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Don Abele
02-19-2004, 10:51 PM
I am getting ready to make a new kitchen table top. I will be using 4/4 maple glued up to a total size of 32x46. I will then wrap the whole thing with 3" of walnut with the short ends being across the grain and the corners mitered. I am also planning on flipping the edge (with a 45* cut) so there is no edge grain showing. Follow me so far? :)

OK, so...with the breadboard ends against the grain, I was going to use a mortise and tenon joint pegged from the bottom with the outside couple of inches glued. Is the tenon the same size as the mortise or smaller to allow movement within the mortise?

And...with those mitered corners, I'm pretty sure that if the maple field swells across the grain, they are going to open - any ideas?

This is my first table top like this, so advice is welcomed and really appreciated.

Here's a quick pic that hopefully visualizes it better (sorry but I'm no Todd when it comes to SketchUp, I'm still trying to watch all those videos). This took like 30 mins to do :p

Thanks,

Todd Burch
02-20-2004, 1:50 AM
Doc, the miters will certainly open up, as the maple will expand and/or contract.

I've attached an image of the traditional method for breadboard ends. Like you mention, it does allow a small section of end grain to be seen, although it is slight.

Your approach for the tenon is correct. I would make the tenons at least 1¾" long, 2" might be better. A tenon any shorter will make putting a reasonable sized dowel in it frustrating, as there really won't be enough long grain between the dowel hole and the end of the tenon. (For example, with a 1" tenon and a 3/8" dowel hole centered on the tenon, that only leaves 5/16" on either side of the dowel.)

If you use plywood for the field, and veneer maple to it, you will be fine with the mitered corners, but then also you don't need the tenons.

Another option, to keep the mitered corners and still have a breadboard, would be to miter the ends of the breadboard and glue on a "return" (like you would "return" a piece of crown or base moulding). If you need a picture, let me know. This way, you would have no end grain showing, and the maple, with 3" walnut glued to both long sides, could still expand and contract in the traditional method. The difference here is that the breadboard ends have mitered and returned corners instead just end grain.

One last thing. On a breadboard end, you want to glue the middle, not both ends. If you glue the outside ends, your top will surely split.

Todd

Michael Cody
02-20-2004, 6:37 AM
I am getting ready to make a new kitchen table top. I will be using 4/4 maple glued up to a total size of 32x46. I will then wrap the whole thing with 3" of walnut with the short ends being across the grain and the corners mitered. I am also planning on flipping the edge (with a 45* cut) so there is no edge grain showing. Follow me so far? :)

OK, so...with the breadboard ends against the grain, I was going to use a mortise and tenon joint pegged from the bottom with the outside couple of inches glued. Is the tenon the same size as the mortise or smaller to allow movement within the mortise?

And...with those mitered corners, I'm pretty sure that if the maple field swells across the grain, they are going to open - any ideas?

This is my first table top like this, so advice is welcomed and really appreciated.

Here's a quick pic that hopefully visualizes it better (sorry but I'm no Todd when it comes to SketchUp, I'm still trying to watch all those videos). This took like 30 mins to do :p

Thanks,

Why not make the top out of birch ply & veneer it .. that would solve a lot of your movement issues -- if not birch ply, (yes I said it) MDF core ply... but I still suspect your mitres would open but you'd have a lot better chance that way.

Mark Singer
02-20-2004, 8:02 AM
Doc,
Some time ago,I posted a table of solid wood designed for movement which was bigger tham what you are proposing ...I have had no problems and it is attractive. Here is one picture and the link to the thread:

Be sure you check my thread it explains movement in a large solid wood table and how to design for it.
http://www.sawmillcreek.org/showthread.php?threadid=5510

Robert Ducharme
02-20-2004, 1:06 PM
I see all these items about wood expansion and sort of understand why it happens. How does not tell how much expansion can be expected for a workpiece of a given size, wood type, or combination of wood types. Are there any definitive reference books to help in this area?

For example, I will be making bench tops all made from soft maple cut with endgrain up but the total length will be 39" x 18 feet. How much can I expect that to expand, where at, how should I attach it to the cabinet tops, what should they be finished with to reduce expansion?

Would this be worth putting in a separate thread and getting the answers there?

Dan Mackley
02-20-2004, 3:13 PM
Would this be worth putting in a separate thread and getting the answers there?

Robert,

I'm not an admin-type, so I don't know if this is the right place to respond or not, but here are some links to get you started on wood expansion/shrinkage calculations:

Accounting for shrinkage/expansion:
http://woodworking.about.com/cs/plansanddesign/a/shrinkage01_p.htm

"Shrinkulator" calculation page for many wood species: http://www.woodbin.com/calcs/shrinkulator.htm

HTH,
Dan

Robert Ducharme
02-20-2004, 4:40 PM
thanks for the links

Steven Wilson
02-20-2004, 4:59 PM
You could consider another way - don't glue the maple. Instead, make your walnut frame solid (w/miters) and let the maple float in the field. Keep the maple aligned by a T&G joint. Each maple board can be pined to the walnut frame on the ends in the middle of each board and leave some room for each board to expand/contract with it's neighbor. Wood movement between any particular board would be fairly slight. Of course, the other ideas are great too, just wanted to give you another