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Thread: Thoughts on grinder vibration

  1. #1
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    Default Thoughts on grinder vibration

    Hi:

    I thought Id post this in the turning forum rather than power tools as it seems to me nobody needs a well behaved grinder more than a turner.

    What a PITA to get the vibration down on my 8 inch grinder. The grinder sounded like an aircraft, so I knew things were really bad in the balance department. I had a coarse OEM stone on the left side and the Norton white on the right. I wanted to move the white to the left side and mount my Norton blue on the right. I removed both stones and began playing with the white stone on the left side. I finally got lucky and obtained a reasonably low vibration. I do mean lucky, there was nothing deterministic in what I did that could be repeated to obtain the same result again. In fact, the Norton blue is not mounted because I couldn't get lucky twice.

    There is a tendency for severe and highly variable sideways wobble. I think most of the problem pertains to two issues. Firstly, the bushing plastic pieces that allows one to mount to a 1, 3/4 or 5/8 inches shaft have way to much slop. This arrangement must have at least 10 thou movement if not more. The second weak spot looks like the side washers (flanges?). I think they could be flattened and probably larger diameter too. In fact, at one point I mounted my 5 inch saw blade stiffeners (LV 16T01.02) and things looked much better, but they were rubbing against the shield a bit and I was worried about squeezing directly on the stones as opposed to the cardboard the OEM washers bear down upon.

    For those whom are unfamiliar with the LV saw blade stiffeners, see below.

    grinder 009.jpg

    When I get a metal lathe working again, I am going to machine a proper bushing for the centre hole, including reaming the 5/8 diameter, and maybe even making some big washers if I dont in the mean time buy a 3 inch set of stiffeners at LV for the purpose. Or maybe the bushings exist as a commercial product. As the 1 inch bore on the stones probably is not very accurate, Id probably even custom fit a bushing to each stone and epoxy it permanently in place.

    It seems to me that grinding stones are another product that is unusable as it comes new from the store. Sure, I can see retailers not wanting to stock 3 different stones with 3 different bores, but why can't we buy proper bushings and flanges? Maybe the market is all welders who don't care about balance.

    I am curious what people think of my observations.

    Regards,
    Boulter

  2. #2
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    Default Re: Thoughts on grinder vibration

    I'm a turner and use a 8" slow speed (1725 rpm) grinder. If you have the normal speed (3450 rpm) then you likely would have more of a problem.

    I generally agree with your observations but I think the stone is held in place with the washers and the plastic bushings only roughly centre the stone. After it is mounted and the outside diameter is trued then the plastic bushings are out of the picture. Now you can make an exaggerated drawing that says if the stone isn't perfectly centred then truing won't fix the problem but I think this concern is swamped by variations in the stone density which is probably where a lot of the problem lies. In other words, centreing and truing may not be capable of fixing the problem.

    The crappy washers can also contribute to the problem if they aren't a reasonable fit over the shaft.

    Various turners have reported very good results with the Oneway Balancing system from LV.
    http://www.leevalley.com/en/wood/pag...26&cat=1,43072

    This system compensates for stone density variations and is similar how mechanics used to statically balance car wheels in the old days.

    You should first run the grinder without wheels to make sure the armature is balanced.

    billh

  3. #3
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    Default Re: Thoughts on grinder vibration

    Quote Originally Posted by Boulter View Post
    Hi:

    I thought Id post this in the turning forum rather than power tools as it seems to me nobody needs a well behaved grinder more than a turner.

    What a PITA to get the vibration down on my 8 inch grinder. The grinder sounded like an aircraft, so I knew things were really bad in the balance department. I had a coarse OEM stone on the left side and the Norton white on the right. I wanted to move the white to the left side and mount my Norton blue on the right. I removed both stones and began playing with the white stone on the left side. I finally got lucky and obtained a reasonably low vibration. I do mean lucky, there was nothing deterministic in what I did that could be repeated to obtain the same result again. In fact, the Norton blue is not mounted because I couldn't get lucky twice.

