If you are somewhat experienced in wood working you can ignore this. If this is your first time installing one of these jack cups and the hole is not already in the cab panel, this article will be helpful.
Get your safety glasses on…
The best way to get the proper sized hole for your new wiring harness jack cup is to drill a pilot hole all the way through the panel with a 7/64” (0.1094”) or 2.7781mm drill bit.
Now get a 1 1/8” (1.0000) or 28.575mm spade bit, (do not use a forstner bit) and gently place and hold the very end point of the spade bit in the pilot hole, do not press down.
Now get the drill up to full speed (make sure the panel is held securely in place), and gently press down into the panel with the spade bit spinning at full speed. Gently ease the very tip of the spade bit down into your pilot hole. Start drilling out your jack cup hole until you have removed about half the depth of the thickness of your panel then remove the spade bit from the hole and disengage the drill.
Do not drill all the way through to the opposite side of the panel, doing so will cause tearing and splintering on the opposite side. You will want to flip the panel over and start over again Gently ease the tip of your spade bit down into the pilot hole and engage the drill up to full speed, start drilling out your jack cup hole until the spade bit meets the hole you previously made on the opposite side.
Following these steps will produce a nice clean, perfectly round hole for your jack cup.
Square jack plate dimensions