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Thread: Table Extension Question

  1. #1
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    Table Extension Question



    Alright, you were helpful with the joint between the legs and rails of the table idea I'm working on so let's see how you do on the next puzzle. I'm trying to work out an elegant, yet not over-engineered solution. (I'm trying to turn over a new leaf on that over engineering thing. ) In this view you can see that the top has been split and the leaf is about to be installed. The leaf is 22" wide so I figure the top halves each need to slide out about a foot to allow clearance. After the leaf is installed the top can be pushed back in.

    So, how do I attach the top to the leg assembly to allow the halves to slide? It needs to be strong enough to allow the table to be picked up by its top because someone will do it.

    I did a search for table extension mechanisms but everything I found was too bulky. Any ideas? Thanks.
    Irony: The opposite of Wrinkly

  2. #2
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    dave i am not an engineer and may be looking at this to simply but why couldnt you incorparate a large dovetail in your top frame and leg mechanisum that would allow the main sections to be pulled out and back in yet have some strength like the old slides had. the top insert could be connected threw pins and holes like the old tables did.. just a redneck engineering problly wont work but it might trigger your mind to somthing that will i hope .
    If in Doubt, Build it Stout!
    One hand washes the other!
    Don't put off today till tomorrow!

  3. #3
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    My first thoughts were along the lines of Larry's suggestion. Then I coughed up an overengineered hairball idea. I'm not even sure if this is doable, but could you take short ball bearing drawer slides and mortise them into the top frame? If this could even work, you'd have to mount the portion on the table so that when the table halves are closed, the slides are "pulled out". Those would only be about 1/2" thick if they could be made to work.
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  4. #4
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    Dave,
    Larry right the dovetails will work.
    "There’s a lot of work being done today that doesn’t have any soul in it. The technique may be the utmost perfection, yet it is lifeless. It doesn’t have a soul. I hope my furniture has a soul to it." - Sam Maloof
    The Pessimist complains about the wind; The Optimist expects it to change;The Realist adjusts the sails.~ William Arthur Ward

  5. #5
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    Alright, sliding dovetails. I thought about your suggestion, Doug, and haven't completely dismissed it yet. I might come back to it. In the meantime, I thought I'd see about sliding DTs. I am worried about have the tail made of wood because it could expand and contract with moisture changes and this would change how the top slides and fits. So I came up with the bright idea (well, maybe not so bright. Ok, dim idea) of using Delrin or UHMW for the mating parts of the sliding DTs. The pieces mounted to the top would be in stopped dados that would run a little longer than the plastic parts. The holes nearest the center would be round but all the rest would be short slots so the table top can exapand and contract as it will.

    The tails are split into chunks so that the leafe doesn't have to have dados across the full width right at a point where the leaf would be stressed if someone leaned on the edge of the leaf. There would be some mortises cut instead for clearance over the short pieces of DT.

    when the table is closed up without the leaf installed, none of the works are visible. Except for the split down the middle, there's be no sign that the table is an extension table.

    I'm also thinking that some small stops could be worked out to to prevent the top pieces from sliding out completely but could be released to remove the top if desired.

    I found another little detail in a drawing of this table that may make me rethink this arrangment but so far it doesn't seem too bad.
    Irony: The opposite of Wrinkly

  6. #6
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    Slow to respond on this, but how about the 3 part wood mechanisms like used on a lot of tables. They are 3 pieces and you would attach the center piece to the frame, the rest are free.

  7. #7
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    Travis, I looked at those but they are too bullky.
    Irony: The opposite of Wrinkly

  8. #8
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    Hey Dave,

    I started thinking about this, and then realised the el-cheapo table I have in the kitchen slides open, yet the legs don't move. Here's how they did it:

    Attachment 4030 Attachment 4031

    It's a simple version of what I think Larry suggested. You could change the openings/rails to dovetails, instead of the ones shown, but these are easier to make.

    If the 'holes' in the apron don't bother you, than this idea is probably one of the easiest. It would mean adding a center apron though, for the slides attached to the underside of the top to slide into to.

    While you're designing your table, have you given any thought to making the extension a gullwing, with the leaf "hidden" inside the table until it's needed. I decided, the first time I saw a table that did that, that any dining room table I build will incorporate that feature...

    See how I am...make the slide easy, but complicate the leaf...

    - Marty -
    Fivebraids, Inc.
    When you earnestly believe you can compensate for a lack of skill by doubling your efforts, there’s no end to what you can’t do…

  9. #9
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    You're right, they are too bulky. I like Marty's table the best I think, dovetails on the top not on the frame.

    I especially like the "hiding" leaf. That would be way neat!

  10. #10
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    Dave,
    You don’t pick easy ones, do you?

    I don’t have much of a feel for woodworking, but it is difficult for me to imagine that dovetails could sustain the moment at the ends of the stringers were the table picked up with leaves extended.

    Any mechanism that would come out through the ends of the stringers seems to affect the clean lines of the table.

    What I would do is this: (Assuming 6 ˝” overlap of extended leaves & stringers.)
    • Get some heavy extruded and anodized aluminum T-track.
    • Mill a groove in two stringers to accept the track, stopping the groove about ˝” short of each end. The groove would be slightly deeper than the height of the track.
    • Remove by milling, the top legs of the track three inches each side of its center.
    • Drill and countersink for screws along the length of the track.
    • At the center of the track(s), drill a ˝” dia. hole.
    • At the center of the stringers, drill and tap ˝-13 x ~ 2” deep.
    • Using a fixture that keeps the top of the track flush with the top of the stringers, bed the track in epoxy. Cure.
    • Screw the track down.
    • Mill Delrin tee sections (4), about 5 5/8” inches long that are sized to fit the track sections in hand. Attach them to the inner ends of the sliding leaves.

    Now, the sliding leaves can be dropped into the track, pulled out, and a ˝-13 SHCS can be screwed into the center(s) of the track for a stop.

    To further strengthen the tabletop, how about this?
    • Make a 2 tube/1 rod sliding assembly that incorporates springpins and detents to keep the rod engaged to both tubes when extended.
    • Take each of the edge pieces that run under the table parallel to the slide direction, and split in half with a bandsaw.
    • Mill hemispherical grooves through them, again stopping short of the visible ends.
    • Embed the ˝” I.D. steel tubes into the grooves and glue each piece back together.
    • After assembling the first leaf to the table, insert the two ˝” dia. steel rods into the tubes, and push them all the way in.
    • Assemble the second leaf to the table, pull the rods back from the first leaf, and engage the second. Now the rod will float between the two leaves.
    • Construct the parts beneath the center leaf as a downwards facing C section, so the rod supports the leaf ends.
    • If desired, a detent or lock could be used here as well.

    I look forward to seeing both how the original is constructed and how real woodworkers approach this challenge.

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