I know he sent me one on nipples which was very interesting but can’t recall any on screw samples. I will ask Jim, thanks.
Yes, early doors they did make their own screws, I apricate that but as you say that was before standards. As the Birmingham gun quarter expanded during the mid 1800’s as you know it became a workhouse of hundreds of small businesses for the out source of parts, Action filers, Stockers, Barrel filers, Lock makers, Engravers, etc. etc. Now all these bits had to come together at some stage so some type of standard had to have been used or it just would not have happened.
It used to be easy for me as any screws I needed (if I had a sample) it was just take it into work, put it on the shadow graph and measure it, then make one to match. Items with screwed holes in them were a different matter, as most times I had to make a tap to suit them, still have some of them. It is far easier to screw cut a round item than it is to screw cut a hole, purely based on the clearance needed to work in relative to the space required to do it, this is where taps come into there own.
A typical problem is new extractor pins on decappers, their sizes are very odd as are the roll turn-over forming dies to fit an Excel machine. As I make so many of these I actually had taps made to suit but they are not very cheap in fact a set of made to measure H.S.S. ground taps are very expensive and although the mating thread is of Whitworth form in the main they are always oversize on the root radius of the thread and I find it best to run a die down them just to clear out the bottom of the thread.
As John said an interesting subject.