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Dusting Magnetic Chuck Question

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  • JoeLee
    replied
    Originally posted by dian View Post
    so did you grind the chuck in the meantime? i wonder if you relieved the brass strips.
    No, not yet. I just got the wheel a couple days ago.
    Now I have to get myself in the mood to spend the better part of the day doing it.
    There are no brass strips on my chuck, leaded segments.

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

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  • dian
    replied
    so did you grind the chuck in the meantime? i wonder if you relieved the brass strips.

    Leave a comment:


  • JoeLee
    replied
    Originally posted by metalmagpie View Post
    What model is your K.O. Lee grinder? I am buying one and will probably have questions and I'd love to have someone to correspond with if you're willing.

    And when I got my first SG I got a decent Walker chuck from the honest to God real Al Babin and had to grind it in. The K.O. Lee instructions said to grind the bottom of the chuck just to cleanup first, then to do the top. And they said you HAVE to use coolant. I rigged up a 5 gallon bucket with a garden pond pump. Finally, when you are done, put 5 identical blocks on the mag chuck. I per corner and 1 in the middle. Then grind all 5 with the same wheel height. Debur with a smooth hard stone (the edges) and measure them with a tenths mic. Lots of mechanical problems will manifest in this simple test.

    metalmagpie
    Mine is an S718 HG. It came with the B&S chuck. the chuck surface had some nasty nicks in it but worked fine.

    When I was restoring the machine I brought the chuck to a local machine shop to have them grind and clean it up after I milled about .020 of the surface. They did it on a slightly larger grinder that had coolant. He did both top and bottom sides. I think he flipped it twice.
    I never touched the table. It still had the fancy factory lace pattern that KO put on a lot of their older machines. Not sure what they call that. It's not a scraping or flaking. More like something you would get by rubbing an abrasive rubber eraser on the iron. Strictly decorative I believe.
    I dusted it in after I mounted it, but that was about 20 years ago. I'm going to do it again. I went with a 7 point test because there were some discrepancies I found around the center of the chuck.
    If you have any questions about these machines you can PM me.

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

    Leave a comment:


  • metalmagpie
    replied
    What model is your K.O. Lee grinder? I am buying one and will probably have questions and I'd love to have someone to correspond with if you're willing.

    And when I got my first SG I got a decent Walker chuck from the honest to God real Al Babin and had to grind it in. The K.O. Lee instructions said to grind the bottom of the chuck just to cleanup first, then to do the top. And they said you HAVE to use coolant. I rigged up a 5 gallon bucket with a garden pond pump. Finally, when you are done, put 5 identical blocks on the mag chuck. I per corner and 1 in the middle. Then grind all 5 with the same wheel height. Debur with a smooth hard stone (the edges) and measure them with a tenths mic. Lots of mechanical problems will manifest in this simple test.

    metalmagpie
    Last edited by metalmagpie; 04-24-2020, 02:04 PM.

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  • JoeLee
    replied
    Originally posted by JRouche View Post

    Bummer. You can remove the same amount with the wide wheel. Cut the depth of cut down. Less heat. Oh well. Cut some grooves JR
    Well, I already got the 46 grit J wheel in 1/2" width. It'll do the job, just takes about double the passes. At least I'm on the side of caution.

    JL................
    Last edited by JoeLee; 04-24-2020, 11:13 AM.

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  • JRouche
    replied
    Originally posted by JoeLee View Post
    Mikey, thanks for the explanation. Now I understand what your saying. I am going to go with the original 1/2" wide wheel, not going to try the 1" for all the reasons stated in the other posts.
    Dressing the chuck isn't the time to experiment with wheel widths.

    Since a lot of mfg.s wheels are offered with a recessed center I have to assume that it's purpose is to adapt to machines that are designed for 1/2" wide wheels.

    JL.......................
    Bummer. You can remove the same amount with the wide wheel. Cut the depth of cut down. Less heat. Oh well. Cut some grooves JR

    Leave a comment:


  • eKretz
    replied
    Actually now that I have thought about it, there was a difference - the motor was lower RPM for the larger wheel. 3600 vs. 1800 as I recall. HP was not different - 2 HP in both cases. So I wouldn't change the wheel diameter radically without capability to control wheel speed. But changing to a little wider wheel may or may not be fine - it will depend on the individual spindle.
    Last edited by eKretz; 04-18-2020, 08:27 PM.

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  • JoeLee
    replied
    Originally posted by eKretz View Post
    Critical speed can probably be more appropriately described as any speed at which the wheel/spindle combination vibrates in an uncontrolled manner - or at a "resonant frequency." This can occur at multiple different places in RPM range, not always necessarily faster.

