Last time I drilled the hole with the next letter size drill smaller than the ⅛” ball. Then drilled and tapped the back of the hole slightly larger to receive a set screw to apply adjustable pressure to the spring behind the ball.
In this design the dovetail retains the part, but the ball detent stops it at the correct position to index.
-How much accuracy does the location require? Yes I know accuracy is a relative word. For indexing mechanisms a tapered pin and matching notch works well when spring loaded. That's what I've used the most. An example would be the Harig type grinding heads and how they hold indexed position.
The ball detent is to just get it in the ball park. This is an interchangeable soft jaw system for a vise. Pins align the two sets of the soft jaws, but the ball detent helps to center in vise. A dovetail lock secures in place.
-A good enough method for approximating location. Ball detents won't provide a lot of accuracy and you're already providing positive location with the pins. Is there something you want to improve with the method/process/dimensions/tooling you've been using? How can I help?
-A good suggestion I had forgotten about. I have sometimes used the CAD models from product manufacturer sites to "extract" data/dimensions from existing designs instead of re-inventing the wheel. I've also used a lot of Vlier products over the years, always with good results. Thans for reminding me larry_g.
-I have the book in front of me (20th edition) and attempted to find the formula under: ball, detent, spring, plunger, and no results. It may be online or in a newer edition but not mine.
Couldn't find anything in my 21st edition either, not saying there isn't anything in there on ball detents but I couldn't find it.
-Mine is coming apart at the binding from use. I'm retired now so don't guess I'll need a new one.
I actually have 4 copies at present but the 21st is the newest. They are dirt cheap on ebay unless you're after a current or almost current edition.
-Bought mine new in 1979 when I was fairly new in the trade, have worn the binding out from constant use. Your 1919 edition must be interesting to thumb through. A lot of line drawings reproduced from pen & ink? Vellum reproductions and onion skin overlays too? Things were designed differently back then. Even handwheels had a vaguely art deco look as industrial designs became more refined during that period. Nice that you found it....or it found you.
I don't think it's a whole lot different in construction to editions from the 40's. It's all printed paper, nice gilt edges, doesn't look like it's ever been in a machine shop, Mr B. H. Stagg who signed the title page must have really looked after it.