Excerpt from
https://en.wikipedia.org/wiki/Machine_taper
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ANSI B5.18-1972 specifies some essential dimensions for milling machine spindles and tool shanks using taper sizes 30, 40, 45, 50, 60.
[10] The specifications describe the position of the driving key and flange and the thread of the draw-in bolt that holds the shank in the spindle.
The tooling is referred to as Quick Change; National Machine Tool Builders' Association, 1927; NMTB; American Standard Machine Taper, ANSI B5.18; DIN 2080 / IS 2340; ISO R 290-2583.
[11] There are slight variations in threads and flanges (JIS B 6339: MAS 403); and the European standards (e.g.,
ISO taper) use metric draw threads.
The NMTB tool shanks had the 7 in 24 taper, but they also had a constant diameter tail (pilot) at the end of the shank that was described in the 1927 patent. Subsequent design variations dropped the tail (making the shank shorter) and put a V-groove in the flange that aided automated tool changing. Modern designs started using power drawbars that gripped pull studs (also known as retention knobs) that were screwed into the tool shank rather than screw-in drawbars. The power drawbar would grip the pull stud rather than screwing into the tool shank.
The more modern toolholder designs became known as the Caterpillar "V-Flange", CAT, V-Flange, ANSI B5.50, SK, ISO, International (INT), BT, ISO 7388-1, DIN 69871, NFE 62540. Once again, there are slight variations in the tooling.
[11] Although the basic taper dimensions are the same, there are differences are in the flanges, draw-in thread sizes, and pull studs; the international versions use metric sizes.
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My take on it:
I am not really familiar with the 30, 40, and 50 tapers, I don't have any in my shop, but I think that within one basic size, such as 30, the tapered portion has the same angle and about the same length of taper on all variations. However, all the other options, like drawbar connections, flanges, and other details can be quite variable between brands and styles. Interchangeability can be quite a different matter between manual machines and automatic tool change machines.
