B25 Oil switch thread - tapered or not?

[MadPete]

The new oil switch I have ordered in looks like it has a tapered thread. The broken old oil switch I removed may well have had a parallel thread. It didn't leak when the engine was last running.

What thread should the oil switch have - parallel or tapered? Does it matter? (I suppose a tapered thread is required after previously fitting one)

[V500]

As I recall BSA never fitted any taper thread fittings at the factory, but I have come across a couple of US imports where a taper thread has been forced in, and in one case this taper thread had cracked the area around the switch.

[Rupert]

Oil pressure switches were produced with two types of thread, tapered or parallel, the latter had a copper compression washer for preventing oil leaks rather than relying on the tapered thread for sealing.
The female thread in the inner timing cover is always parallel threaded  not tapered.