LBSC – Why?

[Speedy Builder5Participant @speedybuilder5]

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

[bernard towersParticipant @bernardtowers37738]

the core dia for 3/16 x 40 is larger than 2ba and 40 tpi is good for bronze, perhaps thats the reasoning ?

[DurhambuilderParticipant @durhambuilder]

A fine thread is less likely to self undo than a course one. As the nuts are only tightened against spring pressure and constantly ‘rattling’ might they might self loosen with a coarse thread?

[Speedy Builder5Participant @speedybuilder5]

Only by 0.0025″ Bernard. I do agree with Durham builder though.

[Author]

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