Dear dialling colleagues, I'm helping to restore a Richard Melville (worked 1832-1871) slate dial with multiple gnomons. The gnomons are held in with 2BA brass screws using square nuts. The gnomons themselves are nominally 1/4 inch thick but with considerable variation, i.e. not the modern rolled plate accuracy.
Can anyone tell me when the BA (British Association) screwthread standard started? I think it points to the gnomons being (old) replacements. Regards, John Davis ------------------------------------- Dr J R Davis Flowton Dials N52d 08m: E1d 05m -
