@Paul Willis said:
One of the interesting recent developments in 4mm modelling is the Peco detailed bullhead fishplates. A simple google should produce plenty of examples, and suppliers.
Not only do they look reasonably convincing (more so if you have one of the pre-Grouping railways that ballasted well over the tops of the sleepers to hide the join at the bottom of the fishplate) but they are robust enough to use finctionally for pivoting straight switch blades. I certainly intend to try them out as a functional hinge when I next build some GER prototype pointwork.
The one thing extra that I will do is use wires to separately electrically bond the blade and rail, as I don’t trust the continued electrical continuity of a flexing hinge.
I would recommend that the blade and the closure rail on short switches are bonded together electrically. Make the insulated joints for the crossing at the crossing front joint and not between the blade and the closure rail.
This is not a problem with the lettered post-1923 switch designs, as one can use the switch heel joint instead and there is no risk of the wheelset touching two rails of different potential; it is, however, a potential problem with short pre-grouping- and industrial-style switches, as a wheel flange might touch the stock rail and the closure rail, which could be at different potentials. Well worth avoiding.