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Thread: Precision Grinding a Hardened Shaft with an Improvised Toolpost Grinder

  1. #1
    Supporting Member Crusty's Avatar
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    Crusty's Tools

    Precision Grinding a Hardened Shaft with an Improvised Toolpost Grinder

    I needed to resize a piece of hardened shaft for a fixture I'm making so I made a mount for my angle grinder to use it as a toolpost grinder on my lathe. I started with a good sized chunk of 6061 and hogged out the middle to fit my grinder then drilled it to bolt onto the top of my lathe toolpost. I've got a ¾" roughing end mill that's worth its weight in gold and the mill area looked like an aluminum blizzard had just hit when I finished. The mount is nice and rigid when mounted.

    Since you can't reverse the grinder rotation the lathe needs to turn in the reverse direction so the surfaces meet in opposing directions. The lathe ways are shielded with some old jeans (wetted with water so they don't catch fire) and the grinding goes slow, never more than .020" off the diameter and feeding very slow, and you reach your target the same way you catch a unique rabbit - unique up on it ☺. The finished part doesn't have a $1000 ground finish because I used the wheel that came with my Hitachi grinder but it is dimensionally accurate and all it cost was the chunk of aluminum.

    In action

    Precision Grinding a Hardened Shaft with an Improvised Toolpost Grinder-grinder-mount.jpg

    From the backside

    Precision Grinding a Hardened Shaft with an Improvised Toolpost Grinder-grinder-mount-back.jpg
    If you can't make it precise make it adjustable.

  2. The Following 4 Users Say Thank You to Crusty For This Useful Post:

    baja (07-14-2020), celsoari (07-13-2020), Jon (07-14-2020), old_toolmaker (07-13-2020)

  3. #2
    Supporting Member celsoari's Avatar
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    celsoari's Tools
    Great work Crusty.
    Cheers
    Celso Ari

  4. #3
    Supporting Member Crusty's Avatar
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    Crusty's Tools
    The shaft turned out perfect and I've already used it to align a series of parts on axis.

    A fine better quality wheel would no doubt leave a prettier surface but dimensional accuracy was all that I required. Perhaps with a good quality wheel you might be able to hold to half a thousandth, though that depends on the accuracy of your lathe.

    Now that I've got a ½HP DC motor left over after my mill upgrade I think I'll use it to power an actual toolpost grinder with which I can do internal grinding with too.
    Last edited by Crusty; 07-13-2020 at 05:59 PM.
    If you can't make it precise make it adjustable.

  5. #4
    Supporting Member old_toolmaker's Avatar
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    old_toolmaker's Tools
    Crusty,
    A unique way to mount an angle grinder fo O.D. grinding.
    By the way .020” is a deep cut in one pass with the piece protruding that far out of the chuck.
    Dick


    Links to some of my plans:

    http://www.homemadetools.net/forum/f...6068#post65876 OFF-SET TAILSTOCK CENTER PLANS
    http://www.homemadetools.net/forum/s...995#post112113 SMALL TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/l...994#post112111 LARGE TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/m...383#post110340 MINI-LATHE CARRIAGE LOCK PLANS
    http://www.homemadetools.net/forum/s...191#post106483 SMALL QC TOOL POST PLANS
    http://www.homemadetools.net/forum/q...849#post119345 QUICK CHANGE LATHE TURRET
    http://www.homemadetools.net/forum/m...949#post119893 MINI LATHE COMPOUND PIVOT MODIFICATION

  6. #5
    Supporting Member Crusty's Avatar
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    Crusty's Tools
    It's between the chuck and the live center so a bit more stable and truth be told I never actually took more than a .010" cut off the diameter (.005" in on the dial).

    I've been looking for a better grinding wheel for my angle grinder hopefully with a finer grit and I haven't found one so far. Any suggestions where to look?
    If you can't make it precise make it adjustable.

  7. The Following User Says Thank You to Crusty For This Useful Post:

    old_toolmaker (07-14-2020)

  8. #6
    Supporting Member old_toolmaker's Avatar
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    old_toolmaker's Tools
    Crusty,
    I don’t own an angle grinder so I can’t comment on a grinding wheel recommendation. I believe the wheels normally used are resinoid bonded wheels which are resistant to breaking apart and usually don’t grind cool.
    Dick


    Links to some of my plans:

    http://www.homemadetools.net/forum/f...6068#post65876 OFF-SET TAILSTOCK CENTER PLANS
    http://www.homemadetools.net/forum/s...995#post112113 SMALL TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/l...994#post112111 LARGE TURRET TOOL POST PLANS
    http://www.homemadetools.net/forum/m...383#post110340 MINI-LATHE CARRIAGE LOCK PLANS
    http://www.homemadetools.net/forum/s...191#post106483 SMALL QC TOOL POST PLANS
    http://www.homemadetools.net/forum/q...849#post119345 QUICK CHANGE LATHE TURRET
    http://www.homemadetools.net/forum/m...949#post119893 MINI LATHE COMPOUND PIVOT MODIFICATION

  9. #7
    Supporting Member Crusty's Avatar
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    Crusty's Tools
    I found a few at MSC that would likely do a nice job (some CBN even) but they're really expensive. It's tough to find a hard wheel that can take the high rpms in my price range. I'll keep looking.

    The shaft did get hot so I had to let it cool several times before I hit my target diameter.
    Last edited by Crusty; 07-14-2020 at 10:30 AM.
    If you can't make it precise make it adjustable.

  10. #8
    Unkle Fuzzy's Avatar
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    McMaster-Carr has 60 and 80 grit wheels for 4 1/2" grinders for right about $6 USD ea.

    MSC is insane.

  11. #9
    Supporting Member baja's Avatar
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    baja's Tools
    Quote Originally Posted by Crusty View Post
    It's between the chuck and the live center so a bit more stable and truth be told I never actually took more than a .010" cut off the diameter (.005" in on the dial).

    I've been looking for a better grinding wheel for my angle grinder hopefully with a finer grit and I haven't found one so far. Any suggestions where to look?
    Try McMaster-Carr. They seem to have everything.

  12. #10
    Supporting Member Crusty's Avatar
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    Crusty's Tools
    Thanks all. I just ordered a couple of 80 grit wheels from McMaster and I'm waiting to find out if the shipping is double what the wheels cost. They look kinda flexible but we'll have to see when they get here.
    If you can't make it precise make it adjustable.

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