this design is very old and till this day, there are commercial balancing hubs which work exactly like this. It is not a new idea.

BTW: I completely understand the dangerous nature of grinding wheels and it's a touchy topic. If the other mods wish to cancel this thread and delete, there will be no fuss from me. I did this project a long time ago and did not post it due to serious nature of this kind of work.

Ray




Thanks for the excellent post Ray. I know it's a bit of a thick question but are the balancing weights visible in the first picture? I am not sure what they look like at all as I am new to this whole grinding thing. Thanks again for taking the time to put this up and help us neophytes out.

Paul.
 
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bcall2043

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Several people are getting into surface grinders so, I'll post some experiences with making a balancing grinder hub........................................................

Ray
Ray,

Thanks for posting this project. Charley Davidson and I have one surface grinder wheel adapter between us. We were just today discussing trying to make some more adapters since they are so expensive. We will be eagerly watching your post to learn your experiences.

We were also discussing making the install and removal tools. Have you also made your own tools? I have the pattern adaptor and Charley has the pattern tooling. We both need the knowledge from your experience.

Benny
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Ray C

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I have yet to come across a wheel that balances well even after truing it up. The wheel shown is a Norton costing over $120. It does not self-balance. I have a dozen or more ranging in price from 30 to $150. The only ones that self balance (only 2) are 3/8" wide and 6" diameter. I prefer 7 and 8" wheels as they last longer and with VFD, can spin them down to get the SFM right.

I had two wheels that were $50 each (from MSC) one was so out of balance, it blew up inside the 1 minute spin-up. The other was so bad, it would not balance even with this setup so, I took a hammer to it and thew it in the trash. MSC would not take a refund BTW...

If you come across a brand that's affordable and self balances, let me know please -and I'm not kidding about that.


Ray



Excellent post Ray and I thank you for it and eagerly await the next installments.

While talking to the guys at Sopko and especially to David Haviland (GREAT guy) at Precision Spindle up in Ontario they both led me to believe that balancing weights are not a necessity and are really more trouble than they're worth if you don't keep an adapter in each wheel you have.
They said that especially in the 8" and under sizes that a quality wheel will be balanced very closely and that dressing it will make it about perfect.

Again, Thank you for this great thread!
- - - Updated - - -

I have yet to come across a wheel that balances well even after truing it up. The wheel shown is a Norton costing over $120. It does not self-balance. I have a dozen or more ranging in price from 30 to $150. The only ones that self balance (only 2) are 3/8" wide and 6" diameter. I prefer 7 and 8" wheels as they last longer and with VFD, can spin them down to get the SFM right.

I had two wheels that were $50 each (from MSC) one was so out of balance, it blew up inside the 1 minute spin-up. The other was so bad, it would not balance even with this setup so, I took a hammer to it and thew it in the trash. MSC would not take a refund BTW...

If you come across a brand that's affordable and self balances, let me know please -and I'm not kidding about that.


Ray
EDIT: My plan here is to have a hub for each of the wheels. Also, these hubs can be removed from the SG w/o upsetting the balance. I can reinstall a wheel and run it.
 

Ray C

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Benny,

The only tools I've made are the hubs, the various spacer rings, locking collar and locking nut. Also some spanner wrenches and a device that looks a little like a ball-joint separator to get a hub off the spindle. It's not good to grab a wheel by the sides and yank it off.

I do not understand what you mean by the pattern adapter. If you hum a few bars, I'll try to whistle along. I can post a CAD drawing of this design but, I have since modified a few of the dimensions and the print is slightly out of date. -Probably doesn't make a difference as I'm assuming your spindle has different dimensions and backside clearances anyhow. I'll gladly post the CAD drawing if you want it.

Ray


Ray,

Thanks for posting this project. Charley Davidson and I have one surface grinder wheel adapter between us. We were just today discussing trying to make some more adapters since they are so expensive. We will be eagerly watching your post to learn your experiences.

We were also discussing making the install and removal tools. Have you also made your own tools? I have the pattern adaptor and Charley has the pattern tooling. We both need the knowledge from your experience.

Benny
The Orphanage Never Closes
 

samthedog

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Ray, the funny thing is that despite buying my grinder completely tooled up and with all the accessories, I don't have a single balancing hub. I have 17 hubs that came with the machine yet none that have a balancing mechanism. It came with a bunch of wheels that seem to be high quality that are a mix of German, Swedish and Danish origin. I will make a balancing stand and see how they look,

On a side note, I did get a few pulley wheels and am inclined to spin the wheels below their rated speed to ensure I am keeping things safe. The machine terrifies me and I understand your hesitation to post your work up. My uncle was hit by a wheel that flew apart and had an artery severed. If not for my other uncle visiting on the off chance he would have bled out in his shop. I cannot stress the need to work smart and safely enough with these machines.

