Joinery Question

[Matt Meiser]

My second youngest brother is getting married in the fall. My parents started a tradition of buying each of us a piece of furniture as a wedding gift, but my mom came up with the idea of having me build the piece. My brother has a degree in Industrial Design and took a lot of furniture design classes as well, so he designed the piece, I'm building it, and my parents are financing the operation. It is time to get started as it has to be done in time for my future sister-in-law's move to join my brother in Minneapolis mid-summer.

The attached picture shows the buffet he designed. It is not to scale, but is 66" long, 30" high, and 18" deep. The top and bottom will be 1-1/4" thick and the vertical panels that form the ends and the dividers between the door sections and drawer section will be 1" thick. The piece will be solid mahogany, with the exception of the back panel which will be 1/2" plywood. I'm trying to figure out how to join the top/bottom to those vertical panels. I'm particularly concerned about the top because I know that people will try to move it buy picking up on the top. I've come up with a few ideas, including biscuits, loose tenons, stopped dados, and sliding dovetails. I'm worried that the first three might not be strong enough, while I'm worried about being able to pull off the last one--in particular, I'm concerned that a 17" long sliding dovetail would be very difficult to assemble due to friction. I've never done a sliding dovetail before. My Leigh jig is supposed to help create sliding dovetails.

One other option, which would have to be approved from a design point of view would be to use a combination of biscuits or stopped dados and screws. If I did that, I'd create square recesses for the screws in the top and fill with square plugs, possibly of contrasting material.

[Steve Cox]

What you're looking for is a tapered sliding dovetail joint which is meant to address the very concern about friction you have. There have been a number articles over the years on the joint. I have one in one of the "Fine Woodworking on..." series. It is the one on "small shops" and is in an article about making a tool cabinet. I don't know if your Leigh jig will help with that.

[Lamar Horton]

You could rabbet a top and bottom panel flush with the top and bottom of the side panels and then add the top and bottom pieces using screws. Also furniture should never be carried by the tops.

[Alan Turner]

While it would require design approval, a series of through wedged M&T joints would be quite strong, and could end up as a design element as well. Perhpas ebony wedges?

Another way to do it is to use several 3" or so wide strips on the top, half blind dovetailed into the sides, and then the top would be screwed on from underneath, through the strips. This is pretty classic carcase construction, but again would require design approval as it would add 3/4" or so to the height.

[Mark Singer]

I would use a sliding dovetail or dado at the bottom....at the top use a sub top which is essentialy 2 strechers . I typically dovetail those at the last vertical panel , where it croosses the oter panels use dowels or screws. That allows you to make the top seperately and add to the cabinet while complete. The front strecher can be set as a door stop...set back the thickness of the door. If you set the verticle panels in the dados in the bottom the strechers and back will "plumb" the panels and maintain square....This is an easier design technique and will reduce problems.

[Doug Shepard]

I get the sense that you're wanting to stick with traditional joinery, but one other option that comes to mind is pocket screws. They'd be out of sight inside the carcase. Just a thought.

[John Hart]

I would have to second the pocket screws. Very strong and assembly is simplified.

[Tom Jones III]

I built a couple of bookcases that were rather tall and wide. I wanted to make sure that the carcase was strong enough so a couple of the shelves are attached with a sliding dovetail of about 12-14". It didn't really need glue but I put it a little yellow glue and it acted like a lubricant. It worked great and I really appreciated the extra strength.

[Matt Meiser]

I emailed my brother to get his opinion. He really likes the idea of the plugs so I mocked up a piece to show him. I will probably end up doing this even if I don't have to. Also in the picture is a knob like the ones he designed for the piece. We talked about ebony, but I think we are going to go with maple colored black with india ink.

I'm nervous about my first project with sliding dovetails being in such an expensive wood so I'll probably either go with something like Mark suggested or go with the screws.

BTW, the finish on this is Trans-tint dyes which I'm trying for the first time. I think I'm going to like them. I put one coat of oil/poly mix over that just to give them an idea of what it will look like. Final color matching will be done in a few weeks when my future SIL brings down a leaf of the dining table she already has.

[Matt Meiser]

Also furniture should never be carried by the tops.

No, but at some point, someone will try.

[Jim Becker]

Matt, I like! Very nice. That's gonna look wonderful! I used the inlayed fake through tenon technique on the LCD TV stand I made awhile back. The angles would have been challenging to do real through tenons in that piece.

http://www.sawmillcreek.org/attachment.php?attachmentid=6268&stc=1

BTW, walnut ebonizes very nicely with india ink and in some respects is a nice "poor man's ebony". But you can use just about anything. Scrap cherry might also be good and it will absorb the color better than the maple.

[Alan Turner]

Matt,

Don't know what your tooling is, but you can pretty easily find single wide planks of at least 5/4 mahogany for this project. Just a thought. Should be in the 9-10/b.f. price range, and you can get it long enought to end grain match the top and sides. If you buy it a bit wider, you can also get the front edge of the bottom and the three aprons from the same plank.

If you go with the screws, plugged, you might consider mortising in a piece of mahogany where the screw threads will be seated as a screw into end grain has less strength than into long grain. These would be inside the carcase and so not too visible.

Note that the side aprons are cross grain to the slab sides, so you will need to accomodate the wood movement in this aspect of the design in terms of attaching the leg and apron structure. Slotted holes up thorough the bottom of the side aprons will work for this, with single holes on the front which will hold your reveals firm.