Working on my 2001 Audi TT project car, I discovered that I needed to drill some holes into the chassis to replace two brake-line brackets that had completely rusted. To get the holes perpendicular to the local surface, so I could tap them, I built this prototype drill jig.
The drill bit is inserted through the two small tubes running away from the camera. The angled strip acts as a spring, so that bits of different diameter can be accommodated. The bit is held snugly so that, when the blue box is pressed to the surface, drilling occurs at 90 degrees, with almost zero deviation.
The spring tension is finely adjustable, using the two screws indicated. I toyed with using a strong magnet to hold everything to the surface, but in the end this wasn’t necessary.
This works surprisingly well (it was about the third attempt to build such a tool).
