SASM wrote:2.) The holes for the sliders are milled and of course you cannot mill sharp "inside" corners. A few other areas are milled, too.
There are a number of ways to make sharp corners for a thru hole like that. Being a former toolmaker, I have done both of the two most common.
First possibility - broaching. A broach is like a precision file that gradually gets larger, until the last teeth cuts the final shape to size. Many car parts are broached to fine finish dimensions - e.g.the smooth pockets where a universal joint gets bolted onto a cast(hot forged?) iron driveshaft end. Broached, not ground. You can even do broaching using a manual arbor press if necessary. Mechanical watch dudes broach many holes to final size.
Second possibility(totally being done back then) - electro discharge machining(EDM). You grind a solid carbon blank to .0015(english/standard) smaller on all dimensions than your holes and the machine can burn precision holes burn through that material in 5 minutes. Faster if already roughed in. I was the (sorry if offensive) "carbon nigger" for the shop I was at for a few months. Finally had to threaten to quit if they weren't going to rotate people. It is such a messy job -imagine grinding pencil lead into complex presicion forms all day.
EDM is extremely cheap today, as it has been surpass by other technologies.
Answer to question - yes, you can cast stainless steel. I would agree that some of the cases are poorly cast and angles are frequently off or different sizes. Again, I think some poor slob was expected to clean off the casting scale and they chopped those angles on top and at other placed to saves cases that wouldn't make the cut otherwise. I have to wonder if Roger senior didn't supervise or otherwise handle the finish machining of his cases.....his sons have told me he liked doing a lot of his own machining on watches and other things. Not many people know the RR had a business that ground out and refurbished brake drums. Or that he dabbled in machining his automatic transmission valves bodies for different performance/function.
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