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How to build a long table top?

5923 Views 4 Replies 5 Participants Last post by  Waldschrat
I am interesting in building a dinning table e.g. 70 inch long. How to build a long table top, since most of lumbers are either cup or slightly bend? Any trick?

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Just a few ramblings here for you to consider. Plywood with a vernier of your choice I got out of that "Everything needs to be solid wood syndrome" a number of years ago. You will get a better finished product and much more stable. As far cupping or warping if you insist on the solid wood way to go just make sure you check the moisture content and let the wood acclimate to the environment of your shop for at least 4 - 6 weeks and keep it at around 8 - 10% moisture content, I even let it sit for a few days to a week if I have to take a lot off on the planer. Oh and finish the bottom as well and put a few leafs in to keep the working parts smaller?
Hey Angi
after takeing sanhills suggestions then get straight material or get thicker material and joint and plane it flat, . let your material normalize in your shop for as long as possible before milling it. It's recomended to alternate the groth rings up and down when glueing your top together also make sure your edges have been jointed flat . even better use quarter sawn wood to help minimise wood movement. A common mistake is to connect your your top in solid manner instead of connecting it so it can move with figure 8s or grooves and wooden clips.
sandhill and Jim have offered some good suggestions. I would probably use thicker stock, glue it up, then find a pro shop with a widebelt sander to take it down to final thickness. I have no clue if that is an option for you. It depends on where you live. A planer will follow the curve of the material length-wise, as well as flatten the cup as it planes. You still need to start with straight boards as much as possible, but in sanding after the glue-up, the pieces keep each other straighter. Jim's last suggestion is also a very good one. The structure of the table will help the keep everything straight and flat too.
-Yup, let it acclimate to your shop, which hopefully is dry enough to get your wood to around 8 to 10% or so.

Here would be my tip if you decide the solid wood method, its easy and relatively quick…. not to mention the perferred method over here for doing solid wood glue ups and keeping tables straight for tables for centuries. Works great and never fails! just see if I can describe it correctly ;-)

-rough cut (rip) the individual boards to about half an inch bigger what what yoiu need in width

-joint two sides, then plane the other two sides lightly to see what you got for lumber (imperfections and what not, I am not certian of the quality and condition of lumber you are starting with

-lay out the wood and try to arrange the boards so that they are "heart on heart wood and sapwood to sap wood" this is the first step to controlling warping! mark them with numbers on the end so you wont plane away the order.

-plane out the lumber to about 1 mm over the thickness what you need… then rest you can easily take off from sanding (half a mm from either side ) after the glue up…. Glue up the boards in the order that you wanted, using hardwood packers and a flat surface to help keep the glue up straight.

-after glue up you can use a sliding dovetail from perpendicular wood. 1 sliding dovetail every 40 cm or so will work for a table of 70 inches 3 ought to do the trick. you can cut the dovetail with a router and a guide rail quite easily.

-cut the dovetail piece and slide it in the slot where it belongs gluing the back side so it does not stick out when the table shrinks in winter with less moisture. If you want to get really fancy, you could do this all but leave one board out of the table surface out and glue it on after you slide in the sliding dovetail wood piece and you would seen nothing from the outside, not to mention you have a great advantage of being able to attach the the table to the sliding dovetail with out having to worry about movement, because it slides on the dovetail how ever it needs and it stays straight.
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