Permanent magnetic chuck or electromagnetic
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  1. #1
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    Default Permanent magnetic chuck or electromagnetic

    I've done a little bit of grinding on a walker permanent magnetic chuck and actually that wasn't so bad. I have the option to upgrade to an electromagnetic chuck, walker magnet controller paired to a Magnalock-corp chuck and wondering if I should do that or not.

    I imagine it's better to go with the electromagnet if you have the chanc. Both chucks look to be in pretty good shape overall. I have no idea which of the two has more holding power.

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    More holding power isn't always what you want. If your workpiece has a bow in it, more holding power will just suck it down. To work the bow out, you want to block it in and use the least amount of holding power you can get away with. That's the main advantage of the electromagnet; you can adjust the power.

    Dennis

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    Electromagnetic chucks are electrical parts heaters.Chuck gets warm,machine gets warm part gets warm, time is wasted waiting for it to demag.Good luck trying to hold a tenth.Leave your set up over night come in the next morning,oh look,power failure,your set up is laying on the cement floor with a trashed out Neubold fixture. Electo chucks are good for large wet grinders used for grinding large plates or blocks that you can not pull off by hand.If I need less holding power on a permanent mag chuck I just block up the handle.Consider the cost of the elecomaag controller and what it costs to replace or repair.I like a Walker fine pole,front to back lams. Be sure to grind the bottom of a new chuck first, not flat from the factory.Hold downs on right side of chuck tight,hold downs on left side snug to allow for linear expansion along the chucks length.

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    Before wire EDM I spent man years in front of the surface grinder grinding die sections for progressive dies. So flatness was always important. Using an electromagnet chuck is the way I would go. You have control over the magnetic force, better allowing you to improve the quality of the work when it really counts.

    Roger

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    While an electro magnet does indeed produce heat, any serious grinding will use coolant. Anytime the chuck is on the coolant should be on.

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  9. #6
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    My experience is the strength of magnetic chucks vary:
    Wide pole permanent chuck--Lowest
    Narrow pole permanent chuck
    Wide pole electro mag chuck
    Narrow pole electro mag chuck--Highest strength

    This is my opinion based on experience--Yours may very

    Holding power is dependent on part thickness, length and width. Wide pole is good for thick stuff, Narrow pole for thin stuff, but not exclusively. A good grinder hand can always find a work around.

    The best combo for me is a narrow pole electromagnetic chuck with a neutrofier (mag strength control).

    Electro mag chucks do warm up. If you are grinding all day--better have coolant. Small jobs on a manual machine probably do not need coolant .Can always get by with a spray bottle of sol oil.

    Lost

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    Got a 10 x 24 Hanchett Magna-lock on a DoALL 1030 and a 6 x 18 B & S fine pole permanent on a B & S 618. Both are fine chucks. I tend to like the permanent better, it does not change temperature. The DoALL has flood, the B & S mist. That said, never had an adjustable power supply for the Hanchett - it came with the old (Make than ancient)DoALL controller re-worked by a PO to be a simple rectifier box. (on/off) It was possible to grind (carefully!) with residual, though.

    If you can afford the controller, a good electro chuck is very convenient. It will most likely have greater maximum power as well.
    It does take a long time to equilibrate, but for most of us that might not matter. The permanents tend to be less expensive and there are no electronics to go bad. But eventually the lever will get sticky and bindy.
    smt

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    I am using a narrow poles Walker electromagnetic chuck on my Jones & Shipman. Works well but neither the permanent magnet nor the electromagnetic are perfect. The variable power on the electromagnetic is nice, but not always combine the holding power and prevents deformation, especially with thin pieces. I usually cement those to a parallel and then grind one side to make it flat.
    Heat can be a problem too. For precision work I attach the work-piece and run the table with coolant flow for about an hour before grinding. This allows the chuck, the work-piece and machine to stabilize.

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    Much a matter of personal like/dislike. For me, I liked the electromagnetic for greater holding, variable control on thinner pieces, and the de-mag. The only thing I didn't like was grinding while a storm was brewing outside. More than once power was momentarily interrupted, shop lights blinked, and that caused the workpiece to skate on the chuck (timing is everything) while my heart skipped a beat. There's also the heat factor and coolant isn't always possible with some jobs I've had. I have a permanent on the grinder and simply block in better, that's part of pre-grind check anyway regardless of the type of chuck. There are advantages to both so it's your preference.

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    Quote Originally Posted by AD Design View Post
    Much a matter of personal like/dislike. For me, I liked the electromagnetic for greater holding, variable control on thinner pieces, and the de-mag. The only thing I didn't like was grinding while a storm was brewing outside. More than once power was momentarily interrupted, shop lights blinked, and that caused the workpiece to skate on the chuck (timing is everything) while my heart skipped a beat. There's also the heat factor and coolant isn't always possible with some jobs I've had. I have a permanent on the grinder and simply block in better, that's part of pre-grind check anyway regardless of the type of chuck. There are advantages to both so it's your preference.
    I agree and would add. I have used both also and would ask how much work will you be doing on the grinder? What size is the machine? What kind of machine? Made for accuracy or just clean up grinder, etc.

    Most 12" x 18 or bigger machines Do-all, G&L, Maddison, Thompson, Okomoto, etc. are beefy and were designed to use a heavier mag chuck. Smaller machines for the most part use perm. chucks. I would also consider the extra weight and a need for extra way oil or pump oil more often. If I had to grind or have a part ground I would scrape one side so it was flat so i didn'thave to worry about them bending or a bend pulled down. the guys mention blocking, this is also a great way to avoid twisting but you need to set the part on 3 points of non magnetic blocks and block around the part with magnetic blocks to trap the part. Also I would put a Precision Kurt vise in the chuck to hold the parts if I could that helped so the parts would not warp.

    Also it is so important to use flood coolant, cold blaster, spray air mister or a hand squirt bottle to cool the parts. Another idea is to buy an portable or table top 110 v de-magnetizer to be sure the magnetic charge is gone. Most of the expensive electro chucks have a de-mag, but I have found many don't work so good. I know i could write more, but I'm sure others can add more. Rich

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    My surface grinder came with a "permanent electromagnetic chuck". The chuck is magnetised by a controlled electrical current passing through a coil. But after the current stops, the chuck remains magnetised. When you want to remove the part, the controller demagnetises the chuck and the part, and you lift the part off.

    This has advantages: you can control the magnetic strength, if the power fails, your part stays on the chuck, and there is no continuous heating.

    Main disadvantage is that it costs more, and the controller is more complicated than the controller for a regular electromagnetic chuck.

    I have one of these on my surface grinder, because that's what it came with. I like it a lot, but I don't have experience with any of the alternatives.



    Cheers,
    Bruce

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