Hello everybody, This is my first post (and a bit of an introduction)::
I have had and use a Taig microLathe for 20+ years and even have/use the milling attachment.
I used this lathe to make a bunch of round things and a few slots for a 20" telescope I built 18 years ago.
Other that building this telescope and a few R/C racing cars, I have little background in machining,
but a lot of background in drafting (CAD, blueprints,...)
So I know how to make the drawings that can be assembled into finished parts,
But little on how to make precision parts.......
Last year I retired from having designed computer chips for 35 years, and I am gifting myself three large telescopes, and as it turns out, gifting myself a machine shop to make them in too.
Right now I am building a 13", a 20", and a 30" telescopes, and while I did build my 20" F/4 DOB with little more than the Taig, hacksaw, file, vise, and drill press. I decided for the 30" and its support requirements I am building; a new set of tooling was going to make my effort go down. So this spring, I got an 8×30 mill (G0730) and to accompany it a G4003G lathe, backed up with a 14" metal bandsaw, and a small table saw.
For me my mill was limited because the structural engineer said the concrete floor would not hold the weight of a Bridgeport on the footprint of the BP. So, limited to "about" 1000 pounds for the mill, I spent months looking at CL, Ebay, ... looking for "as big as possible" but not over 1000 pounds. Clausings, Rockwell made things that fit the bill, it is just there was no readily available supply, on the lathe side, SouthBend,... made lathes with similar floor loadings. But after a couple of months looking, and not wanting to drive 1/2 way across the country, and finally, wanting a working machine not a project to finish before getting to the telescopes; I decided to just buy some new Grizzly stuff.
My initial inclination was that I would be using the lathe and the mill about as much as each other. This has not been the case as of yet. I find myself making many more parts and spending a lot more time on the mill than on the lathe. I think a lot of this has to do with the experience I have had on the Taig, and the fact that the G4003G pretty much runs itself, whereas setting up intricate assemblies in the mill so a hole can be flat faced, drilled, relieved, and tapped in 2 or 3 parts simultaneously is simply a lot harder than making something round.
I happen to need a lot of strange looking parts in order to make the mirror cell for the 30" telescope. Many of these parts articulate on small ball bearings, and they require bearing fits on the race and shafts. Some of these look a lot simpler to make when all you have to do to draw them is a couple of carefully chosen clicks, and mouse movements. Actually taking raw stock metal and making the part fit the blueprint is not often straightforward, especially when one is looking for 0.001 interference fits for the bearings and trying to bore such a hole at 0.2485. I can't tell you how many attempts it took before I figured it out. But sé la vie, it's a good learning experience.
Back to the OPs question: There is no question that the first machine should be the lathe, because a lathe makes things sufficiently round that you cannot make so critically round with any other means (files and drill press). The mill is performing the work of the hacksaw, file, and drill press, but if you are persistent, careful, and attentive, you can generally make acceptable parts without the mill (albeit at higher effort).
