Dining table tops

[Brad McCollum]

Hey everyone, I've been asked to make some dining tables and am fairly new to this type of woodworking. These tables will vary in length from 4-8 feet long and 36" wide. My biggest concern is wood movement over time. this first group will be rustic pine, others will be oak, maple ect. what is the best way to join the boards to prevent splitting and joint failure? This may turn into a new income stream for me. Thanks for all your help.

[Prashun Patel]

You might google around 'understanding wood movement'. There is a bunch of good free info on the web about this.

At the risk of oversimplifying all that, here are a couple rules of thumb i use:

- Wood moves in its width, so be careful not to constrain movement in that direction. That means if you put breadboard ends on, you have to attach them in slots in a way that allows the long boards to move a little.

- Attach the apron in a way that allows movement in the top's width also. Figure 8 fasteners & pocket screws are just 2 ways of doing this.

- If the wood will be stained or the grain is fairly uniform or uninteresting, then warping can be minimized by using narrower boards, say in the 4-6" width range.

- Many people say to alternate the arch of the growth rings on adjacent boards. But I'm in the camp that says dry yr wood properly and arrange them for the best visual appearance.

- Topcoat both the top and bottom sides of the tabletop. The topcoat alters the way moisture is absorbed into the wood. You want this effect to be the same on both the top and bottom.

- Make sure the boards are dry. If yr doing a bunch of these, investing in a moisture meter might be a good idea. Also, when you surface the boards, try to take approximately equal amounts off the top and the bottom. Plane/joint/rip yr boards close to final dimensions, and then let it acclimate for a few days before final milling.

[G Douglas Fowler]

There are many techniques and mechanical fasteners available to secure the top to the apron and allow wood movement. Two sources are Graves, Dining Tables and Charleswoth's Furniture-Making Techniques, Volume Two. While you are doing your research you might also check into how to select your boards to minimize distortions.

[Sam Murdoch]

Good for you Brad to score this batch of work! As for your concerns and questions - the reason table tops ultimately fail - crack- is because they are attached improperly to the base. Your next post should be asking how to attach a wooden table top to its base :).

The glue up of the plank top is pretty straight forward and we all have our systems. I start by buying lumber that is thicker than I need. For a 7/8" thick plank I use 5/4 lumber. For an 1-1/16" I would buy 6/4 etc. I spec., dressed two faces & ripped 1 edge and ask for the boards to be from short lengths. If I want 6' boards I don't want the lumber supplier to dress 2 faces of a 12' board then cut it in half. You typically end up with curved and likely unusual planks. Better to dress 7' or 8' boards. Sounds counterintuitive but there is a lot less waste that way. I always buy at least one more board per section than I need. If I am building 2 or 3 panels I will get at least 2 or 3 extra boards. You can't expect that all your stock will be just what you need. If you have the time or inclination to pick your own stock these considerations are easier to accommodate.

In the shop I begin by making absolutely certain that each board in the group is flat and straight. My jointer 1st, then thickness planer for the faces and the table saw and jointer for the edges. I then lay out a top on my work table selecting the best arrangement of boards for color and grain. Then I joint the edges to fit their mates. Here you could just glue and clamp, but I will use either biscuits or Festool dominos in order to get my tops as aligned as possible. The biscuit is good for this but the domino is KING.

Biscuits or dominos are not intended to add strength or better connection for the table top (the modern glues are very effective without help) but are really used to maintain nicely aligned boards. This step is immensely helpful for clamping during the glue up and make clean up of glue ooze a cinch. That's it. OH - and if you absolutely must hide the end grain you will need to use "bread board ends" - no miter trim or other type of locking frame. Have fun.

