Ah, yes, machining back then was an art.
One company made the housing for an equipment out of pieces of balsa wood glued together to establish the best shape before using that to generate a precision casting.
Many parts were cast by the lost wax method and then finished by hand.
I can recall making a replacement part for our home ice-cream scoop (quite complex with gear teeth on it) by filing it by hand.
One of our first apprentice exercises was to file a rod of arne (very hard steel which work-hardened much harder) by hand to an exact inch in length and exactly square. Amazing just how accurate that had to be so that a set-square placed on end and side did not show the faintest glimmer of light. I was first out of our course to finish, exactly right, dead square, absolutely perfect, but, as Mr Derek Wilkinson was quick to point out, exactly 1.100 inches long. I spent hours getting that down to the required 1.000 inch.
There were a lot of cunning techniques for making better and better machines. In fact, one of our tasks was to make on a really grotty old lathe jobs which the better lathes could knock out in seconds. That sorted out the men from the boys!
One of the most spectacular jobs I had to do was to machine a great ingot down on an Ormerod shaper. This had a to-and-fro action, and, if you came in carefully from the side you could work up to enormous cuts taking great swathes of metal off, which when dosed liberally with cutting oil, left great smoke trails across the model shop. The next lad took over from me and enquired what cuts to take. I told him I'd been doing half an inch by fifty thou. Didn't expect him to start right in the middle of the workpiece. The shaper drove the tool clean into the piece, the Ormerod stopped dead with a broken carriage, and took the workshop floor up like a good-strength quake.