    There is a tendency for severe and highly variable sideways wobble. I think most of the problem pertains to two issues. Firstly, the bushing plastic pieces that allows one to mount to a 1, 3/4 or 5/8 inches shaft have way to much slop. This arrangement must have at least 10 thou movement if not more. The second weak spot looks like the side washers (flanges?). I think they could be flattened and probably larger diameter too. In fact, at one point I mounted my 5 inch saw blade stiffeners (LV 16T01.02) and things looked much better, but they were rubbing against the shield a bit and I was worried about squeezing directly on the stones as opposed to the cardboard the OEM washers bear down upon.

    For those whom are unfamiliar with the LV saw blade stiffeners, see below.

    grinder 009.jpg

    When I get a metal lathe working again, I am going to machine a proper bushing for the centre hole, including reaming the 5/8 diameter, and maybe even making some big washers if I dont in the mean time buy a 3 inch set of stiffeners at LV for the purpose. Or maybe the bushings exist as a commercial product. As the 1 inch bore on the stones probably is not very accurate, Id probably even custom fit a bushing to each stone and epoxy it permanently in place.

    It seems to me that grinding stones are another product that is unusable as it comes new from the store. Sure, I can see retailers not wanting to stock 3 different stones with 3 different bores, but why can't we buy proper bushings and flanges? Maybe the market is all welders who don't care about balance.

    I am curious what people think of my observations.

    Regards,
    Boulter
    There have been a slew of posts about the problems with the cheap grinders we have, not just here but in other turner forums, especially the low cost lightweight chi-tiwan-nese high speed (3450 rpm) grinders. (high speed motors 3450 rpm use about half the copper windings, compared to regular speed 1725 rpm motors)

    The thought that the bushings are the culprit is I think misplaced mostly, these bushings have been around for decades, and they really place the stone in a approximate position on the arbor, the stone will have to be dressed to round after mounting, not just for this bit of off center wheel placement but to round the wheel itself, as the wheel it is basically poured like concrete and not always exactly round or even exactly balanced, (but that is another problem).

    In my opinion it is the stamped out flanges that are used, rather than machined flanges (that fit exactly square onto the arbor and against a good square shoulder where it keeps the wheel perpendicular to the arbor and prevents this side to side wobble), that is the biggest problem with these cheap grinders.

    You can still purchase a good Baldor grinder that just humms and not walks the shop, though you have to dig deep in your wallet for one of those.

    I think getting a low speed (regular speed) 1725 rpm grinder and trying it out in the store to start off with, so you don't get a real bad vibrating grinder would be a good start, then get the right kind of wheels for what you will use the grinder for, if you do have the vibrating problem a good investment IMO, is the Oneway balancer, it is a set for both wheels and replaces the cheap flanges with the machined flanges of the balancer set,

    http://www.oneway.ca/sharpening/index.htm

    that and a good wheel dresser and you can have a grinder that spins like a high cost Baldor.

    One other way is to find a used professional grinder, and you could be ahead of the game, I picked up a 240V DC grinder that I made a rectifier for and it sit on my bench justa humming away, so yes sometimes you can get the best for less, if you look around and get lucky

    Sorry Bill I'm a slow typer I guess, you must have posted while I was typing this, and yes I think we have similar thoughts on the problem
    Last edited by Leo Van Der Loo; 10-05-2010 at 03:52 PM.

    Have fun and take care
    Leo Van Der Loo

  4. #4
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    Default Re: Thoughts on grinder vibration

    Well, you did type more than I did, Leo.

    billh

  5. #5
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    Default Re: Thoughts on grinder vibration

    If the bushings do not always center the stone you will never get desired results. New bushings required.

    Note: the vibration could have a stone fly apart!

    Run the grinder with no wheels on it and then shut it off. It should sit still and just have a slight hum as it slows down. If the stones are on and everything is balanced it should sound the same.

    My sixty dollar grinder of no name seems to work well with no vibration.
    Egon
    from
    The South Shore, Nova Scotia

  6. #6
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    Default Re: Thoughts on grinder vibration

    Hi Guys:

    I don't have an issue with my grinder. It may be no Baldor, but with no wheels mounted, I just get a perfectly reasonable for my purposes low level "hum".

