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IndustryArena Forum > MetalWorking Machines > CNC "do-it-yourself" > Catahoula's router/mill build - welded steel with EG
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  1. #1

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    Mar 2020
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    42

    Catahoula's router/mill build - welded steel with EG

    The beginnings of my fixed gantry router/mill. 40 hours of fabrication in the books since last Friday. Most tubes and hollows to be filled with epoxy granite after stress relief and machining. Still need to do the columns, but pretty close to done with the welding. Proud of my baby 110V welder for surviving with this super heavy wall steel-- greatly aided by a 300-400 degree F preheat, though. Low power makes it hard to weld over the tacks and keep it looking nice, but overall I think good for minimizing heat, and penetration is enough for this stiffness-critical machine. I started out doing a lot of stitch welding to minimize heat, but after working on the frame and feeling vibrations move through the structure, I decided to fully weld everything except the long, heavy rail mount bars, but using more narrow stringer beads than weaves where possible. Preheating thick steel plus proper weld sequence makes this take about 10x longer than it would otherwise!

    Tip: granite countertop scraps are readily available at the used building materials stores. $5, and flatter than about anything short of a blanchard ground top or actual surface plate.

    Thanks for all the help so far; great forum.
    Attached Thumbnails Attached Thumbnails PXL_20201103_042344747.jpg   PXL_20201106_024550586.jpg   PXL_20201106_035808606.jpg  

  2. #2

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    Mar 2020
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    42

    Re: Catahoula's router/mill build - welded steel with EG

    Question for the forum- I will have the long steel flats milled to accept linear rails at a local machine shop. The machine in question is an absolutely massive old Hydrotel milling machine, so fitting this on the table is no problem. Apparently the machine is quite accurate, but I don't have a way to verify this. Should I have shoulders machined for both rails of each pair? Or just have one side of each pair done with a shoulder and let the other rail be adjusted to match? Obviously I'd prefer to have the rails a completely set-and-forget affair with two shoulders, but if the two shoulders aren't very close to parallel it won't be much good. Thoughts?

    Edit to add: I've also worked with the machinist to figure out a workholding situation in advance, so I'm pretty confident that my router frame will fit up on the machine table without much distortion or flex.

  3. #3
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    Jul 2012
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    Re: Catahoula's router/mill build - welded steel with EG

    You should first stress-relieve the whole thing if you seek accuracy.
    If you think you can enhance the flatness of the mounting surfaces after the milling (by scraping, grinding, lapping, ...), you should not mill shoulders for the rails as they will be annoying to work around.
    Note that these shoulders in small hobby mills have absolutely no benefits regarding lateral forces. They are only useful for installing the rails quickly IF they are milled accurately to about 0.01mm/m. If the mill can't achieve that, you can do a whole lot better by aligning the rails manually with a precision straight edge.

  4. #4
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    Jan 2008
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    Re: Catahoula's router/mill build - welded steel with EG

    An alternative to shoulders is to get the side of the rail mounting milled so you can indicate along it.

    This means a shoulder is not in the way if you need to scrape the mounting surface.
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  5. #5

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    Mar 2020
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    42

    Re: Catahoula's router/mill build - welded steel with EG

    Thanks guys.

    jackjr- definitely going to have this commercially stress relieved in a large vacuum oven. Walls are heavy so am optimistic about the resulting stability of the structure. Agreed about lateral forces- shoulders would just be to provide a hard datum edge. I did find a 36" straight edge at Shars tool for $450 USD, which is less expensive than I'd thought (starrett is $1k usd), Thanks for the guideline on straightness, that's very helpful. I will check with the machinist to see if 5 tenths over the whole thing is a reasonable ask.

    pippin- interesting idea. But maybe if the machine is good enough to mill a datum edge it will also be able to mill accurate shoulder? I may have the edge milled as well for good measure though.

  6. #6
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    Re: Catahoula's router/mill build - welded steel with EG

    Datum edge doesn't lock you in.

    You can double check with a straight edge / master reference.

    Hard to adjust a shoulder.

    Also errors in different planes may not be the same.

    Known good machine - shoulder should be fine.
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

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