Home made Boards

sbray said...



I built a rocker table along the lines of the Brokite table with both male and female jigs to form the mould surface and found that it was quite harder to get accurate lines than I thougt it would be

www.boardbuilders.co/2011/01/rocker-table-pt-3-construction.html

One thing I found tricky was getting the amount of concave correct. Because the top part of the table makes accessing the board a bit more difficult you end up needing more working area arond the board which means the distance from the edge of the board to the jig is larger than the distance you need if you are just using female jigs and nailing/screwing the table surface to it.

This means that to get the amount of concave accurate you need to work out how much the surface of the table will continue to curve in the space between the edge of the board and the jigs. You need to know this because you need to know how much deeper the curve in the jigs should be than the centre rockerline jig that creates the concave. I got this really wrong and ended up with half the concave I'd designed in. I later found out how to estimate it better (see link above and go to 'what went wrong'.

The tables that I have subsequently seen that look like they work well are ones that use two different surfaces. The first in usually 3/8" marine ply or MDF that is fixed at the center edges and bent up at the tips to get the right rockerline. Then a strip of, say, 5-10mm wood in placed along the long center line for about 2/3 of the length and is usually tappered off at both ends. Then a second surface (1/4" MDF, malomine coated chipbaord or masonite, laminex or perspex ) is then laid over the top of this the edges fastened at the edges to the surface below. This way you have a lot of real time control of the rocker and the concave. You can even use clamps along the edge of this to flatten the center section to get 3 stage rocker. The beauty of this is that it is adjustable real-time instead of having to cut new jigs and you can tweak it to get exactly what you want.