    Now that I have the one stone "tamed", I am not going to take it off except for a very good reason.

    I guess the Oneway system travels with the stone such that you can mount and unmount the stone without losing balance? I think one would want to be able to swap out stones and other accessories without having to rebalance. In any event, I don't think my shaft length meets the requirements of the Oneway system.

    Have a nice day ladys and gents.

    Boulter

  7. #7
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    Default Re: Thoughts on grinder vibration

    oy I've had a baldor for years, mostly it sits on the back of a shelf, but now and then I need to sharpen a lawn mower blade. I got it when I worked at an industrial supplier years back. It does just hum! guess I just took it for granted that grinders work

  8. #8
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    Default Re: Thoughts on grinder vibration

    I am more of a Spurt than an expert, but... It has been my experience that you are right about the slop issue. There is always some slop but too much creates bigger problems, especially when you change wheels. Each time a wheel is changed, it must be trued up. I use a diamond dresser, If it be 0.001 or 0.010 slop, the wheel will be slightly off center and need to be made round again. This will stop most vibs.
    Bill "Hickory" Simpson

  9. #9
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    Default Re: Thoughts on grinder vibration

    Quote Originally Posted by Egon View Post
    If the bushings do not always center the stone you will never get desired results. New bushings required.

    Note: the vibration could have a stone fly apart!

    Run the grinder with no wheels on it and then shut it off. It should sit still and just have a slight hum as it slows down. If the stones are on and everything is balanced it should sound the same.

    My sixty dollar grinder of no name seems to work well with no vibration.
    Bushings will never center a grinding wheel exactly, even the lead ones cast into the stone, would not do that, simple reason is that there has to be room to slide the grinding wheel onto the arbor, even at 2 or 3 thou that would create a 4 to 6 thou runout, enough to create vibration.

    The flanges will keep the wheel where it is set, and then you dress the wheel to round, you do this every time you change wheels.

    As for vibration making the wheel fly apart, I would say you would have a grinding dancing up and down before that would happen, oh and we did have a wheel fly apart one time, 14" or so size wheel 2 inches thick, new wheel with a flaw, it sure makes a mess of anything it hits, even 30 feet away, you better not be in the way or they will bury you, guaranteed , and that is no joke or off the cuff remark

    Have fun and take care
    Leo Van Der Loo

  10. #10
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    Default Re: Thoughts on grinder vibration

    Quote Originally Posted by Pat from Elora View Post
    Unless your grinding wheel is off balance alot or you have a bent shaft, you can cure the vibration and the 747 takeoff sound by putting a rubber pad or washers under the grinder. Bolt it down with the washer/pad in place. It doesn't move around enough to be a problem with accessories that are mounted to the table independantly (like a Veritas angled grinder attachment)

    Try it...you'll be amazed at the difference (even if your grinding stone is off balance)
    Good Point there Pat, To Dampen the Vibrations, Along with the other suggestions above
    Hey......Don't forget to make sure the Nuts are tight enough
    If the stone Is loose, enough to move through Its cycle, then you will have vibration..........Ok I'm gone to sweep the deck off.....We have some nice BBQ weather comming
    Dan From Rockwood ,Ont.

  11. #11
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    Default Re: Thoughts on grinder vibration

    A grinder with a balanced wheel doesn't need any rubber between it and the bench, or stand and it is guaranteed to work, rather than having the grinder vibrate on the rubber pad to take up some of the vibration.

    The tool you try to sharpen will vibrate with the grinder in that case as well, and that is exactly what you are trying to prevent.

    Have fun and take care
    Leo Van Der Loo

  12. #12
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    Default Re: Thoughts on grinder vibration

    [QUOTE][
    As for vibration making the wheel fly apart, I would say you would have a grinding dancing up and down before that would happen, oh and we did have a wheel fly apart one time, 14" or so size wheel 2 inches thick, new wheel with a flaw, it sure makes a mess of anything it hits, even 30 feet away, you better not be in the way or they will bury you, guaranteed , and that is no joke or off the cuff remark
    __________________/QUOTE]

    So a wheel has come apart!

