Bosch drill battery adapter

After the original NiCd battery packs on my Bosch drill finally died, the drill was left in a corner to gather dust since new battery pack would cost almost as much as a new drill. I designed this adapter to allow me to use my Ryobi Lithium-Ion pack to give the old trusty a new lease on life.

The design consists of two main parts, the Bosch adapter and the Ryobi adapter. This will allow me to later replace the Ryobi adapter with a custom battery pack (when I get around to it).

Some extra materials required for assembly:

+ 3 x M4 screws (20mm and cut to length)
+ 3 x M4 nuts
+ 2 x 1mm Brass shim 12.5mmx68mm (you could probably use a piece of 0.8mm copper clad for this instead)
+ A coil spring approx. 8mm dia and approx 70mm in length. A shorter spring can be used, see below
+ Two short pieces of 7-8mm rod to make up the total length if your spring is < 70mm
+ Some more 1mm brasss for the Ryobi adapter contacts
+ Wire

Assembly should be fairly straight forward usin