Ben wrote:
I'm looking at building a woodworking bench for myself and have
familiarised myself with the plans that are sold on the internet. All
the Kits and commercally availiable, ready built benches feature fine
lumber of 3+ inch thickness for the top - be it birch, beech or other.

Since I am operating on a smaller budget, I was wondering what reasons
are there why a sheet of plywwod - 3/4" or 1" oak or birch supported by
doug. fir (4x) lumber would not be used?

If you want a relatively low cost bench, built like a brick out house,
let me suggest the following:

Build a frame with doubled 2x6's, then covered with two (2) layers of
1/2", 4 ply, CDX.

Cover the CDX with a sheet of 3/4" MDF followed by a sheet of 1/4"
hardboard which is considered expendable.

Build the legs with doubled 2x6's, then bolt to the frame using 3/8-16
bolts, nuts and fender washers.

Angle brace the legs with 1x4's, bolted in place.

Keep it dry and it will be around longer than you will.

Lew