Essentially the torsion box top is made in a similar way to others you may have seen on the internet. I made mine from lightweight 12 (1/2") nominal MDF, oak and hardboard. I started by cutting an 8' X 4' sheet in half.
The resultant sheets were then cut to 1220 mm (4') x 1150 (3'-10") mm. I then cut a number of 50mm (2") wide strips from another board.
The cut list for the strips was this:
- 2 off 1220 x 50 x 12 - (4' x 2" x 1/2" for the front and rear outer sides
- 5 off 1196 x 50 x 12 - (3'-11" x 2" x 1/2") for the inner dividers
- 2 off 1125 x 50 x 12 - (3'-9" x 2" x 1/2") for the left and right sides
- 42 off 189 x 50 x 12 - (7-1/2" x 2" x 1/2") for the spacers
|Initial glue up|
I did this all the way across staggering the segments as shown in the picture above and then glued the top and bottom sides into place.
|Gluing the top panel into place|
I then cut a number of scrap pieces of wood and glued them inside the outer sides to enable screwing the oak trim boards into place. The scraps were a mixture of hard and softwoods and were just what I had in the burn box.
The dimension for the final spacers was measured to allow for the cumulative error that inevitably happens in such a construction. Those spacers were cut to this dimension and glued/pinned into place. The rear outer side was glued/pinned into place and the whole construction left to setup over night.
Next day I made sure all the transition joints were level and glue free by running a block plane over where necessary. Glue was then liberally applied to the edges of each spacer/divider and the top panel was dropped into place. To reinforce the joints and aid clamping the top panel was secured with 18G brad nails. I was careful to measure the position of the nails as a future procedure is fitting the removable hardboard top with screws. I didn't want to hit a nail with the screws.
I then cut a sheet of hardboard to size and screwed it to the top with a regular hole pattern designed to miss the brad nails. Once the top had glued up I used a flush trim bit in a router to clean it all (including the hardboard) up to size. This was repeated on the bottom board too.
The trim boards for edge protection were cut from some leftover oak flooring that a friend had given me. These were brand new but had grooves cut on the underside. I guess those grooves are to stop the boards warping when put down. I milled the boards down to remove the grooves and they ended up around 14mm thick (9/16"). Then I ripped the tongue/grooves off and cut the boards to width and length. Then it was a simply matter of screwing the boards to the torsion box table top with long screws. As I had taken the time to glue real wood to the interior this made for a secure connection.
The boards were then flushed up to the hardboard top and the whole lot was finished with some external polyurethane varnish I had left over from a previous job. I applied 4 coats all over.
The table top is extremely rigid and is flat enough to assemble furniture. It is also relatively lightweight so can be stored out of the way when not required. I have sat it onto my modular saw horse which is phenomenally strong despite it's looks.
|The modular saw horse base|
|The finished low assembly table|