I have finished a 5″ Gauge Speedy that was started by another excellent modeller. The drawings are all in imperial and generally uses BA threads and ME threads. The ME threads are for brass / bronze water fittings. But for the life of me I can’t understand why the sprung axle boxes have 3/16″ x 40 tpi studs connecting them to the suspension springs when 2BA – being a coarser thread could have been better used to thread into the bronze bearing blocks.
Was it because he had always used that on other models and just copied them ?
And a note for other SPEEDY builders, the above studs are too long and when you pass over switches (points) the end of the studs can graze the rail head – and why my discovery of the 3/16 x 40tpi thread question.
Bob