Paul.
 

george wilson

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I recommend trading those socket head cap screws for set screws. The SHCS's stick out too far and set screws won't,making it possible to grind things that the socket heads might accidentally strike.
 

Ray C

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I totally agree and as a matter of fact, I want to design a much less obtrusive weight to hang on there. The ones I made were quickies just to see if the darn thing worked or not.

I concur... Safety can be augmented with better design here. -And I will do it.


Ray


I recommend trading those socket head cap screws for set screws. The SHCS's stick out too far and set screws won't,making it possible to grind things that the socket heads might accidentally strike.
 

eightball

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Ray, when i used to grind paper machine rolls, We balanced all our wheels. Mind you these were 30 inch wheels 4 inches wide. Anyways , we made our own balance weights. Our mandrells had a groove around them for the weights. the edges of the groove were tapered, like a dovetail. so when you tightened the weights they locked against the taper. Im hoping this makes sence. We would machine a piece in the lathe the same diameter as the groove in the mandrel with the same angles on it. then we would lay out the individual weights around this circle and cut them out. so now we had about 16 to possibly 24 balance weights. we would put match marks on every weight, then drill them for a set screw. Then we cut them diagonally right across the set screw hole. so now they look like two wedges.you would slip each side in the grooove on the mandrel and line up the two halve of the set screw hole and put your set screw in as you tightened. it wedged itself in . i made these weights out of brass or bronze usally. so i never had any issues getting the set screws out later. i also used a very good scale and balanced the weights so they all weighed the same. When i balanced i would find the heavy spot and put one weight exactly opposite it. For explanations sake we will call where that weight is 0 degrees. Then i put a weight at 90degrees and another at 270. i would then move these 2 weights together to acheive balance. I hope i havent confused you, but i ground rolls for over 10 years and i balanced alot of wheels. These weights fit inside the balance groove and nothing protruded out. If your making your own mandrels. you just have to bevel those edges of the groove after trepanning it out. Hope this makes sence, If i was currently working id just take a pic and it would be self expanitory.But im currently out receiving radiation treatments and facing surgery, so it will be a while b4 i go back to work. If my explanation is unclear i may could draw a pic. Also Ray, I would balance a wheel, mount it on the grinder and dress it,Then take it back off and balance it again. My coworkers dressed the wheel then balanced it. they didnt balance it first. these were very good quality wheels Nortons and pacers mostly but i never like putting an un balanced wheel on the grinder even though truing it up does change the balance a little.
 

bcall2043

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Benny,

.............................. I do not understand what you mean by the pattern adapter. If you hum a few bars, I'll try to whistle along............... I'll gladly post the CAD drawing if you want it.
Ray
What I meant by "pattern adapter" was since we had no drawing or knowledge of what an adapter dimensions should be we would use the one existing adapter on my surface grinder as a pattern to "reverse engineer" and make additional adapters. A drawing with real dimensions and tolerances would be nice. Likewise, Charley has a fairly complete set of tools for install and removal of grinding wheels that we could copy to make additional tools for me since no tools came with my surface grinder.

Benny
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benmychree

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For grinder acessories such as wheel hubs and high speed belts, look up the William Sopko Company; they have adaptor hubs for a number of makes of small surface grinders and tool & cutter grinders.
 

Ray C

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Yes, Sopko seems like the go-to place for grinder stuff but there's one small problem... I called them three years ago when I got my SG and the balancing grinder hubs were running about $800 each. -Ouch! I'd like to have about four units as that's how many wheels I do most of my work with. This is probably the one time in my life when I'm making something that will be cheaper than purchasing it...

Ray


For grinder acessories such as wheel hubs and high speed belts, look up the William Sopko Company; they have adaptor hubs for a number of makes of small surface grinders and tool & cutter grinders.
 

eightball

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IMG_0073[1].JPGjust a rough sketch of what my weights look like, being tapered, if they werent split , you couldnt get them inside the groove. The taper wasnt that much, im thinking it was about 15 degrees but its been over 10 years since i ground rolls so im not sure

IMG_0073[1].JPG
 

Ray C

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The thread about B&S taper reamers (http://www.hobby-machinist.com/showthread.php/17915-Brown-and-Sharpe-Taper-Reamer-Straight-shaft-w-o-spinning-between-centers) has come to a close. The purpose of the reamer was to complete these balanced grinder hubs and we're in a position to resume... You might want to look at the first few posts of this thread to refresh your memory.

When making these, it's important to plan the sequence of operations. I'm going to do all the backside work first and have chosen the rear face as the starting geometry. There is plenty of meat on the blank part so there's plenty of room to bring all the other dimensions in line.

