Table Top Question

[Norm]

My son would like me to make a coffee table like the one shown here.



I've got some slabs of black walnut that I'm going to use so it will be 8/4's thick and one solid piece. Can you folks give me an idea of how you'd do the joinery on this.

Thought I'd add the dimensions are 66"x24"x16"

[LeeB]

Mortice the sides between the top and bottom. Don't make one long mortice though. Three short ones about 4" wide x 1 1/2" long x 1 1/4" thick. Be sure and run all the grain in the same direction so it doesn't tear itself apart when it shrinks and swells. If you have a biscuit joiner you could also use it. Double biscuits every 4". M&T will be much stronger though. LeeB

[Ianab]

Mortise and tennon would work, although I would offset the tenons toward the inside so the mortices were further from the end of the top and bottom slabs. Otherwise biscuits or dowels would be fine as well.  I would probably go with dowels for simplicity. They are after all just small round floating tenons  ;)

Make sure the grain in the upright pieces is vertical to prevent having a crossgrain joint.

Should look good in solid walnut   

Cheers

Ian

[metalspinner]

MT is a great idea.  I would use a "floating tenon."  Rout slots in each piece to align with each other, then insert a tenon with glue and you're good to go.

[Furby]

The top and bottom are between the two sides in the pic.
Would it be better to have the sides between the top and bottom?

[LeeB]

sides between top and bottom would look better IMO. You could also miter everything and use a grooved miter spline or biscuits. For the spline, route a stopped spline and use a plywood spline. All boards would have to be flat and true for it to look good, but that would also hold true of the other way. LeeB

[isawlogs]

 Maybe it would look better , maybe not ... it dont matter, diss is what he wants .  ;)  I would use Double biscuits , orient all da wood in the same direction .

[Don_Papenburg]

Yep , I like the sides between top and bottom also .  That way dowels, loose tennon, or bisquik joints would work.

[WDH]

If you want to get fancy, a sliding dovetail would be a very nice visual feature showing the joint as part of the piece.  Since the piece is fairly simple, the sliding dovetail could liven it up a little and show your skill as a woodworker  8).

[LeeB]

The sliding dovetail would also be a very strong joint and hold up ot the abuse a coffee table takes without ever worrying about the joint failing. LeeB

[Norm]

Thanks for all the tips folks. I had planed on putting the sides between the top and bottom for this one. It just seemed like it would be more stable that way. I hadn't considered using a sliding dovetail and just may give it a try, I've never done one before. The mitered edges is a neat idea too but not sure how to do it with such a big piece.

I was kind of worried that it being one big slab about the movement but of any wood I work with walnut would be my pick. It's kind of funny, my son showed me the picture and asked if I could make him one. Sure lets go see what we have already dried...and not on the bottom of the stack. Now I knew he wanted it to look like the picture so when he saw those big walnut slabs I had the first thing out of my mouth is we can use them but no way will I paint them. Here's some soft maple if you want painted furniture. Bless his heart he decided that natural walnut would look better than painted maple. I'll make a woodworker out of him yet. :D

[brdmkr]

Norm,

With using stock that big, and putting the sides between the top and bottom, I wouldn't hesitate to use glue and biscuits.  Not that I am lazy  ;), but buscuits and glue would be EASY if you have a biscuit joiner.

That sliding dovetail would be cool too.  Do you have a big enough router ;) ;)

[Furby]

What about moving that hunk of wood?
Most folks are just gonna grab the top and lift.
Wouldn't want it falling apart. ;)

[Norm]

I'm making him sign a liabilty release Furby. :D

[WDH]

Norm,

If you put the sides between the top and bottom, you could cut the male part of the dovetail on the side pieces without too much trouble on a router table because the side pieces would be the shortest and not too hard to handle on the router table.  You could clamp on an extentsion fence on the router table to give the fence more height so it would be easier to keep the side pieces flat and plumb while you run them thru.  You could also take several passes and sneak-up on the final dovetail dimension rather than trying to plow off all the wood in one pass.   For the top and bottom, the two largest pieces, it would be easy to rout out the dovetail slot using a clamped on guide.  You could make the first pass with a straight bit that is no wider than the narrowest dimension of the dovetail slot if your router cannot handle the dovetail slot in one pass.  That dovetail joint will be the strongest way to join the pieces if you orient the top/bottom and the side grain so that they expand and contract in the same dimensions.  That way, you could glue the entire joint, and it would be super strong.  The exposed joint will really add a nice visual feature to the piece.

It would be easiest to use glue and buscuits, but there is something about the elegance of the sliding dovetail that might make the little bit of extra work worth it.  Plus, you will not be glueing long grain to side grain (a much weaker joint) with the dovetail.  If you go with the dovetail, size the width of the dovetail and dovetail slot to be in a pleasing proportion to the thickness of the wood you are using, not just whatever width the bit is. 

Walnut is a great choice.  Some in-process pics would be nice!

[Norm]

Thank you for the tips WDH. I like the looks of sliding dovetails but am a bit intimidated by them. Since it's such a big piece with some unique slabs in it I'm going to biscuit the sides and top together. I have visions of getting it all prepped and screwing up the dovetails. He's not going to see the humor in a shorter table after I have to cut it down to fix it.  :D

If this weather will warm up I'm going to take the slabs over to the wm and rip them into rough sizes. I'll take some shots of the progress.