Sam

... and while I was writing my book here, others have added their thoughts on the matter. Some good advice above, as expected. :D

[michael case]

Brad,
Sam is right. Job one is going to be truing and squaring you stock. You need to get good at this. Personally, I would always pick my stock, but even if you hand pick your still going to have to start with stock that is wider, thicker and longer than your intended finish and mill it to size yourself if you want the kind of accuracy necessary for professional results. Then your going to want good clamps. Your going to find a hundred opinions on clamps. I use the Bessey Revos but, others will swear by their old pipe clamps or insist that you must use steel bar clamps. This is a road you have to travel in your own way. Sam is also right in that you do not need any reinforcing biscuit etc. except maybe for help with alignment. Sometimes it easier to make several narrower panels that will fit in your planer. True them after joining and then glue them to each other to make your big panel. Also guard against letting your glue skim. If you try to make one big panel and don't watch it your glue will skim while your working and your panel will pop apart in short order. You might find it very helpful go to the library or the book store and do some reading on milling lumber and basic woodworking.

[Brad McCollum]

Hey Y'all,
Thanks a bunch for the advise. I've been doing some research online and most of the work seems pretty straight forward, nothing I haven't done before, just a different application. It seems the biggest concerns are board selection, dryness and glue up practices and sealing the bottom as well as the top. Here is a pic of the first one. This one is all pine. Made some mistakes but good practice.
230744

[Kent A Bathurst]

Brad....looks good.

You have all the right info on making the tops. I've never had any trouble with mine - from, say, 16" x 24" up to 44" x 84". All QSWO, IIRC.

Three things I would add to your thought process:

1] I almost always attach my tops with the classic "Z-clip" style of table top fasteners, in expansion slots. Available everywhere, but I get mine from McFeely's - 25/box, inexpensive. But - there are a bunch of methods for attaching.

2] After you have glued up the top, never, never, NEVER store it laying directly on a flat surface. You can sticker it to allow air movement, or [my version] just stand it up on its edge somewehre out of the way until you are ready to sand, or finish, or attach it. Keep it stickered or standing up between stages in the process. You will be resoundingly surprised and disappointed to see the warp in that top after only a day of laying on a flat surface, since it is getting unequal airflow. This applies to perfectly dried lumber. Do not ask how I know this, nor why I have some shelves in the shop that were ripped down from nice QSWO glued-up panels.

3] In the same train of thought on #2....here's how I prep my boards for glue-up:
> Rip over-width. On my dried QSWO, this is usually 1/4" - 3/8" oversize.
> Joint one surface, and joint and square one edge. I don't necessarily completely joint the surface...I do enough to have a good surface for the planer, which may mean some patches that are not cleaned up.
> Plane the other surface. Again, I only plane it so that I have cleaned up most of the surface, but there are often some patches that are still rough. Ideally, take off about the same amount of fiber as you did with the jointer, if possible.
> Then either sticker these boards, or [my version] stand them on edge. Leave them alone for 2 days.
> This approach removes fiber and allows the board to release any internal stresses.
> Then, when you are ready to glue it up, go back through the process, removing fiber in roughly equal amounts from both sides. Rip to final width, joint edges as/if needed. Glue and clamp "right away". By which I mean, just move through the steps in sequence to glue-up, versus final machining and wait till later in the day or the next day. The critters won't really move once they are glued up in a larger assembly.

[ian maybury]

Just a related question on adhesives for this sort of application, and hopefully not a hijack. Until recently I would simply reach for Titebond (actually a local equivalent PVA), but I've been reading that it can't be re-glued. i.e. applied over itself in a failed joint to make a repair. Also that PVAs unlike true structural adhesives like polyurethane and epoxy may creep under prolonged stress.

It now seems that they are sensitive to loss of strength if permitted to skin, which means no taking chances with the already pretty short open time.

I used liquid polyurethane on a recent project, and quite liked it (easy to spread, easy to trim, good bond if gaps are tight) except that it seems to produce a darkish glue line. Epoxy and plastic resin/urea formaldehyde may be other options.

Does anybody routinely use any of these other adhesives in this sort of work where appearance matters? Especially where more open time is needed.

What's been the experience?

ian