09-11-2019, 01:13 PM
(This post was last modified: 09-11-2019, 01:52 PM by Tony Griffiths.)
(09-11-2019, 08:40 AM)Ian Williams Wrote: Why not machine it to the same thread as original Tony? Any good turner can measure the tpi and diameter to achieve that.I agree, and, a good, competent turner could manage that - but perhaps his friends did not realise when (perhaps) testing the thread with a thread gauge, that the thread angle is 55 degrees, not the usual American 60 - and this caused some confusion as the gauge did not fit correctly? However, we are dealing with a large-diameter, shallow thread and getting that spot-on as a one-off is not easy; I wonder if the American machine shop he tried had access to a Zeus book that should give all the necessary tolerances, etc.?
I've no idea if the diameter is a "standard" or something made as a one-off by Austin - here you can see why it might be a little complicated....
A modern replacement for the Zeus book is the Hague App for the iPhone, though I've not tried that yet, it probably doesn't have BSP dimensions - and would hardly be as handy in the workshop. I wonder if this chart of tank fittings might help - or even one of these as a temporary fitting - or scroll down this page for brass-collar screwed fittings.