First I make a small pilot hole (in this case 1 mm).The PDB (Power Distribution Board) is the central piece in the load-bearing construction. The arms, the landing gear and the camera gimbal all attach to the PDB. It is also a PCB with intergrated copper tracks for powering the motors (via the ESCs) and other electronics. There are prerpared solder pads for the battery connector and the six ESCs.
I need to make holes in the PDB for fastening the gimbal and the retracting landing gear. Making holes the the PDB is not something to be done lightly. If a screw short-circuit the two sides it will ignite the battery. So, the copper must to be removed around the holes to create an insulating buffer around the screws.
First I make a small pilot hole (in this case 1 mm).
Then I use a cutting compass to cut a circle in the copper.
After that I carefully remove the copper inside the circle with a small chisel (a small knife would work too).
The hole is then enlarged to 3 mm and still has a good 2 mm margin between the M3-screw and the copper.
To hold the cables to the ESCs firmly in place, I have cut two recesses on each side of the arm mounts for cable-ties. The recesses should be rounded, not edgy, because sharp corners create tensions that eventually can break the PDB.
The cable should be fixated with the cable-tie and some rubber-foam before soldering them in place. The cable-tie then holds the cable in the position it was solderd. Trying to fixate the cable after soldering is difficult and will create tensions, especially if some tin has crawled up inside the insulation making the cable stiff.