Researching how to make my own tool holder (having seen the price of them). The mill I have access to uses an ISO40 taper. ISO. Excellent that's gonna be metric and sensible and... no wait... Wtf. ISO taper angle is 8.2971° (relative to the centre line of the piece).
What uncultured barbarian idiot came up with such a number...
Oh right, it's grandfathered from imperial 3.5" in a foot, or a 7:24 ratio. *Sigh*
Technical debt... Machine shop edition.
@quixoticgeek since you don't cut tapers with that high degree of accuracy required by setting any kind of angles: who cares?
@PalmAndNeedle cos I need to work out how to set that angle on the top slide. and I can't just use a dial indicator to copy an existing taper.
@quixoticgeek Been quite a while since I've done it, and I only ever made decorative tapers (plumb bobs). But my favorite YouTubes maker #Blondiehacks has a great demonstration for the home gamer. https://youtu.be/bZxAYw_-JYA?si=gq5wLhXsNxAjCZUg
@quixoticgeek Hum. Hommmm...
Actually: can you still cut a steeper taper like iso 40 by offsetting the tailstock?
@PalmAndNeedle I don't know. Also it's a shared lathe at a makerspace. If I mess with tail stock alignment, I may not be a popular person...
@quixoticgeek See cold open of said video. Learn how to realign your tailstock.
I did learn that much in my two week turning crash course (pun intended) that's part of the internship you do before the naval architecture studies. 
@PalmAndNeedle well yes. But now we're into the feature creep area of the project...
@quixoticgeek Yes. But all that stuff - dialing in your mill vice, tool post height, tail stock alignment - that's the basic machining skills you need anyway. Kinda like marking out joints and sharpening you edge tools in woodworking.
@PalmAndNeedle completely agree. But anything I do has to be completable in a day. I have to leave the lathe in the condition I find it at the end of the day. So I can't spend 3 days with complex setups. Anything I can do to simplify operations helps a lot here. I'm already likely to need to buy my own chuck, so I can take the work off and keep it all concentric should things take too long. I don't wanna miss the last train cos I was aligning the tailstock.
@quixoticgeek oh, the joy of shared workspaces 
@PalmAndNeedle yep. But given I live in an apartment. It's the best option I have if I want to do machining. It's also a far better set of tools than I might have if it was my own work shop.
@PalmAndNeedle massively so. Makes fixturing that extra bit harder too. I'm hoping if I have my own chuck, I can always take a part off the lathe and put it back without losing concentricity. As long as i or noone else fiddled with the tailstock...
I haven't worked out the same for the mill...
@quixoticgeek yeah, work holding is a wholly different beast between spinning the tool and spinning the work. I don't think there's an easy way out like that on the mill, except for maybe fixturing on the table and leaving the vice clear for other people to use.
It is quite a big beastie. The caveat being that it hopefully works well over the whole width of the table. All too often they do not.
@quixoticgeek Those are the upsides. That, and community. But clear out and square everything away all the time is a drag.