Wide Board Mahogany for a Table Top

Forget the "ripping and flipping" myth — just use good joinery and the right supports. March 26, 2009

A customer of mine, recently, bought two slabs of 4/4 26" (yes, 26”) wide board about 16 foot long each of Honduras Mahogany . He wants to make a dining table using these two slabs. I understand that I need to take care of warping, cupping and crack. I have read and been advised to rip it and joint them back together with alternating “cup” pattern. I told him that, but he doesn’t want to do that, for he wants to keep its grain pattern.

What do you think if there is anything wrong to do as follows:
1. Route several dovetail slots, don’t know how many yet, across the grain on the underside of the table top.
2. Make some long “dovetail pin” that would fit in these dovetail slots.
3. Glue these bars to the dovetail slots.

Thank you for your advice.

Forum Responses
(Furniture Making Forum)
From contributor D:
What will the understructure of the table be? A conventional 4 (or 6) leg design will allow for several cross members to tie the two long aprons together. A small plow in the cross members, as well as around the upper aprons inside, will allow the use of wood clips to hold the top and allow for expansion. The top also can easily be removed for future refinish, moving, etc.

Do not fasten or glue any wood cross grain to these boards - that would be the biggest mistake you could make. Float the top on a nice sturdy frame. Join the two boards for grain, forget the mythological cup up/cup down unless you are putting this outside. 8/4 x 3-1/2" aprons would do it.

I would not attempt trestle table or slab table with 4/4 boards. Perhaps a two/three pedestal table with a decent support frame. In any case, determine the moisture content of the boards and insure it is correct. If not, explain to your customer that he is now a gambler, but you are still just a woodworker. You don't want to gamble with his wood.

From contributor U:
Remember to state that there is no warranty with regards to cupping and cracking. A note on Honduras mahogany - isn't it illegal to sell mahogany harvested in Honduras within the United States?

One of my suppliers told me that the price of mahogany is high right now (compared to last year) because there has been some 'paperwork' issues with some illegally cut lumber in that region of the world.

From contributor D:
All Honduras mahogany is sold within the limitations of a CITES class 2 agreement. This controls shipments from country to country and is a way to insure legal timber is shipped. Due to international pressure and problems controlling illegal logging and bureaucratic bungling, Brazil is not currently exporting mahogany, so almost all coming into the U.S. is from Peru. It is possible to monitor legal vs. illegal cuttings from space with satellites, and Brazil apparently feels violated. Supply is very tight and prices are high.

As I understand it, very little comes from Honduras. It and neighboring countries have already been heavily 'harvested' and do not have much to export in mahogany.

Contributor U - you may be thinking about rosewood and its restrictions. Brazilian rosewood is the species that is now illegal to transport across international boundaries. So when the people from the overcrowded cities in Brazil take up the government's offer to become subsistence farmers, they end up out in the jungle and burn off their 10 to 20 acres. Used to be, if there was a rosewood log, they'd haul it out and get $25 for it. It would end up on the world market at market price. Now, with the export illegal, they just burn it along with all the other trees 'in the way.' Logging is not a pretty scene anywhere, but represents less than 20% of the deforestation in Brazil. The rest is all agriculture, from subsistence farmers to huge international conglomerates farming everything they can. A Chinese company is the biggest rice grower in the world, all in Brazil, all on recently cleared land.

There have been examples of enthusiastic customs officials seizing musical instruments and such, for their rosewood content. One must now have documents stating that the rosewood was cut before the international CITES class 1 ban to move from country to country.

From contributor M:
Thank you for the advice contributor D. I will have the table top float. He got this wood from a boat builder who has them for years and now they are no longer in the boat building business, so they sold them.

From Gene Wengert, forum technical advisor:
The idea of ripping and flipping has little or no validity. The key is to get the table top at the correct MC before you make the top. The correct MC is the MC that the table will have in use. In this way, the changes in MC after the table is built will be small and if these changes occur slowly, there will be little warping issues. Slowness can be assured by using a moisture vapor-proof finish, top and bottom.

From contributor W:
My father made a similar table 40 years ago and it is still as flat as a pancake. The boards he had were 42" wide and 16 ft long. He had to cut the boards to 36" wide because he could not find anyone with a planer wider than 36" at the time. He was very careful to finish the top and bottom with the same amount of finish. There is no apron on his table; only the slides underneath.