[metalspinner]

I don't think bisquits are going to give you the strength you want to keep that piece together. 8/4 walnut slabs are heavy.  Not to mention the abuse a coffee table will take over the years - like picking it up from the top. This is a good opportunity to use your new router for much stronger joints. ;)  Any of the MT joints or dovetail joints mentioned are not difficult and will let you sleep better at night knowing they will stay together forever.

[Norm]

Yeah your right metalspinner, I was talking to Patty about it and decided I'd practice on some scrap pieces to learn how and then use them on this piece. Never going to learn if I don't try.

[Gary_C]

Norm  How are you going to make the bottom? If you have just one big flat bottom, it may not sit flat on the floor. You could raise up the lower cross slab and have it set on the sides, or just glue four small blocks on the four corners.

[Patty]

That is a good idea Gary...raising the bottom piece up an inch or so off the floor and letting the piece sit on the two side pieces. Gonna have to think about that one for a while.  smiley_sidelightbulb

[metalspinner]

Never going to learn if I don't try.

8) 8) 8) 8)

That's the FF spirit!

[Gary_C]

Two other things, actually just one, that you should consider while you are thinking.
Scale and proportion. Judging from that picture, I would guess the top, sides, and bottom are all at least three inches thick. If you are using two inch thick slabs that will probably plane down to maybe 1.75 inches, that table will look different than the picture. Are you going to be happy with that different look? One way to help decide is to draw it out to scale and then decide. I suspect the table in the picture is hollow construction to get that appearance without using massive slabs that will require that low boy to move. You could make it appear thicker by adding strips of wood to the front faces.

Sorry I didn't see this sooner. If you have already started cutting, forget what I just said. 

[Part_Timer]

What about drilling throught the top and into the legs with LARGE dowels made out of a contrasting wood.  Maybe 1" dowels.  Then if you pick up the bottom an inch or so between the sides you could drill through the sides and into the bottom.  Just a thought.

[TexasTimbers]

A sliding dovetail is not hard Norm. It only seems intimidating until you start laying it out. But the setup has to be properly laid out. Just make sure you have good support when you the ends across your router table. Run an end piece across your table with your bit lowered like an Olympic skiers dry run - a couple of times to make sure you have a feel for a piece that heavy. You want know you can keep them plumb and against the fence without it wobbling as you run it across. Any wobble at all is not tolerable.

Your top and bottom are a different story. You can't run those across your table. You are going to have to run the router across the top and bottom slabs IMO. You could do it across the table but, the waste is going to pile up behind the joint, and it will add heat to the process you don't want .... if it stays built up around the bit - and it will unless it is removed because it has no way to get out then it will burn the wood and prolly bog it down.  It would be better to have someone follow behind you a couple inches away with the shop vac pulling the waste from the joint as you move the router along against a WELL-secured straight edge. I emphasize well-secured because you want to be able to keep plenty of pressure against the fence with the router so it doesn't want to wander off even a little. If the male and female portions of the joint are not perfectly straight, putting the joint together could destroy the joint, and once you have it halfway in, and discover it isn't going to go all the way - good luck getting it apart without doing more damage.

I suggest doing some test pieces. If you find that the female part of the joint is contankerous, one of my own shop tricks is to just cut a groove with a spiral bit first, slightly undersized from what the norrowest part of the dovetail bit will cut at the top of its profile, then finish oit off with the dovetail bit. The wood AND waste removal, avoiding excessive heat build-up, and ability to run straight are all dramatically enhanced by adding this extra step.

Not rtrying to make this more difficult than it actually is, but these are some challenges you may encounter.

Always dry-fit your joints completely. If they will not slide together relatively easy but without any slop, the joint is not right. This is why uyou cut test pices so it is not too tight, not too loose! ;)

[Larry]

The question for me on your design is how do you treat the end grain to make it attractive?  Been thinking for couple of days and finally sketched couple of designs to see what I could come up with.  Did a google image search to see iffen I could come up with something similar.  First thing outa the box...

http://www.ericmanigian.com/port/calvin_01.shtml

Click on "home" for the top view.

Variable spaced dovetails as a design element.  Tails on the top but the pins are a little to thick, and resemble router cut to much for me.  Guessing, but I bet he cut em on a bandsaw and cleaned them up by hand.  A little wood flour goes a long ways to cover up mistakes.

[TexasTimbers]

Now that you bring up design, and we are departing KISS,  here's another possibility. This isn't a very good pictutre but if you use your imagination, picture the corners mitered with no end grain at all like this one has and contrasting colored splines.
This is Ash with 15° walnut dovetailed splines having a 1° taper.
The 1° taper is the key to getting them tight. And they are tight tight tight. Tap them in too far and they will split the wood. No need to mix up any goop to cover cracks cause there will not be any.

[GareyD]

If ya need to park a truck on that table, keep all grain running the same, miter the ends and put about 3 - 1/2" beadlocks in each joint....keeps the joint from moving and adds a ton of strength...the round edges on the beadlock has more glue surface than square floating tenons

Beadlock Kit

Just another way to do it  ;)

GareyD