    Whats to say it can't happen again?
    Egon
    from
    The South Shore, Nova Scotia

  13. #13
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    Default Re: Thoughts on grinder vibration

    Quote Originally Posted by Egon View Post
    So a wheel has come apart!

    Whats to say it can't happen again?
    I don't even think a grinder jumping all over the shop would damage a mounted wheel. Most damage to wheels is caused by shock due to dropping - they are brittle like a piece of glass. Another way a wheel may be damaged is an improper tool rest arrangement where a workpiece is thrust onto the wheel with excessive force and it is jammed into the rest. Grinding should always be a relatively light operation. If your TS blade isn't cutting well you know you need to sharpen the blade not push the stock harder into the dull blade. Same with grinders, if the wheel isn't cutting it needs to be dressed to expose sharp particles. This is particularly true of the gray wheels. Fortunately, most consumer grinders will stall if forces get too high.

    Before mounting any wheel I give it the "tuning fork" test. Put a dowel or drill bit through the hole and then lightly tap the outer edge of the wheel. After tapping the sound should have a short ring to it, not a dull clunk with no ring. The actual sound will vary with the size and material of the wheel. If it is a dull clunk then there is a good chance the wheel has a crack and it should be discarded.

    After mounting a wheel I stand to the side out of the line-of-fire when I switch the grinder on for the first time - not a good test the wheel is OK but a bit of caution.

    I handle wheels very carefully. Unused wheels are always kept in a drawer and ideally in a box. I never leave them where they might accidently fall on the floor.

    billh
    Last edited by billh; 10-07-2010 at 09:59 AM.

  14. #14
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    Default Re: Thoughts on grinder vibration

    Quote Originally Posted by Leo Van Der Loo View Post
    A grinder with a balanced wheel doesn't need any rubber between it and the bench, or stand and it is guaranteed to work, rather than having the grinder vibrate on the rubber pad to take up some of the vibration.

    The tool you try to sharpen will vibrate with the grinder in that case as well, and that is exactly what you are trying to prevent.
    I hear what your saying Leo....The stone must be true, Also the shaft on the grinder Itself should have no run out.
    I would think the rubber pad ,Say on a work bench would add to less noise and vibration that gets aplified through the work bench......I know some bench grinders come with rubber feet
    And If you tighten the grinder down too tight It will compress the rubber,And then have metal on wood
    Dan From Rockwood ,Ont.

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    Default Re: Thoughts on grinder vibration

    [QUOTE=Egon;310759]
    [
    As for vibration making the wheel fly apart, I would say you would have a grinding dancing up and down before that would happen, oh and we did have a wheel fly apart one time, 14" or so size wheel 2 inches thick, new wheel with a flaw, it sure makes a mess of anything it hits, even 30 feet away, you better not be in the way or they will bury you, guaranteed , and that is no joke or off the cuff remark
    __________________/QUOTE]

    So a wheel has come apart!

    Whats to say it can't happen again?
    The cause was NOT vibration, but an internal flaw in the wheel, never happens till it does

    Have fun and take care
    Leo Van Der Loo

  16. #16
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    Default Re: Thoughts on grinder vibration

    Quote Originally Posted by Daner View Post
    I hear what your saying Leo....The stone must be true, Also the shaft on the grinder Itself should have no run out.
    I would think the rubber pad ,Say on a work bench would add to less noise and vibration that gets aplified through the work bench......I know some bench grinders come with rubber feet
    And If you tighten the grinder down too tight It will compress the rubber,And then have metal on wood
    Dan my grinders have rubber feet, and are standing loose on the bench, the rubber helps to keep the grinder from sliding around, but if I had to do heavier work the grinder would be bolted down, the big pedestal grinders are bolted right down to the concrete, at least at our place and other places I have worked, and yes I agree the 60 pulses per minute of the electrical net will/can induce noise, and rubber feet would help eliminate or reduce that

    Have fun and take care
    Leo Van Der Loo

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