Skull screws

Skull screws are used for 2 basic functions, to provide mechanical stability to the drive, and as ground/reference electrodes.
For instructions for fabricating the ground screws, see the relevant page in the drive building instructions. 

In order to minimize the space taken up by screws, as well as the impact on the animal, small screws are preferable. The most important parameter though is that the thread diameter must match the diameter of the drill bit used to make the burr holes. We got good results using a screw thread diameter of 6.5mm for #1/4 round carbide dental bits (0.5mm OD).

Currently the best source for these screws seems to be watch maker supplies, and most screws are not stainless steel, so get in touch if you know of a good source!