    As far as wheel width, many grinder spindles are designed to be used with different sized wheels. Although the main wheel used with most smaller grinders is 7" OD and 1/2" wide, larger wheels can definitely be used with some. My own B&S 818 Micromaster came with a 7" wheel by default, but was available from the factory with the OEM 2HP direct drive spindle with up to a 12" diameter and 1" wide wheel. The only difference was the wheel and the wheel adapter, same exact spindle.
    This is where all the conflicting views become confusing.
    Especially going from a 7" wheel to a 12" on the same spindle only difference being the motor HP.

    I've used 1/8", 1/4" and 1/2" wide wheels on my grinder with no issues and also 3 1/2" cup wheels for special jobs.

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

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  • eKretz
    replied
    Critical speed can probably be more appropriately described as any speed at which the wheel/spindle combination vibrates in an uncontrolled manner - or at a "resonant frequency." This can occur at multiple different places in RPM range, not always necessarily faster.

    As far as wheel width, many grinder spindles are designed to be used with different sized wheels. Although the main wheel used with most smaller grinders is 7" OD and 1/2" wide, larger wheels can definitely be used with some. My own B&S 818 Micromaster came with a 7" wheel by default, but was available from the factory with the OEM 2HP direct drive spindle with up to a 12" diameter and 1" wide wheel. The only difference was the wheel and the wheel adapter, same exact spindle.
    Last edited by eKretz; 04-18-2020, 01:37 PM.

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  • JoeLee
    replied
    Mikey, thanks for the explanation. Now I understand what your saying. I am going to go with the original 1/2" wide wheel, not going to try the 1" for all the reasons stated in the other posts.
    Dressing the chuck isn't the time to experiment with wheel widths.

    Since a lot of mfg.s wheels are offered with a recessed center I have to assume that it's purpose is to adapt to machines that are designed for 1/2" wide wheels.

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

    Leave a comment:


  • mikey553
    replied
    Originally posted by JoeLee View Post
    Not sure what you mean by "critical speed"
    The wheel would be the same dia, just double the width. There is a weight difference but if balanced I don't know how the spindle would see it.

    The more I think about this I think I'm just going to take a shot with the 1/2" 46 grit J wheel.

    JL..............
    Every rotating shaft (in your case the grinder spindle) experience vibration during operation. The frequency of this vibration is the same as running speed (in simple cases).
    In addition all shafts have their own natural vibration frequencies, so called critical speeds. Critical speed is the speed, at which the amplitude of vibration grows very significantly.

    If your running speed is close to the critical speed, you will experience a serious amount of vibration even if you balance your wheel very good. If your grinder spindle is running at 3600 RPM, its design first critical speed is most likely much higher than that, let's say 5500 RPM. So with regular 1/2" wide wheel you don't have big issues with vibration. But when you install 1" wide wheel, you are changing the spindle dynamics, which depends on the rigidity of the shaft and bearings and the weight (and its distribution along the spindle) of various spindle components. The wheel is a part of the rotating spindle. Heavier wheel means the first critical speed drops down from 5500 RPM and may come close to the running speed of 3600 RPM. In such case you will experience high vibration and accelerated bearing wear.

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  • sarge41
    replied
    Originally posted by JoeLee View Post
    Understood, but that would be defeating the purpose of the 1" wide wheel. I can see where it would work in a pinch.

    JL................
    My point was that if you have a wide wheel, and are having a chatter problem, this is one way to ease the problem and not spend several days getting it done. My experience comes from working in a job shop, not a hobby shop where you can use all the time you need. Good luck.

    Sarge41

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  • JoeLee
    replied
    Originally posted by sarge41 View Post
    JoeLee: Another trick I have used when using a wheel that is wider than usual, is to dress part of the face off. that is to say the wheel face was originally 1.00" wide, but I would dress away 1/4" perhaps .030 " dp to reduce the width of the active face. Wide wheels can chatter pretty easy. Good luck.

    Sarge41
    Understood, but that would be defeating the purpose of the 1" wide wheel. I can see where it would work in a pinch.

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

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  • JoeLee
    replied
    Originally posted by mikey553 View Post
    When you run wide, heavy wheel on the grinder not designed for it, you are changing the dynamics of the spindle. Heavy wheel means your critical speed is reduced comparing to a normal wheel. Who knows - you may end up running on the critical speed and, trust me, you don't want to do that.
    Not sure what you mean by "critical speed"
    The wheel would be the same dia, just double the width. There is a weight difference but if balanced I don't know how the spindle would see it.

    The more I think about this I think I'm just going to take a shot with the 1/2" 46 grit J wheel.

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

    Leave a comment:


  • JoeLee
    replied
    Originally posted by Tim The Grim View Post
    From October of ‘74 to March of ‘04 I worked in 19 different shops, 23 different times. Not once did I ever use a 1” wheel on a manual grinder.
    Auto feeders with coolant yes, but not on a handle pumper. Just sayin’. 😷
    Yes, that is why I asked for some input. I'm very leery of running the 1" wide wheel.
    It was recommended by the CGW tech. I figured that's why they have the recess, so they can be mounted on a machine that takes a 1/2" wide wheel.


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

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