"Andy Dingley" wrote in message
...
On 29 Nov 2004 19:23:01 -0800, (tillius)
wrote:

(snip)

You'll also be wanting a biscuit jointer. It's just the best way to go
about MDF carcassing. Rebated laps if you want some positive location,
but go for those biscuits. Screws just don't work. For the "short
grain" problem, neither do lock mitre bits.

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Screws can work, but one has to take into account the nature of the material
and the effects of gravity. I use a Trend pocket-hole gizmo and it works
well. There are caveats however. If the screw is used as a fastener it will
work, if it is used to bear a load it will likely fail. If you use the wrong
screw the MDF may split, if you use the right screw in the wrong place it
may split. If you screw into an edge without the appropriate pilot hole it
will likely split. If you don't use the correct stepped drill for
pocket-holes it will split. Once one takes all that into account
pocket-holes will let you make things out of MDF without hassle, except
one....lining the parts up. So I agree with you that rebates and dadoes will
save a great deal of clamping effort and ensure proper line up of parts,
(the pocket-hole joints will try and move as you tighten them). I'm going to
practice a little with first 1mm and then 2mm dadoes to see what works best
for me.

Regarding the OP's query I would say that MDF is quite adequate but I would
use 22mm for the top and 18mm for the rest and I would use pocket-holes to
fasten it all together.