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Thread: Automatic slab flattening jig?

  1. #1
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    Automatic slab flattening jig?

    Brainstorming here, could use some ideas from the more creative elements here.

    First, yes I know I should just buy a big CNC router, but that isn't going to be a justifiable expense for this. I have a stack of slabs that need flattened and used for countertops and tabletops for a project. I'm bookmatching them and ending up with up to 50" wide and about 80" long. I klodged together some scrap steel that was laying around and got a wide span conventional jig working, but...., this is just the most torturous thing I've ever undertaken for the sake of woodworking. The slabs are normal live edge ash stock, some places 1/2" has to come off, some places is only 1/32" or so. Problem is, by hour 4, I had made it halfway through the first side of the first one.

    Having plenty of time to ponder my bad decisions, I got to thinking about mechanically automating the process. Maybe even Diy something CNC, but there has got to be a way that I can get that router auto fed across this slab so I can do something else while it works. There are very few new problems or solutions, so some other easily bored person probably already has a solution. Ideas???

    First thought was to use a big reversing thread lead screw to move a router carriage, but I don't have one, especially that long. Auto progression could be done with a cam and pawl, something like on a saw filer. Probably a better idea out there though.

  2. #2
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    Buy an old metal working planer or big shaper. Should be able get one in decent shape for scrap price plus rigging costs.
    Bill D.
    https://www.youtube.com/watch?v=TTI4dewA1QE
    Last edited by Bruce Page; 03-13-2022 at 7:25 PM. Reason: Removed eBay link per TOS

  3. #3
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    [QUOTE=Bill Dufour;3183097]Buy an old metal working planer or big shaper. Should be able get one in decent shape for scrap price plus rigging costs.
    Bill D.
    https://www.youtube.com/watch?v=TTI4dewA1QE


    Interesting Bill, I didn't know those existed. Seems a bit ambitious on price, but the concept is sure sound. I have the same big drill press as in the first pic, so this would fit right in. Wondering how a shaper would do it, oh I see your youtube link, I'll have a look.
    Last edited by Bruce Page; 03-13-2022 at 7:26 PM.

  4. #4
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  5. #5
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    That's a nice machine, same idea I had, a whole lot more refined. Wonder what they are using for a head... I could build the steel stuff.

  6. #6
    There is a reason why we get a 10x premium for slabs. There just is no cheap way to do the work. It's either a big expensive machine or an even more expensive person.

  7. #7
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    Quote Originally Posted by johnny means View Post
    There is a reason why we get a 10x premium for slabs. There just is no cheap way to do the work. It's either a big expensive machine or an even more expensive person.
    100% agree. We don't do enough slabs to justify spending big $ for a machine. This project is for an upgrade to our own offices, one of those weekend type of deals. Flattening these dang things are not how I want to spend the day off, so basically I'm just finding excuses to build a machine rather than shove a router around for hours.

  8. #8
    Is there a cnc shop within striking distance? Sub it out.

    You could take out the major twists and humps with a power plane and winding sticks and run them through a large planer. Maybe cut several channels with your router sled first and connect the dots. Or do one side roughly with the router and then thickness plane.

    I have flattened slabs with a router sled a couple of times and it is, indeed, tedious. 4 hours to do only half of a 25" x 80" plank seems excessive though - you should be able to hog off 1/8"-3/16" x 1" wide at a whack with a 15 amp router.

  9. #9
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    To bad I'm not close to you Steve. I looked at the CAMaster map and the closest machine of size in your area is at Rapid City so still far away. It can handle 12' lengths in one setup. I'm good for 8'.

  10. #10
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    Matt Cremona is working on a very large slab flattening table that uses a large motor to drive a large piece of tooling. It looks like a CNC, but is not computer controlled. Feed can be all manual or motorized on the Y (long) axis with lateral adjustments manually (and indexed) for each pass. While what he's building (from a kit) is not inexpensive, it's a whole, whole bunch less money than a CNC of anything close to the size. Matt will be keeping that unit at his warehouse because of the size. I suspect he'll have a full video of the build at some point, but he has been sharing short reels on Socials for awhile now.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  11. #11
    Just kind of thinking in the wind here, may be worth something or may not. You'd need to make a frame to lay the wood on along with something to track the cutter down. For the cutter pick up on of the newer Craftsman RAS with the cast iron column along with the rotary cutter that replaces the blade. Rig the mechanism to raise the head and attach the thing to the carriage. It would work similar to the router one where the cutter moves, and that cutterhead will cut about 4" each time.
    To see what they look like, do a google search on "craftsman rotary planer attachment".
    I've used one on a RAS, they will flatten wood but it leaves it very rough due to the rotary cutters.

  12. #12
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    Buy a used panel saw. Mount a router in place of the saw. or use apowered plane in place of the router. I think they have about 2-3" wide cutters.
    Bill D

  13. #13
    How wide is each slab? Take them to a mill and pay them to flatten them for you. Undertaking a single slab flattening is painful. ďA stack ofĒ them I canít imagine doing with a sled.

  14. #14
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    Slab size is 50" wide by 84"ish long. They are live edge so that's the max dimensions. I hadn't thought about finding someone "local" with a CNC to do it. None in this town, but I send a truck to Rapid weekly, so that might be a solution. I looked at Camaster and don't see the map, will look again.

    I guess it could be something we do more frequently if I had a good way to flatten, customers love slabs. Going to look into the panel saw idea too, I know where one of those are collecting dust. Definitely want to use a bigger motor and cutter. I'm using a big spiral flute in my biggest router right now, 4 hours for half of one of these slabs is the pace I can get. I could definitely use a router upgrade, it would help but I don't think it'd be a dramatic improvement. Will look into the RAS motor idea.

    Off to google Matt Cremona, thanks for that lead too!
    Last edited by Steve Rozmiarek; 03-13-2022 at 1:13 PM.

  15. #15
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    Got any young folks near you that might like to earn some extra money? Pay a decent wage, make sure your rig is safe, and turn 'em loose. Cheaper than building something you might not use again.

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