First, the piece is propped with parallels to give a little clearance to face the back. Always remember to remove the parallels before spinning-up. A base hole is drilled all the way through as a starting point for the taper cut. The material is 1045 and it's already been fully normalized. It's very easy and nice to work with and the ER80s welds caps came right off.

CS1.JPGCS2.JPG

Next, the taper is cut by critically setting the compound angle and using only compound travel to move the boring bar. I've shown many times how to use DIs and make Rise over Run setups and this is how the angle of 7.125[SUP]o[/SUP] was set here. If you need help with that, let me know and we'll go over it more closely.

The cross slide is moved back to take 15 thou DoCs until the backside diameter is just shy of one inch. I stopped at roughly 0.995". It's hard to make that measurement since there's no real lip but, in this case, close enough is good enough. The depth of the taper is predefined by geometry and I keep pushing in until it stops cutting. Remember to lock the compound and disable any possibility of engaging autofeed. This is close work to the chuck and you'll crash in a heartbeat. BTW: I used the "outside" jaws because the other set would not allow me to insert the stub part of the hub in the chuck bore.

CS3.JPGCS5.JPG

A groove is needed to accommodate some balance weights. I don't use this groover often but it's handy. It needs a new carbide insert and I can't seem to locate one. Any clues folks on where to get them? Anyhow, I'll be making many of these (4 more) so, the groove will be uniformly placed on all units.

CS6.JPG


Safety note: In this procedure, the lathe safety is engaged and the unit is powered off. I think you know why.

The taper reamer that was just made earlier is inserted, light pressure from the tailstock is applied and it's manually cut. Happy to report, the cutter went through the metal like butter. Nice even swarf piled up in the flutes. I realize now though, I should cut the flutes about 20 thou deeper as the cutter would quickly pack up and need to be wiped clean. (and yes, that's a bad angle on my wrist but I was forced into that because I can't put too much pressure on the fingertips yet).

The taper came out very nice and the ending hole size is about dead on at 1" -which is what is needed for the arbor on my particular surface grinder.

CS8.JPGCS9.JPG

More later

Ray

CS1.JPG CS2.JPG CS3.JPG CS5.JPG CS6.JPG CS8.JPG CS9.JPG
 

Ray C

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OK, here's the finished hub. To finish it, the special spindle was made (quite some time ago) to mount the hub then, you keep carving away until all the exterior dimensions are met -except, I leave about 0.002" (1.252" Dia) on the shaft diameter where the wheel sits. Cut the threads to the appropriate size (1.25" x 18 TPI-LH). The spindle must be mounted carefully and run true. Although not shown in the picture, there's a center hole in the end of the shaft which was supported by a live center while all the external dimensions were cut. After the threads are cut, it's checked on the grinder.

This one is running very true but I can indeed feel the slightest bit of vibration. -No worries... The part will be heat treated and when it's done, the inner taper will be touched-up with the reamer and then, it will be mounted on the actual surface grinder, spun up to about 1000 RPM and with a tool holder mounted on the mag base, I'll trim that last 0.002" off.

I know this sounds a little crazy but, I've made a few of these things before and if it's not done in the proper sequence, you'll stand little chance of the final product spinning perfectly. I have done it before without finishing it on the actual grinder but, it takes a LOT of setup time. This is a shortcut that works very well.

BTW, if you purchase these brand new, they cost a fortune (Sopko wants about $800 for them).

Surface grinding with a perfectly balanced wheel is like the difference between night and day...


SA1.JPGSA2.JPG

Ray

SA1.JPG SA2.JPG
 

mattthemuppet2

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a bit off topic (beautiful machine work by the way), but has anyone thought about making an auto-balancing hub? They make them for Nascar and for high speed centrifuges (13,000rpm+). The basic premise (I think) is that there is a cavity inside the hub that's has a number of small ball bearings loose in it. When the hub (or rotor in the centrifuge) spins up, these are supposed to distribute themselves around the inside of the hub to balance it. I saw one of the centrifuges in action and it was seriously impressive.

That's about all I can contribute though as I'm not much of an engineer!
 

Ray C

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I've heard of systems similar to this that worked with mercury instead of ball bearings. It's intriguing indeed and seems (at the surface) easy to build but, sometimes things are deceivingly difficult.

I'll let you know what I come up with...

Ray



a bit off topic (beautiful machine work by the way), but has anyone thought about making an auto-balancing hub? They make them for Nascar and for high speed centrifuges (13,000rpm+). The basic premise (I think) is that there is a cavity inside the hub that's has a number of small ball bearings loose in it. When the hub (or rotor in the centrifuge) spins up, these are supposed to distribute themselves around the inside of the hub to balance it. I saw one of the centrifuges in action and it was seriously impressive.

