On 13/04/2021 09:52, wrote:
Hi all,

Firstly thanks very much for all the info on the other thread. Study
now designed so now in build phase

I have cut the pieces for the first cabinet out of 18mm ply so now
looking to put it together. It is 900mm wide (500mm deep) so
wondering what the best way to glue/ screw it all together to make
sure it is square. I have done some searching but they seem to make
it up first them adjust it. I had anticipated using fairly decent
screw lengths (say 60mm) so thinking that it would be very rigid (and
heavy) so ability to adjust this way would be somewhat limited.

A screwed butt joint will not be so rigid that you can't tweak it later.
With cabinets it's usually simplest to rely on the back doing the final
squaring.

I would be tempted to assemble the 4 sides of the box, with glue and
screws (although with a butt joint, the glue will offer little
additional strength over the mechanical fixings). Then measure across
the diagonals and check they match. If not, stick a clamp corner to
corner on the long diagonal, and tighten until both diagonals match).

Leave it to dry, and then remove the clamp - it may spring back a
little, but not enough to worry about.

Now stick a rebate round all four back edges on the inside[1] - say 1/2"
deep and wide. Cut you back from 1/2" material, and make sure that is
really square - set the dimensions so that it is a snug fit into your
rebate. Tap that into place and fix (glue alone will be more than
adequate here, but some screws will make it easier to ensure it pulls in
tight to the back.

[1] or do it on each piece before you assemble

Also,
I was planning on having a fixed shelf in the middle to add further
strength (and in reality we never change the height anyway) so this
would further impede this approach.

You can fit the shelf after if you are screwing through the sides. If
you are setting it into rebates/dados then it does not need fixing at
all, since it will be captive after assembly.

Any ideas how best to go about it?

If you want to avoid the routing phase, then you can just cut the back
to full width and height, and plant it on the back (although that might
be visible from the side)

--
Cheers,

John.

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