Thank you for the idea of making your own cleaning "tap". Problem on it is that it seems all of the threads on a Bren Tripod are BSF. Well walking out to my garage might produce 500 to 1,000 different bolts they are all in either SAE or Metric system. BSF threaded items are not common over here in the States. Of course might be in someone else's garage.
Well like I said I'll try to pop up a mk1 Tripod pic with the BSF thread sizes on it as I have found them.
Later 42rocker