Holding a plate with a big pocket?
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  1. #1
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    Default Holding a plate with a big pocket?

    I am trying to figure out the best way to approach holding a plate with a giant pocket. The part is 316, 16" by 8" by 0.650", starting with 0.100" over size plate stock. There are four M8 tapped through holes in the corners. One-off part.

    My original plan was to use Talon Grips across two vises. Op 1 does all the features, then I flip it over and face off the Talon Grip carrier thickness. I am worried that the part will warp under vise pressure as the large center pocket gets opened up.

    I came up with two other ideas:
    1. I could face the back and do the outside profile first, then flip it over, bury it in the vise jaws, and do all the front-side features, hit the big pocket last.
    2. Or I could face the back, then put in the threaded holes. When I flip it over, use M8 bolts to hold it from underneath on an aluminum carrier plate. I am not sure 4xM8 is enough to hold up against the roughing forces though.


    Any wisdom? Am I overthinking it?

    access-plate.jpg
    Last edited by trochoidalpath; 04-05-2021 at 01:09 PM. Reason: fix stupid typo

  2. #2
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    Firstly Minor glitch / typo - how are you going to get 0.650 thick part from 0.100 stock?

    As for machining, I'd go for option 2, .........cos if 4 x M8 bolts don't hold that, then you are doing something very wrong

    Just my 2 cents, as ever YMMV

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    First thing I'd do is face mill it, then blast that big pocket open leaving stock, unclamp the vises and let it banana.
    Reclamp the vises and finish the faces & holes.
    Flip it, tie it down and finish the part. You'll have to do some clamp hopping though.

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  6. #4
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    Quote Originally Posted by Limy Sami View Post
    Firstly Minor glitch / typo - how are you8 going to get 0.650 thick part from 0.100 stock?

    As for machining, I'd go for option 2, .........cos if 4 x M8 bolts don't hold that, then you are doing something very wrong

    Jusat my 2 cents, as ever YMMV
    LOL, I meant 0.100" oversize.... thanks!

  7. #5
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    Using talon grips, clamp the crap out of it, release and reclamp lighter. Eliminates bowing, the indents in stock will keep it from moving. Plus what dew said, rough with plenty of stock, release and reclamp

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    My 2 cents, have your local waterjet shop drop the slug out first. That saves you from doing the heavy stock removal and need for heavy fixturing.


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