butt joint help needed

[Mike Gager]

im in the design stages of a small table and ive run into a problem i need some help with. im trying to figure out the best way to join 2 boards that would have the most structural support

what im working with is i need a board to join perpendicular with the apron of the table. the top of the table will be attached to this board (there will actually be 2 of these attached to aprons on both sides)

anyways heres what im talking about

joint.jpg

just a simple butt joint more or less. the problem is i dont want any visible joinery so that rules out pocket screws, through M&T, through dowels, dados, sliding dovetails, etc. and leaves non through M&T and dowels, biscuits, and i cant really think of anything else

my thoughts on the dowels and M&T is the aprons are only 3/4" thick, is that enough material to make a solid connection without poking a hole in the side? with the M&T will that weaken the strength of the aprons? they are the support for the legs so if they are weakened the legs may be wobbly. biscuits dont seem like they would add enough structural support but i could be wrong

are there any other options?

[Jamie Buxton]

The trouble with a biscuit in this joint is that it is aligned the wrong way in the board which is the top of your T junction. The biscuit's slot in that board is essentially a crosscut. That is, the faces of that slot are end-grain. Glue faces on end grain are not as strong as glue faces on face-grain.

I've used dowels in joints like that. With them, you get at least some face-grain to face-grain gluing. For me, the challenge with dowels has been to align multiple holes in both pieces of wood. One solution is a shelf-pin jig. These control a plunge router to make a series of holes which are in a line, and some exact distance apart. Put one series of holes in one of your pieces of lumber, and a mating series in the other piece of lumber. You can get shelf-pin templates with holes on 1" centers, and use a 1/4" router bit. That will give you a fair amount of wood sewing the two together.

[Bill Geyer]

The only joint I can think of to meet your needs is a French (sliding) dovetail. It's strong and will provide the glue surface you are looking for.
It's pretty much invisible, but you will know you did it right (remember Nakashima's statement about good joinery being an example of "unseen morality".

[Dan Blackshear]

I'm assuming a glass table top hence the non visible joinery, but how about a stopped sliding dovetail cut from the bottom of the apron?

[Tom Veatch]

Stopped sliding dovetail - machine from the bottom, stop short of the top, endgrain gluing in apron, but joint strength not fully dependent on glue.

Dowels - drill holes in end of cross piece, use dowel centers to locate stopped holes in apron. User brad point bits to get maximum depth without penetrating outside surface. Optional metal "Tee Plate" inlet into the bottom (nonvisible side) of the joint.

Wouldn't use M&T - endgrain gluing surfaces

[glenn bradley]

+1 stopped sliding dovetail.

[Todd Burch]

Stopped sliding dovetail - machine from the bottom, stop short of the top, endgrain gluing in apron, but joint strength not fully dependent on glue.

+1, but I would start from the top and stop short of the bottom. That way, once the top is on, there is no visible joint, and, in the event of glue failure in 30 years, the stretcher won't fall out.

[Mike Gager]

well the top of the aprons will be visible so doing a sliding dovetail from the top isnt what im wanting however from the bottom may work as the only way to see the joinery would be to look underneath

i had considered a sliding dovetail before but thought it might compromise the strength of the apron but really i guess once its glued the strength will still be there. how deep of a groove should i go for in 3/4" stock? i was thinking 3/8" sounded ok and would still leave plenty of material. shuld i go deeper?

[Lee Schierer]

How about using a blind wedged tenon joint. The mortice is cut with dovetailed sides. The tenon gets two wedge cuts and two small wedges. You apply glue in the joint, place teh wedges in the starting slots, place the tenon with wedges into the slot and tap it in until the wedges fully seat locking the tenon in place.

[Thomas Pender]

+1 on Sliding Dovetail

When I do a stopped sliding dovetail I usually work with a few scrap pieces until I have what I want, e.g., the feet on a hall tree, the sides on a drawer, whatever. It can be a bit finicky but I agree totally with everyone else that says it is the way to go.

Oh - you can build a jig for your router table that will really help you cut the dovetail sides - just a larger piece of finished or waxed 1/2 plywood with a rectangle cut in it that exposes the dovetail bit and it is clamped to the fence. You can use paper shims to adjust the fit of the jig board away from the fence. Also, I have found when I cut the stop to use a stop board clamped in front (or back) of the bit so I know exactly where it will end and it makes it repeatable. I also use a 1/4" straight bit before using the dovetail bit - less burn, tear out, you name it.

Uusually, you have to cut the slot into the receiving board a tiny bit smaller than the sliding dovetail, but I have met guys who get a fit that astonishes me. As a rule of thumb, you do not want to have to force it too much, but a little snug is OK. Goal is to be able to slide it in and out buy hand - not with a hammer, but be prepared to do that once you apply the glue and have a nice piece of plywood handy to spread the force of the mallet - will keep marring down. You certainly do not want the dovetail to wobble as some of mine have from time to time.

Oh - do not be ashamed if you have to use some Timbermate, etc., to fill in on the sides - just for appearance. I have had to do this and some real experienced guys can hardly tell because I use a damp sponge to achieve a flat finish and then stain it or whatever. But, my main caveat is to experiment - the more you do, the better the appearance and the fit. That being said, since it will be stopped at the top, that will help a lot.

The only other thing a I can think of would be to cut stopped mortises, like on rails, but I think the dovetail is stronger and much less likely to fail.

Good luck!

[Prashun Patel]

What's the overall design?

If you have the jigs for it, a sliding dovetail is elegant.

But dowels or loose tenons feel like the easiest solution. 3/4" is fine; go as deep as possible without punching through. If you dowel the entire joint - looks like it can accomodate 5 or 6, you'll have no problem with integrity.

[Paul Atkins]

Why don't you want any joinery to show? What type of top and how is it being fastened? A butt joint is a type of joinery and would be visible. The small sliding dovetail would give it a sense of unity and strength where a simple butt joint just looks like it is just placed there without any real look of connection. My 2 cents.

[Mike Gager]

its a floating top design so the aprons are going to be visible. the butt joint wont look any different then the mortise and tenon joints that will be used at the rest of the joints

[David Eisan]

Hello there,

Just use a biscuit, you will be fine.

David.

[Tony Bilello]

A simple dado and some inside corner blocks should be sufficient. This is not a new idea and I have had to bust many of these simple joints apart when repairing furniture made in the 1950's and older.
Many years ago I went to a 3 day workshop put on by Tage Frid. When asked which is the best type of joint, his reply was " the easiest one to make that will be sufficient for the job at hand.