Does anybody part off in an HMC?
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  1. #1
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    Default Does anybody part off in an HMC?

    I have a job that I'm quoting that doesn't look like there's a good way to hold it except for holding a long (about 18") bar on a pallet in a horizontal, and milling it (couple different angles) and then parting it off on the machine.

    Part is about 1.25 long. There's a weird shaped hole that has clearance for a 5/8 keycutter in the middle of the part. And I was wondering if anyone has parted off parts in a horizontal before?

    Specifically, the idea I am having is using a keycutter around the outside first, then finish parting off from the inside, and I am hoping for the keycutter to catch the part. Operator would then unload the part from the keycutter.

    Anyone ever done this? It doesn't seem too dumb to me. Not a ton different than catching parts with a boring bar on a lathe.

    Material is a bronze alloy.

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    I have never seen a reason to part off entirely in a horizontal. It eliminates the ability to pallet change, which is half the incentive.

    Why not leave it hanging by a tiny tab or onion skin you can easily break off?

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    I've done this in a vertical with a keyseat cutter but I did leave a tab (as mentioned above) and twisted off the parts.

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    Just leave a tab. You're gonna have to debur it anyway, tab or cutoff completely. Cutting off completely without something else supporting the part isn't going to leave a stellar finish.

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    The only reason was because a tight dimension from an angle on top to the bottom of the part where I'm parting off is +/- .001 and was hoping to avoid having to run it over sandpaper.

    But now that you've mentioned that and I've written it out, I'd have to sand it anyway where it finishes cutting off. Duh

    I guess the tab idea works for me.

    Now the part is somewhat circular, fits within a 1" diameter. Where would it be best to leave tabs/skin? I still think it would be better to cut from both the inside and outside with the keycutter. Should I leave a .010 wall all the way around? Or something different? I have not left skin/tabs for breakoff before.

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    When I part off a tube-like part on a VMC I use a slitting saw around the OD, leaving about .005" or less holding by the ID. This makes it easy to clean up by flat sanding and/or deburring tool.

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    If you circular cut from the outside, leaving a thin (.005/.008") inner "tube" to retain the part on the stock, perhaps after break off you can use a countersink to remove the thin ring and not have to touch the ends at all.

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    Maybe sumpthing like this on the OD and ID in stead of a flat woodruff cutter?

    item detail


    ---------------

    Think Snow Eh!
    Ox


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