Perfectly fine machines at a fraction of BP price.
All spindle tooling is modified from 30 taper. see SB forum various posts how to do this.
Certainly better than (BP) R8, though a slight bit of extra effort. Use ER40 Collet chuck, or ER32 for less overhang with smaller tools. 30 taper solid collets and arbors are common enough. Most were delivered with 30 taper flush arbors as accessories.
Differences from BP:
Head does not nod.
Turret does not swivel on column.
quill travel = 4" (instead of 5")
HP is either lower speed 3/4HP or higher speed 1HP. (2 different original motor options, not 2 speed motor) I've never seriously bogged 3/4HP down in sensible cuts even with largish tools. Routinely used 4-3/4" dia insert face mill burried in CI when first acquired.
Final drive to spindle is cogbelt
If it comes with the power down/up feed, it is a very strange, but quite effective hydraulic system. Infinitely variable up or down, instant rapid return. But most have parts removed - usually the hydraulic powerpac is missing.
Iron is as good as BP.
I would argue that adjustable taper roller bearings in SB quill are superior. They do need occasional adjustment
Round ram is keyed and gibbed, so if you spend a little time tweaking the clearance to repeat when it is re-positioned, it is as good as a BP DT ram.
Like BP, original mechanical table feed works fine if complete in good shape.
If not, same as BP, put an aftermarket unit on the end of the table.
(My biggest gripe about original SB feed is that it does not have rapid)
smt