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  1. #1
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    Default Surface grinding wheels

    I'm going to try some surface grinding in my mill. It seems like a cup wheel is what I need. I have a magnetic "chuck."

    What do I need to know about choosing wheels? My current need is to grind imperfections out of 3" x 3" 4140 square plates, sightly hardened (Rc ~40). I need toem to have a mirror finish when I finish the grinding/polishing process.

    Thanx, guys.

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    Forget it unless you just want to say it is a ground finish and have a worn out mill. The difference between a grinding machine and a cutting machine is not the tool. The entire machine is built to much greater rigidity and precision. Grinding with your mill will not be the slightest bit better than a milled surface, it will just look different.

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    In addition to what was said already, grinding does not generally produce a mirror finish. You need lapping for that. Grinding on a mill is asking for trouble. Grinders are specifically designed to prevent as much grit as possible from getting into places you don't want it for machine longevity. I would steer well clear of grinding on a mill.

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    Quote Originally Posted by abstruse View Post
    I'm going to try some surface grinding in my mill. It seems like a cup wheel is what I need. I have a magnetic "chuck."

    What do I need to know about choosing wheels? My current need is to grind imperfections out of 3" x 3" 4140 square plates, sightly hardened (Rc ~40). I need toem to have a mirror finish when I finish the grinding/polishing process.

    Thanx, guys.
    What T just said.

    EVERYTHING about a mill is a poor fit to grinding.

    Planer can do it. Even an angle-grinder on the end of a shaper ram HAS done it.

    But even so it ain't quite right.

    Watcha doo is send stuff like that out. To folks who HAVE a lot more than just the one grinder, a whole lot more than just the one wheel, and a serious investment in chucks, dressers, dirt collection, through-wheel coolants, and a ton of fixtures for mounting the goods.

    Did I forget to mention "experience"?

    Because it s their Day Job. For more than just the one "day".

    And only the competent AT it get to survive for ANOTHER day.

    You can hire a small increment of that goodness under THEIR roof waaay cheaper than you can acquire even the tiniest part of it under yer own roof. Investment ain't the half of that. Learning curve is the killer of time.

    Which isn't ordinarily all that costly, anyway.

    Cheap enuf, more than one or two of us even start-off with stock bought that way. Already all-over Blanchard ground. Work it with care. De-burr. Pack and ship. Done. Go earn a crust on the NEXT job instead of f*****g around.

    "Mirror finish"? If you plan to BUFF them? Sounds as if all yah really need for starting point is lumped under "Blanchard ground", whether the machine doin' it was made by Blanchard or never.

    A true "Mirror" finish? A grinder is only the pre-prep anyway. Lapping makes mirror-grade surfaces. Tedious process. Very!

    And even then? Ignorant SOFT steel ain't worth the bother of it.
    Last edited by thermite; 10-24-2020 at 06:11 AM.

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  6. #5
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    "Did I forget to mention "experience"?"

    Yes you did, you certainly do not have any..."experience". What was that mt2 said?
    Get some photos out there for some street cred! Get with it termite!

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    Quote Originally Posted by donie View Post
    "Did I forget to mention "experience"?"

    Yes you did, you certainly do not have any..."experience". What was that mt2 said?
    Get some photos out there for some street cred! Get with it termite!
    Bite my OTHER ass, yah infantile pretentious pre-pubescent pinworm-porker!

    I shed earwax as has forgotten more about metalworking of a Manhattan lunch "hour" than you'll live long enough to ever learn.

    Not all that hard, given you've been so dam' busy makin' yerself out a "COVID orphan" you ain't yet begun the learnin' process...

    Such a fine son yer poor Mum has had to put up with!
    Last edited by thermite; 10-24-2020 at 09:12 AM.

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    termite, there are rumors, your Hong Kong banking years, was really your Hong Kong jewelry store clerk job you lost before the .88 cent an hour stock boy job?
    It just doesn't add up brain boy!

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    Quote Originally Posted by donie View Post
    termite, there are rumors, your Hong Kong banking years, was really your Hong Kong jewelry store clerk job you lost before the .88 cent an hour stock boy job?
    It just doesn't add up brain boy!
    And nor do you. Just leave it out for goodness sake, you are boring.

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    With trashing your mill you will need buy a mill and a grinder.
    The mill with ways riding over grits will lose any/most chance of a good finish.
    Fly cutting HSS or carbide bit with about .03 horizontal flat will give a good mill finish(not mirror).
    Mirror finish is tough even on a grinder.

    Often an 8 or better micro finish will take a 320 to 500 grit wheel, needs a very good spindle, some ball and roller grinders can't do mirror finish, not likely a mill can run smooth enough to not burn the finish even wet.

    Lap or hone to mirror is most common.

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    Fly cutting HSS or carbide bit with about .03 horizontal flat will give a good mill finish(not mirror).
    Although not 4140, I have used this method many times on 6061 T6 aluminum. Use oil on the cut, then lap with alcohol on a surface plate with 1000 then 2000 grit wet dry sandpaper. Keep it clean.

    Then finish off with a bit of polish on the paper side of the sandpaper.

    It's good enough for a hermaticity tester, that uses Helium for a seal test.


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