That's about all I can contribute though as I'm not much of an engineer!
 

mattthemuppet2

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I've heard of systems similar to this that worked with mercury instead of ball bearings. It's intriguing indeed and seems (at the surface) easy to build but, sometimes things are deceivingly difficult.

I'll let you know what I come up with...

Ray
yeah, simple ideas and simple implementation = already done :)

Presumably you'd need a balancing material that has a fine enough resolution to counteract all of the imbalances in the wheel, yet moves freely enough to not clump or introduce its own imbalances. I guess it also depends on the inside diameter of the hub too. You can get really tiny ball bearings though. I can't remember the size of the ones in my mtb pedals, less than 1/8in for sure, but something along those lines might be an option. Wouldn't really want to work with that volume of liquid mercury to be honest!

here are some links I found, not all of which may be useful:
http://www.medicalautomation.org/2010/07/self-balancing-centrifuge-rotor/
http://www.google.com/patents/US4412831
http://www.google.com/patents/US3692236
http://www.innovativebalancing.com/index.php
 

Ray C

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Oh for sure... I wouldn't mess around with mercury. Ball bearings would probably be the way to go. I agree, the issue is allowing them to self-distribute without getting jammed or stuck together. -A very solvable problem. Also, you'd need to have enough mass of BBs to effectively counter-balance the wheel's imbalance given the rotational momentum needed at a fixed radius. -Also a solvable problem.

Thanks for the links... I'll look them over.

Ray


yeah, simple ideas and simple implementation = already done :)

Presumably you'd need a balancing material that has a fine enough resolution to counteract all of the imbalances in the wheel, yet moves freely enough to not clump or introduce its own imbalances. I guess it also depends on the inside diameter of the hub too. You can get really tiny ball bearings though. I can't remember the size of the ones in my mtb pedals, less than 1/8in for sure, but something along those lines might be an option. Wouldn't really want to work with that volume of liquid mercury to be honest!

here are some links I found, not all of which may be useful:
http://www.medicalautomation.org/2010/07/self-balancing-centrifuge-rotor/
http://www.google.com/patents/US4412831
http://www.google.com/patents/US3692236
http://www.innovativebalancing.com/index.php
 

mattthemuppet2

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I seem to remember reading about a spray on coating that makes things ever so slightly -vely charged and helps stop them sticking together, which might be one approach. The actual physics and maths of how many and so on I wouldn't have a clue about, I just like neat ideas :)

the other ideas such as shifting the center of rotation to balance might not be much use for a grinder where the wheel has to stay a fixed distance from the table. I wish I was able to find more about the ball bearing self balancing centrifuge rotors, pretty sure they're made by Beckman Coultier (sp?). It was fun deliberately going against everything I've been taught and not balancing the rotor and it still working fine.
 

benmychree

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The bottom line here, is for ordinary work, with wheels less than 7" diameter, that are made in USA, no special balancing will be necessary; it is a souution in search of a problem.
 

mattthemuppet2

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could be, I'm not experienced enough to say one way or another, but it is an interesting solution without doubt :)
 

Ray C

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The bottom line here, is for ordinary work, with wheels less than 7" diameter, that are made in USA, no special balancing will be necessary; it is a souution in search of a problem.
I totally disagree... My Made in USA Norton wheels (all 5 of them costing between $60 and $75 each) don't balance worth a darn. Matter of fact, the only wheels that balance half-way decent are some no-name import 3/8" or 1/2" wide -and even those require balance weights if you want to fine-tune the cupping out of the finish... And BTW, they were purchased from MSC. One of them was so bad, not even the balance mechanism could make it run right and MSC will not refund or exchange grinder wheels...


Ray
 

itsme_Bernie

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Wow, no kidding...
I am definitely working toward surface grinding... But I will have some homework to do to really get it going!


Bernie
 

Senna

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I'll merely add what Brown & Sharpe says in their B&S 13 grinder manual about wheel balancing 7" and smaller wheels.
They clearly state that balancing such wheels is unnecessary and unproductive.

I have a balancing stand and arbor ( I presume it's still fine after the fire considering its placement in the garage) but I intend to use it for only my 10" grinding wheels. I'll check the small wheels for balance but, heeding the advise from B&S, will not rush to purchase balancing adapters for them.
 

benmychree

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I am on record as not being concerned with balancing small grinding wheels, as defined by the 7" diameter line drawn in the sand; having said this, I relate that a couple of months ago, I bought a lot of B&S type hubs on E Bay, and to my surprise, one of them was a Sopko balancing hub; so far I have not been tempted to use it, still not seeing the necessity for doing so, being as the MicroMaster seems to do a job that is adequate for the work I put it to, in fact, it does a quite nice job (it's good enough for the gals that I go out with, anyway). Having said this, I posit that there may be a guy out there that needs it more than I do, and accordingly, I invite offers; it looks to be in excellent condition, possibly unused.
 
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