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  1. #1
    Join Date
    Aug 2012
    Location
    Australia
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    645

    Default Safe rotational limits of 4E cast iron?

    I have a 150mm disc ~24mm wide that I am intending to use on my bench grinder as a lap. The cast iron is 4E grade. Before switching the 2800rpm machine on I thought it best to see if anyone knows the safe rotational limit? I did some reading on car flywheels which are much larger and rotate much faster but they are likely a different grade of cast.

    Any thoughts on the safe rotational limits of 4E?

  2. #2
    Join Date
    Jun 2008
    Location
    Victoria, Australia
    Age
    74
    Posts
    5,080

    Default

    I wouldn't worry about it, the tensile strength of 4e cast is likely to be better than that of grinding wheels. In any event, I imagine the guards for grinding wheels would be still there.

    I've been using diamond lapping disks, and they work a treat on carbide. http://www.cutandslice.com.au/specials

    I also got some from a cheaper Chinese source, but I've lost the URL, BobL might remember where the supplier, he was the one who found them.

    Found it, http://www.thk.hk/online-cart.php?cid=36&sid=39 600 is good for shaping, 1200 and 3000 are good for polishing or touchup.

    Ray

  3. #3
    Join Date
    Jul 2011
    Location
    Melbourne Australia
    Posts
    1,376

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    Ray.

    Where did those magnetic backed laps come from? And have you tried them yet?

    Also, how good an edge does that #3000 give you. I imagine its slow, but is it better?

    Regards Phil.

  4. #4
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    6,216

    Default

    Engine flywheels are often cast iron, and they do many many rpms...

    Quote Originally Posted by RayG View Post
    Found it, http://www.thk.hk/online-cart.php?cid=36&sid=39 600 is good for shaping, 1200 and 3000 are good for polishing or touchup.

    Ray
    They are a bit cheaper here http://richontools.com/index.php?mai...ndex&cPath=1_9
    Gold, the colour of choice for the discerning person.

  5. #5
    Join Date
    Jun 2008
    Location
    Victoria, Australia
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    74
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    5,080

    Default

    Quote Originally Posted by Machtool View Post
    Ray.

    Where did those magnetic backed laps come from? And have you tried them yet?

    Also, how good an edge does that #3000 give you. I imagine its slow, but is it better?

    Regards Phil.
    They came from the "cut and slice" mob, I have mostly been using the others without the magnetic backing, they hold just fine with the nut and washer against the backing disk.

    No idea how the 3000 compares with the cast iron diamond lapping plate, maybe we can do a few experiments one of these days when I'm down that way.

    Ray

    PS Just for comparison, I think the 3000 grit works out to about 4-8 micron grit size, so you'd think it would be comparable to 5 micron paste.

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