Thanks. Those plans are helpful for study. I've seen that photo of the lathes themselves before someplace else. Maybe CNC Zone. I didn't know there was an entire project package.
Notice the lead screw center mounted between the bar ways? The Unimat adopts this also. I can't think of a better way to equalize the traversing force on the carriage. The old fashioned side mounting screw and carriage apron (ala my Atlas 10x24 or any Chinese machine) has to induce a constant twisting force. Plus there's a big elaboration of bearings and pillow blocks to support it all.
For the bar ways I have our favorite Alloy 4142 HT-TGP (heat treated, turned, ground & polished) in mind. 1" diameter is around $26 ea for 24" lengths.
One problem with that design is the ratio of the ways base to spindle height. For maximum stability the ways' width ideally should be 120% of spindle height, which is 1/2 of the swing. For a 4" swing that would be 2.4". This is Goldilock's just right for a small "bar ways" lathe with 3" x 3" bed based on a length of 8020 t-slot aluminum extrusion.
A CNC equipped Sherline with 3.5" swing runs about $2300 delivered, including a computer. Subtract computer and this is still about $1700. Sherline manages to use 135 oz/in stepper motors and free Linux EMC2. This size of stepper is cheap and can be run with recycled computer power supplies ganged in series. There are also several public domain driver board designs available for that class of stepper.
I want to develop a comparable CNC project lathe design that's buildable for about $250-$300 cash outlay. My concept is to use a small stiff CNC router - dozens to hundreds of plans available - to assist with the fabrication. Plus a 1/2" el cheapo drill press.
And small aluminum castings for those who want to avoid the cost of aluminum stock for the headstock, carriage and tailstock.
The Unimats are worth some study in the small lathe class. Quite small actually. 3" swing by 5" between centers for the first ones.
Tony's history shows they changed quite a bit in design composition over time. Cast iron parts to zamac die castings to aluminum die castings...
Consider the reputation Unimats have to this day among model makers. There's a simple reason the mix 'n match materials don't matter in small machines. Relatively large parts are required before differing coefficients of thermal expansion will sum enough to matter.