I have a 20mm plywood board that measures 550mm x 120mm. I would like to drill a hole all the way through the side of this board which is perfectly perpendicular to the side edge and parallel to the front/back faces:
I have picked-up a drill bit that is of sufficient depth to clear the 120mm. I have done a trial run of the hole twice, the first one was not perfectly parallel, but within tolerance. My second attempt failed miserably and ended up drilling through the front of the board.
The problem I am having is keeping the board parallel to the fence. Despite clamping the board to the fence, it is much shorter than the board and I am finding there is far too much play on the top of the board.
You can try clamping to a right-angle piece.
We have a big (massive) right-angle fixture in the metal shop that could work, depending on the size of your piece.
A couple of clamps to the piece and a couple to the right angle plate and you are all set up.
I will be at the space this weekend, if you are in, give me a shout and I can point you in the direction of the fixture in the metal area.
