Facing my mill bed, considerations?
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  1. #1
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    Default Facing my mill bed, considerations?

    I'm thinking of facing the bed of my mill shaving off 0.1mm or so. The bed is quite old and worn, and prone to rusting, hard to clean properly and so on. The size is around 1500mm x 750mm.

    Is this a good idea, and what do I need to think of? Obviously this would be a "no fail allowed" job. What are these commonly made out of? Current table Z is -824.9mm. (Supposed to be -825mm.)

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    I would question how good your spindle is, as well as the ways (presuming this is a mill with dovetail or box ways). If either are suspected of being worn, just use the machine as-is until you can get it back to spec.

    If that's not an option throw a sheet of ~12mm aluminum on top of the table and mill it flat, dress as needed. Add tapped holes for mounting, you can do this before attaching it to the table. Just be sure you don't have significant temperature swings where the machine is located, as the table could warp from differential expansion. If this is an issue use a sheet of mild steel instead.

    The table is likely a cast iron alloy, but specific composition would be unknown without testing.

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    Milland,

    It's a Doosan Mynx 750/50 with 50 taper spindle 15kW power 305 Nm torque 40 tool capacity.

    img_20190909_112205.jpgimg_20190909_161215.jpgimg_20190909_161223.jpg

    The idea about a bed dressing is a good one tho.

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    Fadals mill their own tables


    Sent from my iPhone using Tapatalk Pro

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    Quote Originally Posted by ripperj View Post
    Fadals mill their own tables


    Sent from my iPhone using Tapatalk Pro
    Really? Must be prior to flaking.

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    Ever machined a long piece on only one side?
    Almost always the material will bend due to the change in surface stress from the cutting action....
    This will happen to your mill table...pretty much guaranteed.
    Unless you are planning on removing the table and scraping/grinding the ways true after surfacing the table face i would not do as you suggest....
    Better to go as "Milland" suggests...Make yourself a fixture plate to go on top of the existing table surface. Shim true and get back to cutting metal....

    Cheers Ross

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    Hm, yes. I do understand the consideration.

    Reason I was even asking in the first place is I've seen it done. My first trainee spot, they had a Mazak 4-axis where the pillar face was slightly off on two sides, and they did face mill it to correct the problem.

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    Don't do it, a sacrificial plate, as other guys have said, is the way to go.

    Regards Tyrone.

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    Quote Originally Posted by Tichy View Post
    img_20190909_161215.jpg
    I've seen much worse. Doesn't look nearly bad enough to warrant resurfacing, IMO.

    A fine stone and some very fine Scotch Brite on a quality random orbit sander (Festool ETS) should do a fine job at cleaning it up without affecting it dimensionally.

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    What does your indicator swept over the table surface tell you? Of course this is only after you know your mill is level and true. How long since you checked the level and that the Z-axis is perpendicular? Milling your table is rather hack IMO.

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    My largest machine, a 4" HBM came from a huge foundry. Makes you're table look pristine. Still a good machine otherwise though.

    My big vertical has a lot of table wear in a few areas. I just stoned everything down and it does fine.


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