Someone, I think, mentioned 35mm.
If you want to pass something that size through the Headstock mandrel, you need a MT5 bore.
That will come with a larger lathe, apart from the US and UK makes, you are likely to find such things in a secondhand Warco BH600/Chester Craftsman/ Engineers ToolRoom BL12-24, (or their modern equivalents which may well be geared head rather than belt driven).
Those just mentioned, are effectively the same machine in different colours, will swing 12" over the bed, (18" in the removable gap), Induction hardened beds with prismatic ways, and have a Norton gearbox with power feeds for Sliding and Facing.
They do weigh about 300Kg, so your floor could pose a problem. Could you use angle iron to spread the load?
For what I do, my BL12-24 (with VFD) has proved to be quite satisfactory, but if you don't fancy later Chinese machines, you have to look at even older machines, probably ex Industry (heavy wear possibly) or ex school/college (light use but abused). These are likely to put into Restoration man mode before you start the work for which you bought the lathe.
Remember that you can do small work on a big lathe, but not the other way round!
HTH
Howard
Edited By Howard Lewis on 09/01/2017 17:02:52
Edited By Howard Lewis on 09/01/2017 17:12:52