balancing the wheel
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  1. #1
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    Default balancing the wheel

    small surface grinder, 20x180 mm wheel. i static balanced 0.9 gramms out of it. i had some "fish scale" of not measurable depth. that is gone now, so i assume it was not the bearings. i still have a longitudinal pattern, though.

    how do i get rid of it? (Front edge is camfered by 30° or so.)

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    It may be more than balancing. wheel, material, machine, and method.

    Some times a weight added to the wheelhead can help on a small grinder grinding harder material, but you don't want to keep it there because it adds wear to the down feed works.

    Some small machines can have a better cross direction.

    QU: (Front edge is chamfered by 30°] the lead edge will chamfer itself as needed, Hand doing this can be detrimental.

    The forces of grinding can tend to pull/push the wheel head to take up and wheel head clearance to one side or to forward and back. temporary use of a food spring can alive this problem, again continued use will add wear to a machine.

    Some tines one-way long feed can help, to cross feed off the part and then travem only in the grind direction. for most grinders this is making grind sparke only traveling to the right.

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    you mean the head can tilt with cross feed? where would you put the spring? pulling to the side?

    btw, i thought it was interesting that balancing had a noticable effect. i have been hearing for years it would make no difference on such a small wheel.

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    A picture of the surface would help if you can get the light right.

    I'm a nut- Grinding Wheel Balancing

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    QT;[btw, i thought it was interesting that balancing had a noticeable effect.}
    Everything as an effect. Some shops only balance as needed. Some shops grin 95% of grinding with no balancing. Evey grind does not have to be a mirror finish.

    A close together shower of sparks can indicate 10 pounds of pressure on the wheel. That taken you can mount an indicator against the parked wheel head and then hand push every way to see if the wheel head takes a travel and stop in any direction. then think about how the grinding action might make the wheel travel that way.

    The spring would/might pull the wheel head to the direction the grinding action would pull it to a solid stop.

    A spring might pull the wheel head to the right of long travel and away or back for the cross at about 45%.
    The string watched all the time would cause mete wear to the up/down ways of the machine.

    The best cross feed direction might be indicated by a push-pull with an indicator to see if one direction is more solid, or just looking at grind finish to if one direction is better.

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    both surfaces are absolutely smooth to the touch: two grinds before balancing in front.

    after a few min. of grinding a slight scalloping reappears and goes away after a dress. what do you make of that? a slight imperfection in the bearings that gets impressed in the wheel?
    Attached Thumbnails Attached Thumbnails 0-098.jpg   0-096.jpg  

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    Perhaps that. Perhaps the wheel is loading and getting dull so beginning to bounce and needing the early dress. Perhaps the column clearance, Perhaps the long trave feed rate, the amount of stock removal.
    I would start with the low-cost trials and work up to rebuilding the spindle and motor bearings.
    If the wheel is the problem I might buy a name brand white AO wheel two letters softer so it might break down, and do balance it. If column clearance I would check that out and might try adding weight and a spring. looking good and going poor might suggest the long travel way method is OK.

    Agree you can have a wheel that is too soft..I normally start with a K hardness and then go softer or harder as needed. That only works with the same brand wheel because every manufacturer has its own idea of what each hardness might be.

    I would not argue against balancing. if you put on a wheel and use it up you might balance every wheel. If the work requires often changing the wheel on the same mount you might balance as needed. adding a mount-up mark on the mount and on every wheel can help to save the balance and the dress when changing wheels.

    if money is no object you can start with rebuilding the spindle and motor.

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    That second image looks like the wheel has picked up something or has some grains that haven't broken down. The pattern is close together, assuming normal travel rates. Balancing problems usually make a pattern that's a bit coarser. You can figure it out by knowing the wheel RPM, feed rates and pattern pitch.

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    Whoa! How much crossfeed are you doing per pass? That looks like a LOT!. Try about .100in or so to start. Also what is your depth of cut that you feel you should chamfer the wheel edges?

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    conrad, the machine has been grinding like that for years until i balanced the wheel. it looks much worse then it is, the pattern shows with very thin blueing, though. cross feed is 1.5 mm and i finish with 0.01 mm doc and a spark out pass (usually 3 mm cross). actually one edge has been camfered by accident but is handy sometimes.

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    Quote Originally Posted by Conrad Hoffman View Post
    Conrad, have you ever read about/thought about making one of those automatic balancing devices, that consists of a circular track containing a number of bearing balls and some oil? The idea is that if the system is unbalanced, the balls tend to move to the side that is lighter. Here is a video that illustrates the idea

    Centramatic Automatic Wheel Balancers Demonstration - YouTube


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