Microswitches are an absolute pain to install and adjust, and maintain in adjustment. It is 10 times easier and more reliable to use a relay. You can get 10 changeover relays for under £3, such as:
All you then need is a simple on-off switch at the tie-bar or lever frame. Which is easily home made, using a bit of springy wire and a brass pin, or somesuch. The relay itself can be anywhere you like, and takes 5 seconds to install with a dab from the glue gun. You do require a 12v power supply for the relay coils, but it would be a strange model railway which doesn't already have that.
Thank you for your comments - much appreciated.
I was really looking for a solution that can be a self-contained physical addition to the point itself, mechanically switched by the action of flicking the point over. That's why microswitches attracted me; I am confident that I can devise a mechanical installation / actuating arrangement that can be mass-produced and rigidly attached to the underside of the sleepers.
Clearly, the microswitches that I am considering can be made to switch the polarity of the frog.
However, can the same microswitch switch the polarity of the switch rails, such that the there is not the possibility of the toe end of a switch rail being at the opposite polarity to the adjacent stock rail? (Thus allowing the free toe end to touch the back of a wheel flange and cause a short circuit)?
Furthermore, I ideally need the microswitch to determine which of the two diverging roads is live - ie. for the point position to activate the track to which it is switched; (though this function could be ascribed to separate section switches if it would significantly simplify the point polarity switching).
In summary, I wish to arrange matters such that merely changing the position of the point manually will :-
i] not rely on switch rail contact for electrical continuity;
ii] switch the polarity of the frog;
iii] prevent short circuit between stock and adjacent switch rail due to contact between adjacent switch rail and wheel / flange back
iv] ideally, but not essentially, switch power between the two diverging roads according to the point postion.
I strongly suspect that I will need something more complex that a SPDT switch, but something similar with perhaps more switched poles would be ideal.
Further comment will be very welcome.